HomeMy WebLinkAboutPUBLIC SAFETY ELEMENT MARCH 1975 *NEW FILE*
PUBLIC SAFETY ELEMENT
MARCH 1975
PUBLIC SAFETY
ELEMENT
06
4 -t .tF OIX
March 1975
Adopted by the Newport Beach City Council
March 10, 1975
Resolution No. 908
PUBLIC SAFETY ELEMENT
NEWPORT BEACH GENERAL PLAN
(Including Safety and Seismic Safety Elements as required by
State Law.)
ADOPTED AND RECOMMENDED FOR APPROVAL BY THE
PLANNING COMMISSION
FEBRUARY 6, 1976
ADOPTED BY THE CITY COUNCIL
March 10, 1976
Insert Resolution No. 908
RESOLUTION NO. 908
A RESOLUTION OF THE PLANNING COMMISSION OF THE
CITY OF NEWPORT BEACH ADOPTING THE PUBLIC SAFETY
ELEMENT OF THE NEWPORT BEACH GENERAL PLAN
WHEREAS , a phase of the City ' s General Plan Program
has involved the preparation of a Public Safety Element ; and
WHEREAS , said Public Safety Element sets forth
objectives and supporting policies which will serve as a guide
for the future planning and development of the City; and
WHEREAS , pursuant to Section 707 of the City Charter
of the City of Newport Beach , the Planning Commission has
held public hearings to consider the adoption of the Public Safety
Element of the Newport Beach General Plan .
NOW , THEREFORE , BE IT RESOLVED that the Planning
Commission does hereby adopt and recommend to the City Council
the Public Safety Element of the Newport Beach General Plan described
above , a copy of which is on file in the Newport Beach Community
Development Department.
Regularly passed and adopted by the Planning Commission
of the City of Newport Beach held on the . 6th day of
February 1975 .
AYES :, Agee , Beckley , Hazewinkel ,
Heather, Parker, Seely , Williams
NOES : None
ABSENT: None
rman
S retar
RESOLUTION NO . 8449
A RESOLUTION OF THE CITY COUNCIL OF THE
CITY OF NEWPORT BEACH ADOPTING THE PUBLIC
SAFETY ELEMENT OF THE NEWPORT BEACH GENERAL
PLAN .
WHEREAS , a phase of the City ' s General Plan Program
has involved the preparation of a Public Safety Element; and
WHEREAS , said Public Safety Element sets forth
objectives and supporting policies which will serve as a guide
for the future planning and development of the City ; and
WHEREAS, the Planning Commission of the City of
Newport Beach , pursuant to Section 707 of the Newport Beach City
Charter, has held a public hearing to consider the adoption
of the Public Safety Element as a part of the City ' s General Plan
and has adopted and has recommended that the City Council
adopt said element; and
WHEREAS , the City Council has conducted a public
hearing to consider the adoption of the Public Safety Element as
a part of the City ' s General Plan .
NOW , THEREFORE , BE IT RESOLVED that the City Council
of the City of Newport Beach does hereby adopt as a part of the
General Plan the Public Safety Element described above, a
copy of which is on file in the office of the City Clerk.
ADOPTED this 10th d.ay of March 1975 .
Mayor
ATTEST: VPO
City Clerk
41 P0 FL.
TABLE OF CONTENTS
Page
Introduction 1
Purpose and Scope 2
Section I — Geologic Hazards 5
Seismicity 6
Slope Stability 12
Expansive and Collapsible Soils 14
Erosion and Siltation 16
Excessive Settlement and Subsidence 18
Section 2 — Flood Hazards 19
Hazards 19
Santa Ana River 21
San Diego Creek 21
Delhi Channel 22
Buck Gulley, Morning Canyon and Jasmine Creek 22
Reservoirs 23
Tsunami, Seiche and Storm Surge 24
Section 3 — Fire Hazards 26
Fire Hazards Catagories 31
Risk Evaluation and Mitigation 31
Disaster Planning 33
Risk Reduction Program 37
INTRODUCTION
Natural occurrences, such as the San Fernando earthquake in 1971, the tsunami damage
to Crescent City in northern California in 1964, and the flood damage throughout Orange
County due to the relatively minor 1969 storms, forcibly remind us that we live in an active
and potentially hazardous environment.
The first three sections of the Public Safety Element identify the major potential natural
physical hazards which could affect the Newport Beach planning area. Maps located in
each of these sections delineate areas of concern in terms of risk from Geologic, Flood
and Fire Hazards. A review of the adopted Emergency Operation Plan for the City follows
the aforementioned sections.
The final portion of the Element describes the method by which the City will address
potential public safety hazards. It is in this final portion of the Element that the City
establishes the "level of risk" it deems acceptable and the risk reduction program policies
designed to achieve this level.
PURPOSE AND SCOPE
The purpose of this Element is to introduce safety considerations in the planning process
in order to reduce loss of life, injuries, damage to property, and economic and social
dislocation resulting from fire, flood, and dangerous geologic occurrences. It is intended
that this Element serve as a review of the natural physical hazards in the Newport Beach
planning area, and provide for public safety considerations in the physical development of
the City of Newport Beach. This Element does not include a comprehensive disaster plan,
civil defense plan, crime prevention or other safety programs since the General Plan is a
guide to the physical development of Newport Beach and does not include such
11governmental-program" planning. This Element is intended to provide a basis for
reducing the hazards to public safety resulting from the geographical setting and physical
development of the City of Newport Beach.
It is further intended that this Element satisfy the State requirement that local General
Plans contain a "Safety Element", q'Seismic Safety Element" and identify areas subject to
flood hazard. Section 65302 of the Government Code states, in part, that the General
Plan shall include:
1. "A safety element for the protection of the community from
fires and geologic hazards including features necessary for
such protection as evacuation routes, peak load water
supply requirements, minimum road widths, clearances
around structures, and geologic hazard mapping in areas
of known geologic hazard."
2. "A seismic safety element consisting of an identification
and appraisal of seismic hazards such as susceptibility to
surface ruptures from faulting, to ground shaking, to
ground failures, or to the effects of seismically induced
waves such as tsunamis and seiches.
2
The seismic safety element shall also include an appraisal
of mudslides, landslides, and slope stability as necessary
geologic hazards that must be considered simultaneously
with other hazards such as possible surface ruptures from
faulting, ground shaking, ground failure and seismically
induced waves."
This Element includes consideration of natural physical hazards in three major sections:
Section I - Geologic Hazards
Section 2 - Flood Hazards
Section 3 - Fire Hazards from Undeveloped Areas
Sections 1 and 2 are based on the "Geologic-Seismic Study", October, 1972, conducted
by Woodward-McNeill and Associates under contract with the City, with additional input on
flood hazards from the Coast and Geodetic Survey, the Army Corps of Engineers, and
Moffatt and Nichol, Engineers.
Section 3 has been developed in conjunction with the Newport Beach Fire Department.
The risks to public safety from fire hazard within existing urban structures will not be
considered in this Element. Appropriate sections of the Community Facilities Element will
address this issue in terms of facilities, locations, response times and other associated
factors.
3
The last section of this Element includes a "Risk Reduction Program which contains those
land development regulations, restrictions, and other actions which are considered by the
City of Newport Beach to be reasonable and practical, in order to assure that the future
development of the City does not result in increased risk to life and property from natural
environmental hazards.
