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Enhanced Geothermal Systems and Calpine/Unocal Geysers Networks

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EGS at The Geysers

Gap in BG (Geysers) data July 8-9, 2017

In 2009 the US Department of Energy (USDOE) Geothermal Technologies Program began an Enhanced Geothermal Systems (EGS) project to investigate the process of enhancing high temperature geologic formations to provide commercial scale electric power generation. As part of this effort, demonstration projects were initiated that were jointly funded by industry and DOE. One of the main components of the demonstration projects is to record local seismicity before during and after the injection of water into the hot rocks to provide information that may indicate the creation of permeable fractures as well provide information on the generation of any induced seismicity. Lawrence Berkeley National Labs Earth Sciences Division was funded to perform this EGS earthquake monitoring. The NCEDC is archiving both event and waveform data that is being generated from each of the DOE demonstration sites data and providing it to the public.

Current EGS sites include projects at The Geysers, California, including the NW Geysers EGS project.

Network Code

Station information
LBL EGS Geysers website

Data Access

Calpine/Unocal Geysers Seismic Network

The Calpine Geysers seismic network, consisting of up to 49 different borehole monitoring sites, was initially deployed and operated by the Unocal Geothermal Division on behalf of the geothermal energy producers in the California Geysers geothermal field. In 1999, the Unocal geothermal fields at the Geysers were acquired by the Calpine Corporation. Calpine has continued Unocal's collaboration with the NCEDC and has made data available for public distribution.

The Calpine/Unocal Geysers dataset is a collection of digial microearthquake seismograms recorded by this network. Over 10 years of digital microearthquake seismograms (1989 through 2000) have been released for archiving and distribution through the NCEDC.

Calpine has also released an unedited earthquake catalog for events in 1995-1998 with approximate times and very rough hypocenters for some of the event represented in the time series, primarily as an index aid for the waveforms. Calpine makes no claims that this catalog is complete in any manner, and assumes no responsibilty for the accuracy or usefulness of the catalog data.

Network Code

Station information
The Geysers network has evolved over time, with different station configurations and different recording systems. In 1989, the w array covered the northeastern part of the field and was operated for about a year, using a Sprengnether processer called QLog. In late 1989, the station coverage was expanded fieldwide and the QLog was replaced with an Owl processor (g array), with some overlap between the two systems. In 1992, the Owl processer was replaced with an IASPEI system (f array).

The Geysers sensors are deployed in a combination of surface and borehole installations. The borehole stations are SB4B, SQK, DXR, STY, FUM, FNF, TCH, and DVB. The sensors are HS-1, with data digitized at 100 sps.

The orientation of the surface sensors is denoted by the channel name - e.g. ***N and ***E. The borehole sensors are not oriented and are typically named ***X and ***Y.

Data Access
The 1989-2000 microearthquake waveform data are available in its native PCQL format as an assembled dataset at the NCEDC.

  • w array - 1989.001 through 1989.365.
  • g array - 1989.279 through 1992.218.
  • f array - 1992.218 through 2000.366.

Several program exist to convert the data to AH or MiniSEED format:

  • pcql2ah - convert PCQL data to Lamont AH xdr format.
  • pcql2ms - convert PCQL data to MiniSEED Steim1 format.

The unedited earthquake catalog for events is available: