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Many contributions in a variety of forms have greatly helped in the development,
implementation, and use of ShakeMap. ShakeMap is one important end-product of a very
sophisticated seismic network. It can only be produced within the context of a robust, real-time
seismic operation. Credit is given to all involved with the regional and national networks in the
Much of the early conceptual development of ShakeMap benefited greatly from discussions with
Professors Kanamori and Heaton at Caltech. Both the TriNet Steering and Advisory Committees
also provided ongoing oversight and feedback in the early years of TriNet. Discussions with
many colleagues, including W. Savage, K. Campbell, R. Nigbor, and M. Petersen, provided
additional guidance. Early trips to the Japanese Meteorological Agency (JMA), and in particular
discussions with Keiji Doi, were very helpful.
In implementation, Doug Given (USGS) and Phil Maechling and Egill Hauksson (Caltech) were
instrumental on the network side of the operation. Engineering-strong-motion and technical
advice as well as perspectives from Tony Shakal of the CGS is greatly appreciated. Craig
Scrivner, then at the California Department of Mines and Geology (CDMG), contributed greatly
to the initial ShakeMap software development.
At regional network centers, Kris Pankow (University of Utah), Steve Malone (University of
Washington), Kuo-wan Lin (CGS), Dan McNamara (USGS, Golden), Douglas Dreger, Peter
Lombard, and Lind Gee (U.C. Berkeley), Glenn Biasi (University of Nevada, Reno), and
Howard Bundock, David Oppenheimer, and Jack Boatwright (USGS, Menlo Park) all played a
critical role in system testing, providing feedback, and improving the ShakeMap software. In
addition, a number of other people assisted the above colleagues in the regional ShakeMap
implementation and operation. Ned Field at the USGS in Pasadena has been very helpful in
software calibration and validation and overall advice.
ShakeMap Web pages survived substantial traffic spikes due to the ingenuity and vigilance of
Stan Schwarz (USGS, Pasadena). Aesthetic improvements and integration of the ShakeMap
Web pages into the USGS Earthquake Hazards Team Web Page standard templates were guided
by Lisa Wald (USGS, Golden).
In interfacing with HAZUS with we wish to thank Douglas Huls, Dave Kehrlein, and Lisa
Christiansen of the California Office of Emergency Services, Jawhar Bouabid at Durham
Technology, and Charles Kircher of Charlie Kircher Assoc. Phil Naecker, Steve Cain, and
David Burke of Gatekeeper Systems, Inc., have been enthusiastic and supportive in their
development of ShakeCast.
We received extremely important feedback regarding the user interface from participants through
a number of meetings and workshops in California for scientific and engineering perspectives, as
well as for a very wide variety of users’ perspectives. These workshops were usually organized
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by James Goltz and Margaret Vinci. In addition, ongoing feedback has always been abundant
and provides critical advice and ideas that seeds ongoing, iterative improvements to the
The manual organization, layout, and document templates were greatly improved by Alicia
Hotovec, a summer intern from the Colorado School of Mines. Reviews by Peter Lombard and
E.V. Leyendecker improved this manual substantially.
Most of all, we are also extremely grateful for the recognition of the importance of ShakeMap
and the ongoing internal and external support for its development at all levels within the U.S.
Geological Survey. The support of John Filson, David Applegate, William Leith, Jill McCarthy,
Harley Benz, and Woody Savage has been critical.
ANSS ShakeMap Coordinators
U.S. Geological Survey, Golden, Colorado, email@example.com
U.S. Geological Survey, Pasadena. firstname.lastname@example.org
Vincent Quitoriano, U.S. Geological Survey, Pasadena, email@example.com
U.S. Geological Survey, Menlo Park, firstname.lastname@example.org
ShakeMap Regional Coordinators
Bruce Worden, email@example.com
David Oppenheimer, firstname.lastname@example.org
John Boatwright, email@example.com
Howard Bundock, firstname.lastname@example.org
Kris Pankow, email@example.com
Thomas Murray, firstname.lastname@example.org
Vincent Quitoriano, email@example.com
Steve Malone, firstname.lastname@example.org
Glenn Biasi, email@example.com
Mitch Withers, firstname.lastname@example.org
Won-Young Kim, email@example.com
Christa Von Hillenbrandt, firstname.lastname@example.org
James Goltz, California Governor’s Office of Emergency Services, Pasadena.
Margret Vinci, California Institute of Technology, Pasadena.
Lisa Wald, United States Geological Survey, Golden.
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1 USERS’ GUIDE
ShakeMap originated primarily as an Internet-based system for real-time display. Although the
color-coded intensity maps on the Web site are the most visible result of ShakeMap system and
constitute the most commonly accessed and downloaded product, they are just one representation
of the ShakeMap output. ShakeMap produces grids of acceleration and velocity amplitudes,
spectral response values, instrumental intensities, GIS files, and a host of other products for
In this guide, we describe the basic ShakeMap products and their current and potential uses.
First, we provide an overview of the current ShakeMap applications. We then explain the
different formats and types of maps available and describe the ShakeMap Web pages. Next, we
expand on different automated mechanisms to receive ShakeMap, including new approaches
under development, particularly ShakeCast. We also describe Scenario Earthquake ShakeMaps,
which provide the basis for pre-earthquake planning and understanding the potential effects of
large earthquakes in the future. In each subsection, we try to provide concrete examples of
potential uses of each product as well as notable users for each example.
Until recently, the most common information available immediately following a significant
earthquake was its magnitude and epicenter. However, the damage pattern is not a simple
function of these two parameters alone, and more detailed information must be provided to
properly ascertain the situation. For example, for the magnitude-6.7 February 9, 1971,
earthquake, the northern San Fernando Valley, California, was the region with the most damage,
even though it was more than 15 km from the epicenter. Likewise, areas strongly affected by the
1989 Loma Prieta and 1994 Northridge, California, earthquakes (magnitudes 6.9 and 6.7,
respectively) that were either distant from the epicentral region or out of the immediate media
limelight were not fully appreciated until long after the initial reports of damage. The full extent
of damage from the magnitude-6.9 1995 Kobe, Japan, earthquake was not recognized by the
central government in Tokyo until many hours later (e.g., Yamakawa, 1997), seriously delaying
rescue and recovery efforts.
A ShakeMap is a representation of ground shaking produced by an earthquake. The information
it presents is different from the earthquake magnitude and epicenter that are released after an
earthquake because ShakeMap focuses on the ground-shaking produced by the earthquake, rather
than the parameters describing the earthquake source. So, although an earthquake has one
magnitude and one epicenter, it produces a range of ground shaking levels at sites throughout the
region depending on distance from the earthquake, the rock and soil conditions at sites, and
variations in the propagation of seismic waves from the earthquake due to complexities in the
structure of the Earth's crust.
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Part of the strategy for generating rapid-response ground-motion maps was to determine the best
format for reliable presentation of the maps given the diverse audience, which includes scientists,
businesses, emergency response agencies, media, and the general public. In an effort to simplify
and maximize the flow of information to the public, we have developed a means of generating
not only peak ground acceleration and velocity maps, but also an instrumentally derived,
estimated Modified Mercalli Intensity map. This Instrumental Intensity map makes it easier to
relate the recorded ground-motions to the expected felt and damage distribution. We have also
further simplified the presentation of the Instrumental Intensity ShakeMap specifically for the
resolution and audience of broadcast television to reach the widest audience possible. At the
same time, we preserve a full range of utilities of recorded ground-motion data by producing
maps of response spectral acceleration, which is not particularly useful to the general public, but
which provides fundamental data for loss estimation and engineering assessments.
Although we show several ShakeMap Web page examples in the following documentation, this
guide is no substitute for the ShakeMap Web pages, and we recommend having a browser open
to those pages while this guide is in hand.
1.2 Current Applications of ShakeMap
Prior to fully describing the array of ShakeMap products and formats, we briefly expand on the
most common applications of ShakeMap.
1.2.1 Emergency Response and Loss Estimation
The distribution of shaking in a large earthquake, whether expressed as peak acceleration or
intensity, provides responding organizations a significant increment of information beyond
magnitude and epicenter. Real-time ground-shaking maps provide an immediate opportunity to
assess the scope of an event, that is, to determine what areas were subject to the highest
intensities and probable impacts as well as those that received only weak motions and are likely
to be undamaged. These maps will certainly find additional utility in supporting decision-
making regarding mobilization of resources, mutual aid, damage assessment, and aid to victims
For example, the Hector Mine earthquake of October 16, 1999, provides an important lesson in
the use of ShakeMap to assess the scope of the event and to determine the level of mobilization
necessary. This earthquake produced ground-motion that was widely felt in the Los Angeles
basin and, at least in the immediate aftermath, required an assessment of potential impacts. It
was rapidly apparent, based on ShakeMap, that the Hector Mine earthquake was not a disaster
and despite an extensive area of strong ground shaking, only a few small desert settlements were
affected. Thus, mobilization of a response effort was limited to a small number of companies
with infrastructure in the region and brief activations of emergency operations centers in San
Bernardino and Riverside Counties and the California Office of Emergency Services (OES),
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Quote from a member of a Caltrans County bridge crew, following the 1999 Hector Mine
“I just wanted to say “Thank you” for having your web site made available to everyone
on the Internet. As a member of the Caltrans Bridge crew here in San Bernardino
county, information on the recent quakes such as the 7.1 we had last weekend was found
right here at your site within a few minutes of signing on… I can’t tell you how much time
and money was saved knowing where to look [for damage] by having this site at our
fingertips. Great Work.”
Unnecessary response in an effort to fully assess the potential effects of an earthquake, although
not as costly as inadequate or misguided response in a real disaster, can be costly as well. Had a
magnitude-7 earthquake occurred in urban Los Angeles or another urban area in California,
ShakeMap could have been employed to quickly identify the communities and jurisdictions
requiring immediate response. To help facilitate the use of ShakeMap in emergency-response,
ShakeMap is now provided to organizations with critical emergency response functions
automatically through the Internet with electronic “push” technology (see Section 1.5). These
organizations and utilities include the State of California OES, the Los Angeles County Office of
Emergency Management, Southern California Edison, and the Los Angeles Metropolitan Water
ShakeMap ground-motion maps are also customized and formatted into Geographic Information
Systems (GIS) shapefiles for direct input into the FEMA’s U.S. (HAZUS) loss estimation
software. These maps are rapidly and automatically distributed to the California OES for
computing HAZUS loss estimates and for coordinating State and Federal response efforts. This
is a major improvement in loss-estimation accuracy because actual ground-motion observations
are used directly to assess damage rather than relying on simpler estimates based on epicenter
and magnitude alone, as was customary.
A ShakeMap-driven calculation of estimated regional losses can provide focus to the
mobilization of resources and expedite the local, State, and Federal disaster declaration process,
thus initiating the response and recovery machinery of Government. ShakeMap, when overlaid
with inventories of critical facilities (e.g., hospitals, police and fire stations, etc.), highways and
bridges, and vulnerable structures, provides an important means of prioritizing response. Such
response activities include: shelter and mass care, search and rescue, medical emergency
services, damage and safety assessment, utility and lifeline restoration, and emergency public
In addition to GIS-formatted maps specifically design for HAZUS, we also make shapefiles for
more general GIS use. These layers are fundamental as base maps upon which one can overlay a
user’s infrastructure or inventory. For example, ShakeMaps are also being distributed to
regional and State utility providers to enable them to determine areas of their networks that may
have sustained damage. Using GIS systems, quick analysis of the situation is possible, and
decision-making is greatly facilitated. Insurance, engineering, financial institutions, and others
now routinely use these GIS maps for both recent and past earthquakes.
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1.2.2 Public Information and Education
The rapid availability of ShakeMap on the Internet combined with the urgent desire for
information following a significant earthquake makes this mapping tool a source of emergency
public information and education. In instances in which an earthquake receives significant news
coverage, the ShakeMap site as well as the Community Internet Intensity Map
(which poses the
question, “Did you feel it?”) receives an enormous increase in Website visitors.