4
SECTION 1 - GEOLOGIC HAZARDS
The City of Newport Beach is located along the southwesterly edge of the Los Angeles
basin adjacent to the Pacific Ocean. The City will be affected by both regional and local
geologic hazards resulting from events that will occur as a result of geologic processes.
The purpose of this section is to identify those hazards that will effect the City of Newport
Beach. Appendices A through D relate to geologic hazards identified within this section
and are attached.
Seismici
The potential for severe damage and loss of life resulting from earthquake activity exists
within the City of Newport Beach as it does throughout Southern California. The City could
be faced with several major seismic hazards, such as 1) Ground Shaking, 2) Ground
Failure, 3) Ground Displacement 4) Tsunamis and 5) Seiches. The potential hazard from
tsunamis and seiches are discussed as a part of Section 2 of this Element. The following
discussion of seismic hazards from the "Planners Guide to the Seismic Safety Elemenr',
prepared by the Association of Engineering Geologists describes the remaining
aforementioned potential hazards:
"Experience has shown that in most areas of the world, including
California, fault movements during historic time have nearly always
occurred on already existing faults with evidence of geologically recent
movement. Since earthquakes are the result of movement along faults,
in attempting to predict future earthquakes and fault movement within - or
near - a particular site, consideration should be given not only to the
seismic record during historic time, but also to the presence of any faults
with evidence of geologically recent movement.
5
The most widespread effect of an earthquake is ground shaking. This is
also usually (but not always) the greatest cause of damage. Structures
of all types, including engineered structures and public utility facilities, if
inadequately constructed or designed to withstand the shaking force,
may suffer severe damage or collapse. The vast majority of deaths
during earthquakes are the result of structural failure due to ground
shaking. Most such deaths are preventable, even with present
knowledge. New construction can and should be designed and built to
withstand probable shaking without collapse. The greatest existing
hazard within the state is the continued use of tens of thousands of older
structures incapable of withstanding earthquake forces. Knowledge of
earthquake-resistant design and construction has increased greatly in
recent years, though much remains to be learned.
A second effect of earthquakes is ground failure in the form of landslides,
rock falls, subsidence, and other surface and near surface ground
movements. This often results in complete loss of strength of water-
saturated sub surface foundation soil ("liquefaction") such as occurred
near the Juvenile Hall in the 1971 San Fernando earthquake and in the
massive Turnagain Arm landslide in Anchorage during the 1964 Alaska
earthquake. Most such hazardous sites can be either avoided or
stabilized if adequate geologic and soil investigations are utilized.
Another damaging effect of earthquakes is ground displacement (surface
rupture) along faults. Such displacements of the earth's crust may be
vertical, horizontal, or both and may offset the ground by as much as 30
feet (as in 1857 in Southern California). It is not economically feasible to
design and build foundations of structures (dams, buildings, bridges) to
remain intact across such zones. Fault zones subject to displacement
are best avoided in construction. In addition to regional investigations
necessary to the basic understanding of faults and their histories,
detailed site investigations are needed prior to the approval of
construction in any suspected active fault zones. Utilities, roads, canals,
and other linear features are particularly vulnerable to damage as a
result of ground displacement."
A seismic hazard map indicating the general locations and extent of areas subject to
seismic hazards in Newport Beach is attached (Figure 1). A more detailed preliminary
analysis is provided in the "Geologic-Seismic Study" prepared for the City by Woodward
McNeill and Associates.
6
ACTIVE FAULTS IN SOUTHERN CALIFORNIA
Numerous definitions for active faults have been proposed. Probably the most
encompassing definition is that of the California Council on Intergovernmental Relations in
the General Plan Guidelines, September 1973, which is:
"(Active Fault): A fault that has moved in recent geologic time and which
is likely to move again in the relatively near future. For geologic
purposes, there are no precise limits to recency of movement or
probable future movement that define an active faulf. Definitions for
planning purposes extend on the order of 10,000 years or more back and
100 years or more forward. The exact time limits for planning purposes
are usually defined in relation to contemplated uses and structures."
This definition is used in this section for classifying the faults described in alphabetical
order, as follows:
Newport-Inglewood Fault Zone:
The Newport-Inglewood Fault Zone is a series of an echelon northwest-trending, vertically-
dipping faults extending from the southern edge of the Santa Monica Mountains
southeastward to the offshore area near Newport Beach. From north to south the fault
segments are: 1) Chamock Fault; 2) Overland Avenue Fault; 3) Inglewood Fault; 4)
Potrero Fault; 5) Avalon-Compton Fault; 6) Cherry Hill Fault; and 7) Seal Beach Fault.
Numerous recent shocks of 4.0 magnitude or greater, as well as the historic 6.3 magnitude
Long Beach Earthquake in March 1933, have been generated within this fault zone and
suggest an active seismic history. Although there has been no observed ground surface
displacement associated with the Newport-Inglewood Fault Zone, there may have been
subsurface fault displacement of approximately seven inches associated with the October
21, 1941, earthquake (magnitude 4.9) and the June 18, 1944, earthquake (magnitude 4.5).
This fault zone could generate a 7.0± magnitude maximum credible earthquake. This is
the only active fault within or immediately,adjacent to the City of Newport Beach.
7
Norwalk Fault:
The Norwalk Fault is suggested to be a high-angle reverse fault (Appendix A-3) dipping to
the north. The fault is approximately 16 miles long, roughly trending northwest, and has
an arcuate trace between Buena Park and Tustin. Microseismic activity along the Norwalk
Fault is high and a 4.7 magnitude earthquake occurred on July 8, 1929, which caused
significant damage in Whittier and Norwalk. Richter(1958) suggests that the fault.
Raymond Fault Zone:
The northeast-southwest trending Raymond Fault Zone has a length of approximately 16
miles and extends from the foothills of the San Gabriel Mountains in Sierra Madre to the
Adams Hill area of Glendale. The fault serves as a ground water barrier and is coincident
with an obvious topographic scarp along much of its extent through Pasadena. Geologic
evidence suggests there has been a minimum of 222 feet of vertical displacement along a
portion of the fault near Raymond Hill since Miocene time, and that clay gouge along the
fault within the alluvium serves as an aguiclude. Age dating of soil material which fills
cracks probably caused by the latest movement of this fault suggests that the fault moved
approximately 3,000 years ago. The maximum credible earthquake expected from the
Raymond Fault is magnitude 6.8.
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San Andreas Fault Zone:
The San Andreas Fault Zone extends from the Gulf of California northward to the Cape
Mendocino area where it continues northward along the ocean floor. The fault plain is
essentially vertical and has a right lateral sense of movement. The total length of the San
Andreas Fault Zone is approximately 750 miles. In 1857, a magnitude 8.0± earthquake
occurred along a 225-mile length of this fault between Cholame and San Bernardino. This
seismic event is the most significant historic earthquake in Southern California history.
The length of this right lateral fault and its active seismic history indicates that it has a very
high potential for large-scale movement in the near future (magnitude 8.0±), and should be
considered important in land-use planning for most cities in California.
San Fernando Fault Zone:
Fault segments that were demonstrably Involved in the February 9, 1971, San Fernando
Earthquake (magnitude 6.4) are, for the most part, east-west trending thrust faults with
associated left lateral movement. The ground surface ruptures occurred on little known
preexisting faults in an area of low seismicity and previously unknown historic ground
displacement. The zone of displacement was approximately 12 miles long and had a
maximum of three feet vertical movement. The fault plane dips northward at an angle of
approximately 55 degrees from the horizontal. The earthquake epicenter of the February
9, 1971, seismic event was near the community of Newhall The recurrence interval for the
San Fernando Fault Zone is estimated to be approximately 200 years. The Santa Susana
Thrust extends westward from the area of the San Fernando Fault Zone. This thrust has
been classified as potentially active by some geologists based on evidence which
suggests that movement has occurred within the past two million years. In its western
portions, there is evidence that the fault plane has been folded and would therefore
10
probably not have renewed movement.
San Jacinto Fault:
The San Jacinto Fault is a northwest-trending complex series of right-lateral faults
extending from the eastern San Gabriel Mountains south through the Borrego Valley. This
fault appears to merge with the San Andreas Fault southeast of Pearblossom. Seismically
one of the most active faults in the state, the San Jacinto has been the origin of many
small and moderately large historic earthquake shocks. Ground surface displacement has
occurred along the fault, the most recent being in Borrego Valley in San Diego and
Imperial Counties on April 8, 1958, during a magnitude 6.5 earthquake.
Slope Stability
The stability of slopes is an important planning consideration for existing and future
development within the City. Slope failures either gross or superficial can result in a
potential hazard to life and limb, or endanger public and private property. The types of
slope failures that may occur within the community will probably be, 1) landslides, 2) mud
flows, 3) creep and in some cases 4) rock fall. (See definitions in Appendix D). In any
planning consideration, the more important factors are generally, the inherent strength of
the earth material of which the geologic formations are comprised, the moisture content of
these materials, and the attitude of the bedding within the materials.
Within the Newport Beach planning area and land adjacent to it, the areas of low slope
stability include areas in the San Joaquin hills and the bluff areas throughout the City. As
shown on Figure 2, these areas of low slope stability occur primarily in areas of moderate
to steeply-sloping terrain.
12
PLKC SAFE[Y
NEWPORr BECH
SLOPE SYM3LW
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Expansive and Collapsible Soil
Expansive soils are generally defined as those soils that exhibit a change in volume wh6n
the moisture content of the soil is varied. The degree of expansion is most generally
related to the magnitude of this change and expressed as ranging from very low to very
high. A collapsible soil is usually considered as a loosely packed or open structured soil
that exhibits a sudden loss of volume upon the addition of a significant quantity of water.
Expansive and collapsible soils usually have an adverse effect on building foundations
often resulting in negative impacts on the entire structure.
Movements may vary under different parts of a -building with the result that the
foundations crack, with vertical displacement, causing various structural portions of the
building to bg destroyed. In the extreme case windows and doors are warped so that they
do not function properly, rendering the building useless for its intended occupancy. These
problems can be identified and controlled by proper engineering and construction
practices. Figure 3 divides the City into categories of expansive soil probabilities.
Collapsible soils are not prevalent within the City; however, they do occur locally, and
should be addressed on a project-by-project level by all geotechnical studies conducted
within the City.
14
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Erosion and Siltation
Soil erosion occurs as a result of the action of wind and water and is a geologic process
commonly referred to as mass wasting. While wind erosion may have some localized
significance, it is not a major natural hazard. Erosion as a result of running water is an
acute potential risk within the City, especially during periods of heavy rainfall and runoff.
The erosion of soils can undermine structures or damage slopes and could result in
property damage and/or the loss of life and limb.
Siltation resulting from the deposition of eroded earth materials also presents an acute
potential risk. Due to the City's geographic locations, regional as well as local siltation
should be considered as a part of this hazard. Inundation of structures both public and
private can reduce the capacities of drainage structures and, thereby reduce capacities for
flow and storage of flood waters.
Erosion and subsequent siltation are magnified during new construction where the
removal of natural ground cover occurs.
Periodic dredging of Newport Bay has been required to remove depositions of silt resulting
from erosion occurring principally outside of the City. The majority of this silt enters the
bay through San Diego Creek and comes from erosion within that creek's watershed.
Figure 4 indicates the general locations of potential erosion and siltation-related problems.
16
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Excessive Sefflement and Subsidence
With the exception of areas adjacent to the Upper Bay, soils within the Newport Beach
planning area are generally considered to be not compressible and, therefore, not subject
to excessive settlement. In Big Canyon and in the northeasterly portion of the Upper Bay
lowlands, soft, compressible silts and clays are prevalent. The introduction of fill materials
and development of these areas could result in excessive settlement and damage to
structures.
Subsidence is a local mass movement of earth materials which are displaced vertically
downward causing large-area settlements.
In the Woodward-McNeill study, no areas of significant subsidence problems were
identified within the Newport Beach planning area.
Summation
Geologic hazards require identification and evaluation by qualified professionals if they are
to be dealt with satisfactorily. As a first step in this program, the City retained the firm of
Woodward-McNeil 11 and Associates to prepare a preliminary "Geologic-Seismic Study"
of Newport Beach.
The County of Orange in cooperation with the California Division of Mines and Geology
has been preparing a series of Geologic maps for the entire county based on the most
recent data available. Subsequent to its publication, the City will incorporate and utilize
this data as required to update our existing code enforcement relating to geologic hazards.
18
SECTION 2 - FLOOD HAZARD
Flooding has been one of the costliest natural hazards in California. National statistics
have shown this state ranking as one of the major flood problem areas within the nation.
Flooding in the Newport Beach planning area though has not historically'been as severe a
problem as it has within other local,jurisdictions.
This section of the Public Safety Element delineates (Figure 5) flood-prone areas within
the City, and evaluates the potential public safety hazard. This Element deals only with
areas of potential major damage from a severe storm. Localized instances of inundation,
such as that which occurs in the low-lying areas of the City during more normal storms or
high tides, will not be addressed.
Policies directed toward achieving an acceptable "level of risk" to the public from
inundation are included as a part of the "Risk Reduction Programs" located in the last
portion of this Element.
19
SAFEFY RENAM
NEWPOW BMCH
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Santa Ana River Area
The potential for loss due to flooding is greatest in the low-lying area immediately adjacent
to the Santa Ana River. During the 1969 storms of January and February (35-year flood)
the river 5 waters came close to approaching the capacities of protection measures.
Considerable pollution of the beach and river itself occurred.
The Santa Ana River drains approximately 3,200 square miles in San Bernardino, Orange,
and Riverside Counties. Obviously, the risk from flood damage due to the river
overflowing is beyond the ability of Newport Beach to control.
A recent study by the United States Army Corps of Engineers has indicated that the risk
along the Santa Ana River can be lessened through several corrective measures
upstream. The actual disposition of this study and the protective measures to be used are
still unresolved. Until adequate measures are taken upstream, the risk will remain in
Newport Beach. T e construction of the major corrective measures presented in the
Army Corps of Engineer's study, if approved, would commence in 1980, with completion
taking eight to ten years.
San Diego Cree
The San Diego Creek Watershed encompasses approximately 118 square miles of
Orange County draining southwest to Upper Newport Bay. The Creek has historically
been the cause of considerable flood damage. The —g—g storm's damage along this creek
included the washing out of MacArthur Boulevard with associated damage to adjacent
roads and agricultural areas, and the deposition of massive amounts of silt into the Upper
21
Bay.
