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SEISMIC
EVENTS AT THE GEYSERS
For further information about
recent earthquakes at The Geysers, their relationship to
geothermal drilling, and to see an exciting interactive map monitoring
real-time seismic activity at The Geysers, please check out the link
at: http://www.altarockenergy.com/ and
click on "Demo Project".
To view a
map of recent local earthquakes, please check out the USGS Site:
Recent
Earthquakes of the S.F. Bay Region
A review of Santa Rosa Injection and Seismicity
(August 2004)
The Santa Rosa-Geysers
Recharge Project (SRGRP) began piping tertiary-treated reclaimed water up to Calpine's
Geysers steamfields in significant quantities in November 2003. So far
the project looks like a success. The system has been operating reliably
and we're already seeing evidence of some benefits in certain areas. As
of the end of August, 2004, the system had delivered over 3 billion gallons
of SRGRP reclaimed water, all of it distributed via Calpine's new pipeline
system into 11 injection wells. Compared to the average injected for the
same period (November through August) during the previous six seasons,
injection is up by about 36% (see table). On the other hand, total injection
with SRGRP on line was not much higher than previously achieved during
the winter of 1997 - 98, when unusually wet weather provided an abundance
of freshwater and plant condensate for injection.
Fieldwide seismic activity has also been similar to that of the 1997 - 98 season. In general, the seismic response to the SRGRP injection has been much as predicted in the Environmental Impact Report: more microearthquakes, but little change in the number of larger quakes. The table below shows that seismic activity of magnitudes 1.5 and above has increased by 34% since SRGRP has been operating, compared to the average for the same period during the previous six years. The vast majority of these microearthquakes are too small and/or distant to be felt by people. On the other hand, earthquakes of magnitudes 3.0 and greater have been virtually unchanged since SRGRP started up, compared with the previous six-season average. The 2003 - 04 total of 13 earthquakes in this magnitude range was equaled or exceeded in three of the six pre-SRGRP seasons.
Overall, in terms of both injection and seismicity, the SRGRP is performing as expected, and Calpine looks forward to many years of future success in this partnership with the City of Santa Rosa. - Mitch Stark, Calpine Corporation
| Season |
Total Injected
(million gallons)
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Earthquake Count, M>=1.5* |
Earthquake Count M>=3.0* |
| Nov 1997 -- Aug 1998 |
8692 |
779 |
14 |
| Nov 1998 -- Aug 1999 |
7286 |
601 |
13 |
| Nov 1999 -- Aug 2000 |
6404 |
558 |
12 |
| Nov 2000 -- Aug 2001 |
5484 |
545 |
11 |
| Nov 2001 -- Aug 2002 |
6096 |
595 |
15 |
| Nov 2002 -- Aug 2003 |
6292 |
595 |
12 |
| Nov 2003 -- Aug 2004 (SRGRP operating) |
9106 |
820 |
13 |
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| Average pre-SRGRP |
6709 |
612 |
12.8 |
| Change during SRGRP operation |
36% |
34% |
1% |
* Data Source: USGS Northern California Seismic Network
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