On October 16, 1999, local television stations devoted considerable airtime to the Hector Mine
earthquake. During live news briefings, Caltech and USGS scientists employed ShakeMap to
discuss the event, invited viewers to visit the ShakeMap Website and posted the Web address
prominently above the podium in the media center. By the end of the day, the ShakeMap
Website had received more than 300,000 visitors. Even for small events, rapid and reliable
earthquake information is important. For instance, on January 13, 2001, when two magnitude-4
events, centered in the northeast San Fernando Valley area of Los Angeles, were followed by
local news coverage, Web visits peaked at 233 hits per second.
Acknowledging the importance of ShakeMap as a tool for public information and education, we
developed a “TV” ShakeMap in cooperation with regional news organizations. This version of
ShakeMap represents a substantial simplification of the “official” map that appears on the
ShakeMap Website. Based on recommendations of news representatives, acceleration and
velocity were omitted from the TV version of ShakeMap. Concern that magnitude and intensity
might be confused prompted removal of Roman numerals representing intensity, and intensity
was depicted using only the color bar. Magnitude and location were enlarged and posted at the
top of the map.
The ShakeMap for television audiences was developed specifically to encourage broadcast
journalists to provide a more accurate depiction of earthquakes in news reports. Prior to
ShakeMap, the typical visual representation of an earthquake consisted of a map overlay with the
epicenter and radiating concentric rings to represent ground-motion. The patterns of ground-
motion are not symmetrical as suggested by these illustrations, and the use of these
oversimplified depictions represents an underutilization of available technology by the news
media. Use of ShakeMap to discuss an earthquake that has just occurred not only provides a
more accurate image of earthquake ground-motion patterns, it also provides important additional
information regarding the potential severity of shaking that is useful both to residents of the area
impacted and those outside the area who are concerned about friends and family.
ShakeMaps are now reaching a much wider audience through television broadcasting than would
be possible through the Internet alone. As an example, a recent magnitude-4.2 earthquake near
Valencia on January 28, 2002, which was felt throughout the San Fernando Valley and northern
Los Angeles basin, occurred at 9:54 p.m. At least one local news organization lead the 10
Invites Web visitors (http://earthquake.usgs.gov/shake under “Did You Feel It?”) to record their
observations on a questionnaire. The data obtained are aggregated to establish a zip-code-based
intensity profile for the event (See Wald and others, 1999c, for more details).
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o’clock News with a ShakeMap image providing information about the distribution of shaking to
millions of viewers only 6 minutes after the shaking.
1.2.3 Earthquake Engineering and Seismological Research
For potentially damaging earthquakes, ShakeMap also produces response spectral acceleration
values at three periods (0.3,1.0, and 3 s) for use not only in loss estimation, as mentioned earlier,
but also for earthquake engineering analyses. Response spectra for a given location are useful
for portraying the potential effects of shaking on particular types of buildings and structures.
Following a damaging earthquake, ShakeMaps of spectral response will be key for prioritizing
and focusing post-earthquake occupancy and damage inspection by civil engineers.
In addition to providing information on recent events, ShakeMap Web pages provide maps of
shaking and ground-motion parameters for past significant earthquakes. Engineers have found
these maps helpful in evaluating the maximum and cumulative effects of seismic loading for the
life of any particular structure. This is particularly relevant given the recent discovery of the
potential damage to column/beam welds in steel buildings following the 1994 Northridge
In seismological research, ShakeMap has been proven particularly effective in gaining a quick
overview of the effects of geological structure and earthquake rupture processes on the nature of
recorded ground-motions. ShakeMaps showing the distribution of recorded peak ground
acceleration (PGA) and peak ground velocity (PGV) overlain on regional topography maps allow
scientists to gauge the effects of local site amplification because topography is a simple proxy for
rock versus deep-basin soil-site conditions. This can lead to more detailed investigations into the
nature of the controlling factors in generating localized regions of damaging ground-motions.