The construction of facilities for the off-ramps of the Corona del Mar freeway and
MacArthur Boulevard interchange should eliminate the potential flood risk in terms�of the
highway.
The low-lying lands adjacent to the San Diego Creek and the Upper Bay will continue to
be flood-prone areas.
Delhi Channel Area
This channel area is located at the northwest edge of the Upper Bay. A potential for flood
damage within the area was identified by Woodward-McNeil and Associates in 1971. The
United States Army Corps of Engineers confirmed this finding in 1972 ("Flood Plain
Information — San Diego Creek and Peters Canyon Wash"). Currently the Land Use and
Open Space Elements indicate this area for open space uses.
Buck Gully, Morning Canyon and Jasmine Creek
These areas were identified for the City as possible flood risk locations in the 1971
Woodward-McNeill and Associates "Geologic Seismic Study". For the most part these are
areas of natural drainage to the bay or ocean, some of which have been improved through
public or private projects.
All of these locations have been designated on the Land Use Element of the General Plan
for"Recreational and Environmental Open Space."
22
Bia Canyon Reservoir
In order to fulfill State requirements a detailed inundation study was prepared by James N.
Montgomery, Consulting Engineers, Inc., for areas downstream of Big Canyon Reservoir.
This was accomplished in order to provide guidance to public safety agencies for the
development of safety measures in the event of flooding from a partial or total failure of the
dam. This critical reservoir is used to store water for domestic consumption, with the
reservoir located within a 1200? acre watershed which drains to Upper Newport Bay.
The "Inundation Study for Big Canyon Reservoir -- Orange County, California", indicated
the general area of potential risk which is delineated on Figure 5.
23
Tsunami, Seiche and Storm Surcie
In October of 1974 the Coast and Geodetic Survey indicated to the City that shoreline
properties and the islands of the Lower Bay were subject to potential flood hazard from
storm surge and tsunamis. A tsunami is a sea wave generated by a sub-marine
earthquake, major landslide, or volcanic action. These sea waves are long, powerful, low
waves which in the open sea create relatively few problems. it is upon their approach to
the coastline that tsunamis, because of coastal configurations or bottom topography, can
become high waves or strong currents, both of which are capable of causing major
damage.
The risk to the public safety of tsunamis resulting from landslides or volcanic action has
been evaluated and found to be extremely remote within the City. A Woodward-McNeill
and Associates report prepared in 1971 as background information for this Element of the
General Plan stated that the City is afforded a degree of protection (from tsunamis) by
coastal islands with the chance for major damage to the coastal areas or harbor entrances
not great, and negligible for inland bay areas.
In October of 1974 the firm of Moffatt and Nichol, Engineers, under contract with the City,
again reviewed the potential hazard to the public safety in Newport Beach from a projected
1 00-year Tsunami occurrence. Their report, "A Preliminary Study of Flood Probability at
Newport Beach" stated that the projected 100-year Tsunami would have less effect than
astronomical tides and even the highest of these tides is below bulkhead elevations.
Potential flood hazard from storm surge was also identified as a risk to the public safety by
the Coast and Geodetic Survey. Moffatt and Nichol reviewed this potential occurrence
and their report stated:
"...provided an adequate width beach berm at present day elevations is
24
maintained, large scale inundation of City's oceanfront by storm surge and
accompanying waves would not occur.
Furthermore, in the interior waterways, the bulkhead elevation provides
adequate freeboard for estimated possible storm surges within the Bay."
Based on this information there does not appear to be a flood hazard for either the lower
bay or shoreline areas.
A seiche is the oscillation of sloshing of water in an enclosed body of water caused by
seismic activity or landsliding. Due to the small surface area of the bodies of water within
the City, seiches do not represent a potential hazard to the public safety.
25
I
SECTION 3 - FIRE HAZARDS
It is the intent of this section of the Public Safety Element to review undeveloped high fire
hazard locations within the Newport Beach planning area. This Element will not deal with
fire protection within the developed areas of the City. The Community Facilities Element
will address fire stations, their locations, facilities for services, and response times to
potential fire risks within urban structures. The undeveloped areas of fire risk, along with
existing programs designed to achieve low levels of risk to the public safety, have been
—identified in this Element with the assistance of the Newport Beach Fire Department.
A majority of the City of Newport Beach has undergone or is in the process of
urbanization. Thus, only a limited number of undeveloped fire risk areas remain within the
City's planning area, as indicated on Figure 6. Yet, this urbanization introduces people in
close proximity to fire hazard areas and results in an increased public safety hazard. This
hazard is further increased by the desires of Newport Beach citizens to maintain natural
parks and open areas.
The problem of high fire risk from undeveloped areas has a seasonal aspect. While the
potential for fire exists throughout the year, the most acute problems of high fire hazard
exist in the late summer and fall of every year. It is at this time that grasses, brush, and
natural ground cover, which have grown throughout the winter and spring, become dry and
volatile. These climatic conditions are often accentuated by very hot-dry Santa Ana winds
which decrease the humidity and increase the potential spread and intensity of local fires.
This type of wind condition can cause fires to whip through areas at many times the
normal rate.
26
The probability of natural occurrence of fires within the areas designated by Figure 6 would
be evaluated as low and not an acute problem. It is because of the close proximity of
residential developments and the introduction of people to these undeveloped areas that
risk to the public safety increases. People through carelessness or accident' create a
majority of damage to natural areas and cause an increase of fire risk from these areas.
The problems associated with fire risk locations are accentuated when dwellings with
wooden shake roofs and close or limited spacing between units are located in close
proximity to fire hazard areas. This has been identified by the Fire Department as
historically a problem and one which will remain as long as development patterns, such as
this, exist within the City.
Fire Hazard Cate-gories
In Figure 6 three categories of fire risk have been identified for the existing state of
development in Newport Beach. The general characteristics of each category vary due to
access, type of combustible materials and other associated factors. The factors involved
in each rating and control measures are described below.
Category 1:
This category indicates locations of probably the highest fire risk within the City. They are
characterized as very dry and this condition is accentuated by the fact that these are also
very rugged locations. The land within this category is classified as fast propagating
natural areas of high fire hazard. In addition this designation generally denotes land in
steep sloping terrain that is too rugged to clear with equipment.
Much of the land which falls within Category I is designated as Recreational and
Environmental Open Space by the Land Use Element of the General Plan. This is an
indication that natural fire risk conditions will continue into the future.
27
Category IL
This potential high risk fire category has been designated in four areas within the City:
I. Buck Gully
2. Morning Canyon
3. Big Canyon
4. St. James Road area
These four locations are characterized as containing both domestic and natural vegetation
growth. They are generally 'greener than Category I containing more combustible material
and are identified as areas which burn readily. Another major factor in so designating
these sites is that access to the interior of each is not readily available and not possible
through conventional means.
Three of the aforementioned locations (Figure 6) are designated for Recreational and
Environmental Open Space by the Land Use Element of the General Plan. The Open
Space and Recreation Element further proposes that the canyons as they run through
Corona del Mar from the beach to the San Joaquin Hills be maintained as natural open
space, by public acquisition of land in fee or by easement. This is an indication that the
high fire risk of the present will continue. Future acquisition through either method should
be coupled with a sound risk management effort.
