How one utility uses earthquake data for earthquake mitigation and rapid emergency response
Marcia K. McLaren
Pacific Gas and Electric Company Geosciences Department
245 Market Street, Room 420, Mail Code N4C San Francisco, CA 94105
Abstract
The Pacific Gas and Electric Company takes a proactive role in preparing for and
responding to California earthquakes. This role includes (1) the development of a GIS
application that allows viewing, via the PG&E intranet, of earthquake data and PG&E
facilities within moments after an earthquake and (2) installing over 50 strong motion
instruments in critical buildings and substations within the greater San Francisco Bay
Area and critical hydro dams. Earthquake data from the U. S. Geological Survey
(locations, magnitudes, and ShakeMaps) are “pushed” to PG&E. Strong motion data
from PG&E instruments are compared to the initial ShakeMaps, and added to subsequent
ShakeMap revisions. By utilizing data products from the USGS, in addition to our own
data, we are able to more effectively direct our emergency response efforts, assess
damage, and restore gas and power to customers.
Introduction
The Pacific Gas and Eletric Company is proactive in its approach to preparing for and
responding to California earthquakes. Using web-based GIS technology via the PG&E
Intranet we have vastly improved our ability to disseminate earthquake information
quickly and easily within PG&E. In this paper I describe 1.) our web-based tool, why we
need this technology, how it works, and how we use it, and 2.) the PG&E Strong Motion
Instrument Program, which was implemented for site specific damage assessment at
critical PG&E facilities and to provide data to the U. S. Geological Survey’s (USGS)
regional ShakeMaps.
Web-Based GIS Application
PG&E’s service territory covers nearly 2/3 of the state of California and includes several
significant seismic sources, the largest being the San Andreas fault system. When an
earthquake occurs we not only need to know where it occurred and how big it was, but
more importantly, how close was it to a PG&E facility? We need to be able to assess
potential damage or impact to our facilities and disseminate that information quickly to
those that need to know.
Since 1996 the USGS has been posting current (the last 7 days) California earthquake
data on their website (
http://quake.wr.usgs.gov). These data include earthquake
locations, magnitudes, and more recently, ground motion estimates from ShakeMaps.
The earthquake locations are displayed on maps, with symbols sized by magnitude and
color-coded by last hour, last day, and last week. ShakeMaps are displayed on a separate
map. The earthquake locations generally are available within minutes after an event;
ShakeMaps are available within about 10 minutes. ShakeMaps are generated for
California earthquakes of magnitude 3.5 and greater.
PG&E has been using ESRI products for GIS since 1993 to maintain geocoded databases
of their facilities (e.g. service centers, pipelines, substations, power plants and
transmission lines). However, following an earthquake it was not easy to integrate the
USGS earthquake information with our facility information for rapid decision making.
Furthermore, we wanted to be able to display everything on one map. A solution to our
problem presented itself in 1999 when we discovered the web-based GIS software tool
called MapGuide, by Autodesk. Our application of MapGuide is nicknamed the
MapServer. The software resides on a server and links to several PG&E databases (e. g.
hydro dams, substations, gas lines) using the Intranet. The USGS “pushes“ earthquake
data to PG&E using UDP packets through a secure port via the Internet. The earthquake
data and PG&E facilities are available on the MapServer as layers. The earthquake
locations are shown similar to the USGS web site, with symbols scaled to magnitude and
color coded according to time. ShakeMaps are also imported and shown as a separate
layer. We are currently downloading the ShakeMap files via the USGS website,
however, in the near future we will have them automatically “pushed” to us via FTP.