1.2.4 Planning and Training: ShakeMap Earthquake Scenarios
In planning and coordinating emergency response, utilities, local government, and other
organizations are best served by conducting training exercises based on realistic earthquake
situations—ones that they are most likely to face. Scenario earthquakes can fill this role. The
ShakeMap system can be used to map ground-motion estimates for earthquake scenarios as well
as real data. Scenario maps can be used to examine exposure of structures, lifelines, utilities, and
transportation conduits to specific potential earthquakes. ShakeMap automatically includes local
effects due to site conditions. The ShakeMap Web pages now have a special section under the
Archives pages that display selected earthquake scenarios. Additional scenario events will be
supplied as they are requested and generated. To contact the ShakeMap Working Group, please
use the comment form available on the Web site. The USGS is also planning to make a
concerted effort to provide scenario earthquakes online for all regions of the United States.
The U.S. Geological Survey has evaluated the probabilistic hazard from active faults in the
United States for the National Seismic Hazard Mapping Project. From these maps it is possible
to prioritize the best scenario earthquakes to be used in planning exercises by considering the
most likely candidate earthquake fault first, followed by the next likely, and so on. Such an
analysis is easily accomplished by hazard disaggregation, in which the contributions of
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individual earthquakes to the total seismic hazard, their probability of occurrence, and the
severity of the ground-motions are ranked. Using the individual components ("disaggregations")
of these hazard maps, a user can properly select the appropriate scenarios given their location,
regional extent, and specific planning requirements.
Given a selected event, we have developed tools to make it relatively easy to generate a
ShakeMap earthquake scenario. First we need to assume a particular fault or fault segment will
(or did) rupture over a certain length or segment. We then determine the magnitude of the
earthquake based on assumed rupture dimensions. Next, we estimate the ground shaking at all
locations in the chosen area around the fault, and then represent these motions visually by
producing ShakeMaps. The scenario earthquake ground-motion maps are identical to those made
for real earthquakes—with one exception: ShakeMap scenarios are labeled with the word
“SCENARIO” prominently displayed to avoid potential confusion with real earthquake
At present, ground-motions are estimated using empirical attenuation relationships. We then
correct the amplitude at that location based on the local site soil (NEHRP, see Borcherdt, 1994)
conditions as we do in the general ShakeMap interpolation scheme. Finiteness is included
explicitly, but directivity enters only through the empirical relations. Depending on the level of
complexity needed for the scenario, event-specific factors such as directivity and variable slip
distribution could also be incorporated in the amplitude estimates fed to ShakeMap. Scenarios
are of fundamental interest to scientific audiences interested in the nature of the ground shaking
likely experienced in past earthquakes as well as the possible effects due to rupture on known
faults in the future. In addition, more detailed and careful analysis of the ground-motion time
histories (seismograms) produced by such scenario earthquakes is highly beneficial for
earthquake-engineering considerations. Engineers require site-specific ground-motions for
detailed structural response analysis of existing structures and future structures designed around
specified performance levels. In the near future, we hope these scenarios will also provide
synthetic time histories of strong ground-motions that include rupture-directivity effects.
Our ShakeMap earthquake scenarios are an integral part of emergency-response planning.
Primary users include city, county, State and Federal Government agencies (e.g., the California
Office of Emergency Services, FEMA), and emergency-response planners and managers for
utilities, businesses, and other large organizations. Scenarios are particularly useful in planning
and exercises when combined with loss-estimation systems such as HAZUS and the Early Post-
Earthquake Damage Assessment Tool (EPEDAT), which provide scenario-based estimates of
social and economic impacts.
1.3 Maps and Data Products
ShakeMap is fundamentally a geographic product: the spatial representation of the potentially
very complex shaking associated with an earthquake. By its complicated nature, we are required
to generate numerous maps that portray various aspects of the shaking that are customized for
specific uses or audiences. For some uses, it is not the maps but the components that make up
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the ShakeMaps that are of interest in order to recreate or further customize the maps. In this
section we further describe these ShakeMap component products and the variety of maps and
formats. Interactive and automatic access to these products is described in sections 2.4.8 and 2.5,
For each earthquake that warrants generating a ShakeMap, all maps and associated products for
that event are available on the earthquake-specific Web pages as described below.