Category III:
This category contains a majority of the remaining undeveloped land throughout and
adjacent to the City. It is a characteristic of these areas that they are fired more often than
either of the previous categories, yet because of their location, they are not deemed to be
as potentially hazardous to the public. This is due to a higher containment factor created
28
by access and fire breaks. These high fire hazard areas for the most part are cleaned of
cover twice a year by their owners or by contract crews under the direction of the Fire
Department.
Fire breaks are also designated on the Fire Hazards Map (Figure 6). These are linear
strips where the natural vegetation has been removed or reduced. Several of these fire
breaks have been cut and are maintained by private land owners; others by the Parks,
Beaches and Recreation Department or contract crews under the direction of the Fire
Department. These fire breaks form an integral portion of the overall Fire Department risk
reduction program.
29
PUBLIC SAFEW ELGVEq
NEWPORT BEACH
POTgqW FRE HAZARD AREAS
CATEGORY 1:F`=M"JAWML Ft..
Mil 1CM1111CIM.=�9"*RHAIM 1 ;11111 Met
M It"DILY. — I I
R=�tMOINIUM MD Mi
CATEGORY 2:`wmwm au
�.Mclft"N.ol"im,a mc"s
CATEGORV`3:
FIRE PREAKS
N -1
/C:
IN�—J j
Ha
fjrjau I ww
figure 6
Risk Evaluation and Mitigation
A majority of the areas designated as fire risk locations are planned for urbanization within
the framework of the General Plan. Several locations, though, previously mentioned, are
slated to remain in a natural state for environmental or aesthetic reasons.
It is because of the intensity of development adjacent to Categories I and 11 and problems
associated with and within these areas, that potential loss is greatest. Loss in these areas
could include the vegetation cover and structures adjacent to these areas. Without plans
for replanting in case of fire occurrence the potential for soil erosion exists subsequent to
an area being fired.
The potential loss in Category III is lower, due to: 1) the natural cover in these areas being
of a lesser nature, and 2) the ability of public services to address the problem being
greater through existing programs and access.
The City's Fire Department and Parks, Beaches and Recreation Department provide for
risk mitigation measures in primarily two forms: 1) physical action measures, and 2)
educational programs.
The City is Involved in primarily two physical action programs intent on removal or
lessening of combustible material on a particular site. Involved in this are twice-yearly
removals of brush through a 'teed abatement program. The other is the development of
operational fire breaks strategically located throughout the City (Figure 6).
The City is also involved in educational programs, most notably the Junior Fireman
Program. This effort is aimed toward elementary school children throughout the City. The
dual goal of this program is to establish rapport with the children and improve the
understanding of school age children of both the Fire Department and potential fire
31
problems. In addition to this, the Fire Department also addresses local groups on
fire-associated problems within the City.
32
DISASTER PLANNING
The City of Newport Beach has an adopted Emergency Operations Plan which is currently
being reviewed by appropriate State agencies. This portion of the Element will evaluate
this emergency plan in terms of the existing and future physical development of the City
and the natural physical hazards identified in the previous sections of this Element.
Emergency Operations Plan
The adopted Newport Beach Emergency Operations Plan was prepared in accordance
with Federal, State and County guidelines, and developed to meet the particular needs of
the community. Primarily the plan provides for emergency operations for two types of
occurrences, these being civil emergencies and natural disasters. As this Element
addresses safety in terms of physical development, no attempt has been made to review
plan proposals for civil emergencies.
The Emergency Operations Plan provides Newport Beach with a basic framework for
reaction to disasters in terms of authority, responsibilities, and location of critical facilities
and services. The purpose of the plan is stated as follows:
Ill. Provide a basis for the conduct and coordination of
operations and the management of critical resources during
emergencies;
2. Establish a mutual understanding of the authority,
responsibilities, functions, and operations of civil government
during emergencies;
3. Provide a basis for incorporating into the city emergency
organization non-governmental agencies and organizations
having resources necessary to meet foreseeable emergency
requirements."
The Emergency Operations Plan recognizes that the impact of earthquake, fire, and flood
grows larger as areas of high-risk land are used to keep up with urban growth. Any of the
33
aforementioned natural occurrences would tax the resources of a single governmental
entity; therefore, inter-jurisdictional mutual-aid programs are provided for. As adopted, the
Newport Beach Emergency Operations Plan prepares for, and conducts operations in
order to accomplish the following objectives:
1. Provide for the continuity of government.
2. Provide a basis for direction and control of emergency
operations.
3. Save lives and protect property.
4. Repair and restore essential systems and services.
5. Provide for the protection use, and distribution of remaining
resources.
6. Coordinate operations with the civil defense- emergency
service organizations of other jurisdictions.
In some of the emergency situations discussed previously, as natural hazards to the public
safety, the potential loss from the occurrence of hazards can be substantially reduced
through an effective warning system coupled with effective evacuation procedures.
Tsunamis and potential flooding from the Santa Ana River are examples of risks where
there will be an advance warning. Other-emergencies potentially could occur without
advance warning, thus requiring mobilization and commitment of emergency organization
after the onset of the occurrence.
Evacuation Routes:
Evacuation route analysis is not a part of the Emergency Operations Plan. For the most
part, the plan addresses civil emergencies and not natural occurrences in terms of
evacuation routes. The Chief of Police is responsible for traffic control services.
The value of a potential evacuation route is dependent on several factors; among these
are: 1) the type of hazard occurrence, 2) the degree of severity and the location of the
34
occurrence, and 3) the mode of evacuation. Generally, the older areas of the City have
the highest degree of potential problem during an evacuation. The harbor islands, portions
of the Balboa Peninsula, the West Newport Area, Cameo Highland and Cameo Shores
have single access to major evacuation routes. This problem is further accentuated by the
desirability of many of these areas for public recreation. Figure 7, which follows,
delineates these potential problems. The Master Plan of Streets and Highways indicates
several future projects such as the new bay bridge and the realignment of Pacific Coast
Highway in West Newport which will improve existing conditions.
35
PUBUC SAmy aENW
NEWPM WCH
MAJOR EVACUo4flON ROUTES
& POTEWL HAZARD
INTENSIVELY USED AREA'S
ITE
M� SINGLE EVACUATION ROirE
r-----1 DUAL EVACUATION ROUTE
�\ v
71-
Ul \ICE
I y
figure 7
RISK REDUCTION PROGRAM
A hazard free environment does not exist. Natural and/or man -made hazards of some
kind or degree are and will always be present. The preceding sections of this Element
have attempted to identify, delineate, and evaluate risks from natural hazards, along with
an evaluation of risk mitigation measures currently in effect.
The guidelines for the preparation of both the Seismic Safety and Safety Elements
(combined in this Element) prepared by the California Council on Intergovernmental
Relations suggest that each local jurisdiction go beyond the aforementioned to define an
acceptable level of risk for its citizenry. The thought of an acceptable risk is alien to many
people. The natural reaction is to state that no risk is acceptable, yet every day, through
the course of normal actions, people expose themselves to risks at a variety of levels.
These are risks willingly taken such as driving, that people take to derive benefits. Such a
risk can be mitigated by rules, regulations, and safety equipment.
The acceptability of a risk by the general public is dependent on the nature of the risk.
People generally are more willing to accept higher risk from situations such as driving that
they wish to engage in. There are three major risks to the public safety which served as
criteria for establishing priority action areas:
I. Injuries and loss of life
2. Damage to property
3. Economic and social dislocation.
The risk to the public from societal disruption such as the long- term impacts of a major
earthquake cannot be adequately dealt with at the local level and must be addressed by
regional, state and federal agencies.
37
The primary concern of the Public Safety Element and the City of Newport Beach is in
terms of risks to person and personal property. In the context of the Public Safety Element,
the problem of risk is one of public policy and the appropriate allocation of resources to
mitigate potential hazards. The basic premise of this Element has been to provide for
safety considerations in plans for the physical development of Newport Beach. Toward
this end areas of critical concern are listed below:
Geologic Hazards
• High occupancy earthquake hazardous old buildings
• Medium-and high-rise buildings
• Concentrations of dependent populations
• Vital facilities
• Seismic unsafe public and quasi-public facilities
• Disaster response
• Low occupancy earthquake hazardous buildings
• School earthquake safety programs
Flood Hazards
• Developed areas of potential inundation
• Undeveloped areas of potential inundation
• Flood insurance education programs
Fire Hazards
• High natural fire hazard areas
• Weed and brush abatement programs
• School education programs
It is through the adoption and implementation of this Public Safety Element that Newport
Beach establishes the level of risk it deems as acceptable.
38
The following "Risk Reduction Program is intended to provide the maximum reasonable
mitigation of natural physical hazards to life and property in Newport Beach.
Risk Reduction Program
General:
1. The City shall require Environmental Impact Reports for any development within
areas of natural physical hazard, as defined in this Element; said E.I.R.'s to
include detailed assessment of the hazards and a comprehensive mitigation
program.
2. The City shall require complete studies of the siting and construction of
emergency/critical facilities; new emergency/critical facilities shall not be
constructed in areas of high natural physical hazards.
3. The City shall support the development concept of clustering structures and
facilities in favorable areas, restricting development in steeply-sloping
topography, on bluff edges, erodible areas, and other areas of high natural-
physical hazard.
Geolo-gic Hazards:
1. The City shall adopt a new grading ordinance, including more-stringent erosion
and siltation control and geologic hazard mitigation requirements.
2. The City shall require geologic and seismic studies as an integral portion of all
Environmental Impact Reports with detailed mitigation measures for any
development in areas of high potential hazards.
3. The City shall critically review proposals for development in expansive and
collapsible soils and will "require detailed geotechnical studies prior to
development to assure mitigation of risk.
39
4. The City shall require building siting and design to be compensatory with
geologic hazards which reflect varying requirements based on risk, location and
type of occupancy, and shall be safe and stable for its intended use.
5. The City shall encourage and participate in future studies of faults and seismic
hazards to provide more-detailed technical information.
Fire Hazards from Undeveloped Areas
1. The City shall support existing Fire Department programs such as the weed
abatement program which reduces risk from high fire hazard areas.
2. The City shall require the use of fire retardant roofing materials adjacent to high
fire hazard areas.
3. The City shall continue to support the Junior Fireman Program and other public
information activities of the Fire Department so as to lessen fire risk through
citizen education and awareness.
Flood Hazards
1. The City shall investigate the establishment of standards and criteria for
development in flood-prone areas which would fulfill federal requirements, yet
maintain the character of each existing Newport Beach village.
2. The City shall endeavor to restrict future development In areas of high flood
hazard until it can be shown that the risk is or can be mitigated.
3. The City shall support regional planning efforts toward the control of flood risk
from the Santa Ana. River and San Diego Creek by monitoring existing
programs and when appropriate joining In the endeavors of various jurisdictions
to lessen potential flood hazard.
4. The City shall prepare a flood plain management program for areas subject to
40
inundation from major rivers, streams, and creeks which may include:
A. The application� of Planned Community zoning to allow for
clustering of buildings and density transfer so as to permit
utilization of flood-prone sites without the necessity of building in
the flood plain.
B. Revisions to the building codes applicable to such areas
requiring strengthening of foundations and footings, and other
flood proofing measures.
5. The City shall require flood hazard studies as an integral portion of all
environmental impact reports, with detailed flood hazard mitigation measures,
for all projects in potential flood hazard areas.
41
APPENDIX
A. Modified Mercalli Scale
B. Richter Magnitude Scale
C. Prominent Earthquakes in California
D. Glossary Terms
42
Prominent wrthquakes in California, 1769 through September 1971
(Intensity.VIII and above)
Modified
Richter Mercalli
Date Region Magnitude Intensity
28 Jul 1769 LOS Angeles region . . . . . . . . . . . . . .
8 Dec 1812 southern California . . . . . . . . ... . . . . . . . . . . . . . . Vill-IX
21 Dec Ott coast of southern California . . . . . . . . . .. . . . . . . x
10 Jun 1836 San Francisco Bay . . . . . . . . . . . . . . . . . . . . . . . . Ix_x
Jun 1838 San Francisco region . . . . . . . . . . . . . . . . . . . . . . x
10 or
11 Jul 1855 Los Angeles County . . . . . . . . . . . . . . . . . . . . . . . . Vill
9 Jan 1857 Near Fort Tejon . . . . . . . . . . . . . . . . Possibly a . . X_XI
26 Nov 1858 San Jose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vill
12 Nov 1860 Humboldt Bay . . . . . . . . . . . . . . . . . . . . . . . . . . Vill
3 Jul 1861 Near Livermore . . . . . . . . . . . . . . . . . . . . . . . . . . Vill
I Oct 1865 Fort Humboldt-Euraka area . . . . . . . . . . . . . . . . . . Vill-IX
a Oct Santa Cruz Mountains . . . . . . . . . . . . . . . . . . . . . . Vill-IX
21 Oct 1868 Hayward . . . . . . . . . . . . . . . . . . . . . . . . I . . . . . Ix_x
26 Mar 1872 Near Lone Pine . . . . . . . . . . . . . . . . Possibly 8 . . X_XI
19 Apr 1892 Vacaville . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ix
21 Apr Winters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Ix
4 Apr 1893 Northwest of Los Angeles . . . . . . . . . . . . . . . . . . . . Vill.Ix
20 Jun 1897 Near Hollister . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vill
14 Apr 1898 Mendocino area . . . . . . . . . . . . . . . . . . . . . . . . . . VII:_Ix
22 Jul 1899 San Bernardino County. . . . . . . . . . . . . . . . . . . . . . Vill
25 Dec San Jacinto-Hemet area . . . . . . . . . . . . . . . . . . . . Ix
27 &
31 Jul 1902 Santa Barbara County . . . . . . . . . . . . . . . . . . . . . . Vill