1.3.1 Interpolated Grid File
As described in the Technical Manual, the fundamental output product of the ShakeMap
processing system is a finely sampled grid of latitude and longitude pairs with associated
amplitude values of shaking parameters at each point. These amplitude values are derived by
interpolation of a combination of the recorded ground shaking observation and estimated
amplitudes at locations that fill in gaps, with consideration of site amplification at all interpolated
points. The resulting grid (hereafter, grid.xyz) of amplitude values provides the basis for
generating color-coded intensity contour maps, for further interpolation to infer shaking at
selected locations, and for generating GIS-formatted files for further analyses.
The grid.xyz file is an ASCII file contains values that contains X, Y, Z (degrees longitude,
degrees latitude, and amplitude, respectively) values of the peak amplitudes at the ShakeMap
map grid nodes in the following format:
The first line is a header with:
<name/event_ID of event> <mag> <epicentral lat> <epicentral lon> <MMM
DD YYYY> <HH:MM:SS timezone> <W bound> <S bound> <E bound> <N bound>
(Process time: <time>) <Location String>
The first 'time' field is the time of the event. 'Process time' is the time this file was last updated.
Below is an example of the header for the 1994 Northridge earthquake ShakeMap:
Northridge 6.7 34.213 -118.5357 JAN 17 1994 04:30:55 PST -119.1857
33.7775 -117.857 34.6485 (Process Time: Wed Nov 4 17:25:18 1998)
For large or historic earthquakes the "Location String" will usually be the name of the
earthquake, otherwise it will be something of the form "12.1 mi. SSW of Carpinteria, CA."
The remaining lines are of the form:
<lon> <lat> <pga> <pgv> <ii> <sa03> <sa10> <sa30>
where <lon.> is longitude in degrees, <lat> is latitude in degrees, <pga> is peak ground
acceleration (PGA) in units of %g, <pgv> is peak ground velocity (PGV) in units of cm/s, <ii> is
Instrumental Intensity in decimal intensity values, and <sa> is spectral acceleration in units of
%g. Spectral accelerations are provided for periods of 0.3, 1.0, and 3 s, all with 5 percent
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damping. These are the commonly used and requested periods, and they are fairly standard for a
number of loss-estimation algorithms (e.g., HAZUS).
If the grid file name ends with '.zip,' the file has been compressed with the Zip utility and will
need to be unzipped before it can be used. The compressed version of the ASCII grid is now our
1.3.2 Grid File Metadata
Because the grid is the fundamental derived product from the ShakeMap processing, it is fully
described in an accompanying metadata file following Federal Geographic Data Committee
(FGDC) standards for geospatial information. We do not generate metadata for the parametric
data, because that is archived by the regional seismic networks. In fact, because all other
ShakeMap products are derived from the gird file, it is sufficient to fully characterize only the
grid file using the metadata standards.
This metadata file is distributed via the event-specific Web pages for each earthquake on the
The metadata are provided in text, HTML, and XML formats.
1.3.3 GIS Products
ShakeMap processing does not occur in a Geographic Information System (GIS), but we post-
process the grid file (above) into shapefiles for direct import into GIS. Shapefiles are comprised
of three standard associated GIS files:
.dbf = A DBase file with layer attributes
.shp = The file with geographic coordinates
.shx = An index file
In this application, the shapefiles are contour polygons of the peak ground-motion amplitudes in
ArcView shapefiles. These contour polygons are actually equal-valued donut-like polygons that
sample the contour map at fine enough intervals to accurately represent the surface function. We
generate the shapefiles independent of a GIS using a shareware package (shapelib.c), which
employs a 4-point method for contouring.
There is an archive of files (three files for each of the mapped parameters) compressed in Zip
22.214.171.124 HAZUS’99 Shapefiles and HAZUS-MH Geodatabases
We generate shapefiles that are designed with intervals that are appropriate for use with the
Federal Emergency Management Agency’s (FEMA) HAZUS software, though they may be
imported into any GIS package that can read ArcView shapefiles. Because HAZUS software
requires peak ground velocity (PGV) in inches/s, this file may not be suitable for all applications.
The contour intervals are 0.04G for PGA and the two spectral acceleration parameters (HAZUS
only uses the 0.3 and 1. s periods), and 4 inches/s for PGV.
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