is Apr 1906 San Francisco region. . . . . . . . . . . . . . . . 8.3 . . . . X1
is Apr BrawleY. imperial Vall ey . . . . . . . . . . G to 6.9 . . . . Vill
28 Oct 1909 Humboldt county . . . . . . . . . . . . . . . 6+ Vill
11 Jan 1915 Los Alamo$ . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vill
22 Jun El Con tro-Calexico-Maxic3ll area . . . . . . 6.25 . . . . Vill
21 Apr 1918 San Jacinto-Hemet area. . . . . . . . . . . . . . 6.8 . . o . ix
21 Jun 1920 Inglewood . . . o . . . . . . . . I . . . . . . . . . . . . . . . . . Vill
10 Mar 1922 Cholame Valley. . . . . . . . . . . . . . . . . . . 6.5 . . . . Ix
29 Jun 1925 Santa Barbara area . . . . . . . . . . . . . . . . 6.3 . . . . Vill-IX
22 Oct 1926 Monterey Say. . . . . . . . . . . . . . . . . . 6 to 6.9 . . : . Vill
20 Aug 1927 Humboldt Bay . . . . . . . . . . . . . . . . . . . . . . . . . . Vill
4 Nov West'of Point Arguello . . . . . . . . . . . . . . 7.5 . . . . Ix.x
25 Feb 1930 Westmorland . . . . . . . . . . . . . . . o . . 5-0 . . . . Vill
I Mar Brawley . . . . . . . . . . . . . . . . . . . . . . 4.5 . . . . Vill
6 Jun 1932 Humboldt County . . . . . . . . . . . . . . . . GA . . . . Vill
10 Mar 1933 Near Long Beach . . . . . . . . 0 . . . . . . . 6.3 . . . . Ix
7 Jun 1934 Parkflold . . . . I . . . . . . . . . . . . . . . . . 6.0 . . . . Vill
13 May 1940 imperial Valley . . . . . . . . . . . . . . . . . . 7.1 . . . . x
30 Jun 1941 Santa Barbara-Carpinteria area . . . . . . . . So9 . . . . Vill
is Mar 1946 North of Walker Pass . . . . . . . . . . . . . . 6.25 . . . . Vill
29 Jul 1950 Imperial Valley . . . . . . . . . . . . . . . . . . 5-5 . . . . Vill*
21 Jul 1952 Kern County . . . . . . . . . . . . . . . . . . . . 7.7 . . . . X1
22 Aug Bakersfield. . . . . . . . . 0 . . . . . . . . . . . . 5.8 . . . . Vill
25 Apr 1954 East of Watsonville . . . . . . . . . . . o . . 5.2!1 . . . . Vill
23 Doc Eureka . . . . . . . . . . . . . . . . . . . . . . 6.6 . . . . Vil
8 Apr 1968 Northeast San Diego County . . . . . . . . . . 6.5 . . . . Vil
IOct 1�69 Santa Rosa . . . . . . . . . . . . . . . . . . . . 5.7 . . . . VII-Vill
9 Feb 1971 San Fernando . . . . . . . . . . . . . . . 0 . . . 6.6 . . . . Vill-XI
The Richter magnitude Scale was not devised until 2931. If values appear In this column for earthquakes
which occurred prior to that date, the magnitudes were determined as follows: 1) If given to the nearest tenth, the
records of older Instruments were correlated with records of Instruments now In use;2)otherwise,historical records
of intensity were used to estimate magnitude.
California Geology
**Source : " Planner' s Guide to Seismic Safety Element" - Assoc .
of Engineering Geologists
THE MERCALLI INTENSITY SCALE
(As modified by Charles F. Richter in 1956 and rearranged)
If most of these effects then the if most of these effects then the
are observed intensity is., are observed intensity is:
Earthquake shaking not felt. But people aiuy ob. Effect on people:Difficult it)stand.Shaking noticed
serve marginal effccis (if large distance earthquakes by auto drivers.
without identifying these effects us. earthquake. I Other effects: Waves on ponds; water turbid with
caused. Among them: trees. structures. liquids. inud.Small slides and caving in along sand or gravel
bodies of water sway slowly.or doors swing slowly. I banks. Large bells ring. Furniture broken. Hanging
objects quiver.
Effect on people. Shaking felt by those -at rest, Structural effects.- Masonry D*.heavily dtanagcd� Vill
especially it'they are indoors.and by tbose tin upper 11 Masonry C* damaged, partially collapses in sonic
floors. cases; some damage to Masonry B'; none to
Masonry A*. Slucco and sonic masonry walls full.
Effect on people:Felt by most people indoors. Chimneys, factory stacks. monuments, towers.
Sonic can estimate duration of shaking. But many elevated tanks twist or fall. Frame houses moved on
may not recognize shaking or building as caused by III foundations if not bolted down; loose panel walls
an earthquake;the shaking is like that caused by the thrown out. Decayed piling broken off. J
passing (if light trucks. I
Effect on people, General fright. People thrown it)
Other effects. Hanging objects swing. ground. I
Structural effeCis: Windows or doors rattle. IV Other effects: Changes in flow or temperature of
Wooden walls and frames creak. springs and wells.Cracks in wet ground and(in steep
slopes. Steering of autos affected. Branches broken
Effect on peopleXch by everyone indoors. Many from trees.
estimate duration of shaking. But they still may not Structural effects. Masonry D*destroyed:Masonry Ix
recognize it as caused by an earthquake.The shaking C* heavily damaged. sometimes with complete
is like that caused by the passing or heavy trucks. collapse; Masonry B'is seriously damaged.General
though sometimes. instead, people may feel the sen. damage it) foundations. Frame structures. if not
sation of a jolt, as if a heavy ball had struck the V bolted, shilled off foundations. Fiannes racked.
wulls. Rcservoirs�seriously damaged. Underground pipes
Other effects: Hanging objects swing. Standing broken. J
autos rock.Crockery clusbes.dishes rattle or glasses
clink. Effect on people. General Panic.
Structural effects:Doors close,open or swing.Win. J Other effects. Conspicuous cracks in ground. In -
dows rattle. areas of soft ground. sand is ejected through holes
and pilcsup into a small crater,and,in muddyarCdS,
Effect on people: Felt by everyone indoors and by water rountains are formed. x
most people outdoors. Many now estimate not only Structural effects., Most masonry and frame struc-
the duration or shaking but also its direction and tures destroyed along with their foundations. Sonic
have no doubt as to its cause. Sleepers wakened. well-built wooden structures and bridges destroyed.
Other effects: Hanging objects swing. Shutters or Serious damage to danis, dikes and embankments.
pictures move. Pendulum clocks stop,start or change III Railroads bent slightly.
rule, Standing autos rock. Crockery clashes, dishes
rattle or glasses clink. Liquids disturbed, sonic Effect on people. General panic.
spilled. Small unstable objects displaced or upset. Other effects., Large landslides. Water thro%n (in
Structural effects. Weak plaster and Masonry D' banks of canals,rivers,lakes,etc.Sand and mud shif-
crack, Windows break. Doors close, open or swing. i ted horizontally on beaches and flat land. x/
Structural effects:General destruction of buildings.
Effect on people: Felt by ever)one. Many are Underground pipelines completely out of service.
frightened and run outdoors. People walk un- Railroads bent greatly.
steadily.
Other effects. Small church or school bells ring. Effect on people.- General panic.
Pictures thrown offwalls.knicknucks and books oil Other effects: Same as for Intensity X.
slickes. Dishes or glasses broken, Furniture moved Structural effects: Damage nearly total, the uhi- x/I
or overturned.Trees.bushes shaken visibly.or heard VII matc catastrophe.
if) rustic. Other iffects, Large rock massesdkplaced Lincsof
Structural effects. Iviasonry D* damaged: sonic sight and level distorted, Objects thrown into air.
cracks in Masonry C*.Weak chimneys break at root
line. Plaster,loose brick%.stories,tiles,cornices.on. eivia%ino) A: Gocid �orkmanship and noirt.o. -coileirced.
deiigncil to re%kt hacral himes.
braced parapets and atchitectural ornaments fall. hlawnry If: Gotid waknodadtill Jad in4stoo. ruiti6oved.
Concrctc irrigation ditches damaged. J masintry (': Good %toikinanoup and taoriar. unreinforct-d.
%la�onry D: Poor %wil,nina0up and intioar and �cak intactwk.
like adobe.
Source: "Urban Geology Master Plan for Cali �ornia Phase V
Division of Mines and Geology
RICHTER MAGNITUDE SCALE*
The Richter Magnitude Scale, named after Dr. Charles F. Richter, Professor Emeritus of
the California Institute of Technology, measures the energy of an earthquake at its source,
and is the scale most commonly used but often misunderstood. On this scale, the
earthquake's magnitude is expressed in whole numbers and decimals. However, Richter
magnitudes can be confusing and misleading unless the mathematical basis for the scale
is understood. It is important to recognize that magnitude varies logarithmically with the
wave amplitude of the quake recorded by the seismograph. Each whole number step of
magnitude on the scale represents an increase of 10 times in the measured wave
amplitude of an earthquake, and an increase of 31 times in the amount of energy released
by the quake. Thus, the amplitude of an 8.3 earthquake releases almost one million times
more energy than one of magnitude 4.3.
A quake of magnitude 2 on the Richter Scale is the smallest quake normally felt by
humans. Earthquakes with a Richter magnitude 7 or more are commonly considered to
be major. The Richter magnitude scale has no fixed maximum or minimum; observations
have placed the largest recorded earthquakes in the world at about 8.9, and the smallest
at about 3. Earthquakes with magnitudes smaller than 2 are called "micro-earthquakes".
Richter magnitudes are not used to estimate resulting earthquake damage. An
earthquake in a densely populated area, which results in many deaths and considerable
damage, may have the same magnitude as an earthquake that occurs in a barren, remote
area, that may do nothing more than frighten the wildlife.
*Source: "Los Angeles Seismic Safety Element"
45
GLOSSARY TERMS
ACCELERATION
Rate of change in velocity, felt as a force by objects. Measured here in g's , where 1.0g is
the acceleration of gravity.
AFTERSHOCKS
A sequence of smaller shocks following an earthquake.
ALLUVIUM
Geologically recent surface deposits, which have not undergone significant cementation or
consolidation. Typically sands, gravels, silts, or clays.
ANTICLINAL STRUCTURE
An elongated fold in a rock mass where the slides or limbs slope downward away from the
crest.
ASEISMIC
Earthquake resistant.
BEDROCK
The solid, undisturbed rock in place either at the surface or beneath superficial deposits of
soil.
CREEP
An imperceptibly slow, more or less continuous downward and outward movement of
slope-formihg soil or rock.
EPICENTER
The point on the earth's surface directly above the focus of an earthquake.
FAULT
A plane of breakage in rock or soil, along which significant (greater than an inch or so)
46
7
offsetting of the two sides of the plane has taken place, due to tectonic forces.
FAULT SCARP
A relatively steep, straight ground slope which is caused by the movement along a fault.
FAULT TRACE
The line of intersection of a fault surface with the earth's surface.
FAULT ZONE
Consists of numerous interlacing small faults.
GROUND BREAKAGE AND LURCHING
Surface cracking or distortion due to motions of the ground during an earthquake. Not
necessarily directly connected to a fault plane.
GROUND FAILURE
Possible effect of seismic activity on earth materials including but not limited to landsliding,
surface rupture, liquefaction, compaction, and subsidence.
GROUND SHAKING
Motions of the soil or rock during an earthquake. Nay or may not result in breakage,
lurching, or other phenomena.
GROUND WATER
That part of the subsurface water which is in the zone of saturation.
INTENSITY (MERCALLI
The degree of shaking at a specified place; rated by an experienced observer using a
descriptive scale.
LANDSLIDE
The downward and outward movement of soil, rock, or other earth materials.
LINEAR SYSTEMS, NODES,AND CORRIDORS
47
A linear system is a network of facilities and rights-of-way providing for the delivery of a
commodity or service. Examples include roadways, pipelines, electrical transmission lines
and facilities, channels, and communication networks. Such systems are characterized by
nodes which may represent an origin, terminus, or intersection of one or more rights-of-
way. Corridors have been defined as routes carrying one or more linear systems or
segment thereof.
LIQUEFACTION
The sudden loss of strength of soils under saturated conditions due to earthquake shock.
LURCHING
Sudden motion at ground surface due to acceleration of the subsoil from earthquake
shock.
MAXIMUM POSSIBLE EARTHQUAKE
The largest earthquake which the geologist estimates could ever occur on the given fault.
The probability of such an earthquake occurring is considered to be extremely remote.
MAXIMUM CREDIBLE EARTHQUAKE
The largest earthquake which the geologist estimates may occur within the life of the
proposed structures (50 - 100 years—) on the given fault. The probability of such an
earthquake 15 considered to be low, but is definitely within the realm of possibility.
MAXIMUM PROBABLE EARTHQUAKE
The largest earthquake which the geologist estimates is likely to occur on the given fault
within the life of the structure (50- 100 years).
MUD FLOW
The downward and outward movement of soil and rock or other earth materials in a plastic
or near liquid state.
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OFFSET
The horizontal and/or vertical distance between two parts of a faulted bed previously
joined.
PLEISTOCENE
The next-to-the-last epoch of geologic time; corresponding with the last ice age; its
duration was only about 3 million years.
POSSIBLE GROUND RUPTURE ZONE
For the present study, any mapped fault or historic breakage longer than 1/2 mile in length,
with the zone 1/8 mile wide in rock and 112 mile in soil.
QUATERNARY
The second of the two Cenozoic time periods; encompassed both the Pleistocene and
Holocene epochs.
REVERSE FAULT
A steeply inclined fault, on which motion is primarily in a vertical sense, with the "over
hanging" side moving upward.
(RICHTER) MAGNITUDE
A measure of the energy released by an,earthquake at its source.
RIGHT OR LEFT LATERAL FAULT
A fault on which relative motion is primarily in a horizontal sense, with the motion of the
opposite side of the fault, when viewed from one side, to either the right or left,
respectively.
ROCK FALL
The vertical movement of rock.
SEICHE
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The oscillation or sloshing of water in a lake, bay, or other enclosed body of water caused
by seismic activity, or landsliding.
SEISMICITY
A general term, relating to the general level of earthquake activity in an area.
SLOPE STABILI
The ability of a slope of soil or rock materials to resist moving downhill.
STRATIGRAPH
Deals with the formation, composition, sequence, and correlation of the stratified rocks as
part of the earth's crust.
SUBSIDIARY FAULTS
Auxiliary cracks either branching obliquely or lying subparallel to the main line of rupture.
SUBSIDENCE
A local mass movement of earth material in which surface material is displaced vertically
downward as an aereal settlement with little or no horizontal component.
SURFACE RUPTURE
Ground breakage at the surface caused by faulting.
TECTONIC
Designating or pertaining to changes in the structure of the earth's crust, the forces
responsible for such deformations, or the external forms produced.
THRUST FAULT
A fault that has a low angle of inclination with reference to a horizontal plane.
TSUNAMI
A sea wave generated by a submarine earthquake, landslide, or volcanic activity.
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