1998 - 1999

In December 1998, the original HRSN acquisition system was replaced by 10 stand-alone PASSCAL RefTek systems with continuous recording. To process these data, development of a major data handling procedure will be required in order to identify the microearthquakes down to M = -1, since continuous telemetry to the Berkeley Seismological Laboratory (BSL) and application of a central site detection scheme was not an option at that time.

In July 1999, the network was reduced to four RefTeks at critical sites that would ensure continuity in monitoring at low magnitudes and the archive of characteristic events for studying the evolution of their recurrence intervals. Properties of the 10 original sites are summarized in Table 6.2.


Table 6.1: Stations of the Parkfield HRSN. Each HRSN station is listed with its station code, network id, location, date of initial operation, and site description. The latitude and longitude (in degrees) are given in the WGS84 reference frame, the surface elevation (in meters) is relative to mean sea level, and the depth to the sensor (in meters) below the surface. Coordinates and station names for the 3 new SAFOD sites are given at the bottom.
Site Net Latitude Longitude Surf. (m) Depth (m) Date Location
EADB BP 35.89525 -120.42286 466 245 01/1988 - Eade Ranch
FROB BP 35.91078 -120.48722 509 284 01/1988 - Froelich Ranch
GHIB BP 35.83236 -120.34774 400 63 01/1988 - Gold Hill
JCNB BP 35.93911 -120.43083 527 224 01/1988 - Joaquin Canyon North
JCSB BP 35.92120 -120.43408 455 155 01/1988 - Joaquin Canyon South
MMNB BP 35.95654 -120.49586 698 221 01/1988 - Middle Mountain
RMNB BP 36.00086 -120.47772 1165 73 01/1988 - Gastro Peak
SMNB BP 35.97292 -120.58009 699 282 01/1988 - Stockdale Mountain
VARB BP 35.92614 -120.44707 478 572 01/1988 - 08/19/2003 Varian Well
VARB BP 35.92614 -120.44707 478 298 08/25/2003 - Varian Well
VCAB BP 35.92177 -120.53424 758 200 01/1988 - Vineyard Canyon
CCRB BP 35.95718 -120.55158 595 251 05/2001 - Cholame Creek
LCCB BP 35.98005 -120.51424 640 252 08/2001 - Little Cholame Creek
SCYB BP 36.00938 -120.53660 945 252 08/2001 - Stone Canyon



Table 6.2: Instrumentation of the Parkfield HRSN. Most HRSN sites have L22 sensors and were originally digitized with a RefTek 24 system. After the failure of the WESCOMP recording system, PASSCAL RefTek recorders were installed. In July of 1999, 6 of the PASSCAL systems were returned to IRIS and 4 were left at critical sites. The upgraded network uses a Quanterra 730 4-channel system. For the three new stations (bottom) horizontal orientations are approximate (N45W and N45E) and will be determined more accurately as available field time permits.
Site Sensor Z H1 H2 RefTek 24 RefTek 72-06 Quanterra 730          
EADB Mark Products L22 -90 170 260 01/1988 - 12/1998 12/1998 - 07/1999 03/2001 -          
FROB Mark Products L22 -90 338 248 01/1988 - 12/1998 12/1998 - 07/1999 03/2001 -          
GHIB Mark Products L22 90 failed unk 01/1988 - 12/1998 12/1998 - 07/1999 03/2001 -          
JCNB Mark Products L22 -90 0 270 01/1988 - 12/1998 12/1998 - 06/2001 03/2001 -          
JCSB Geospace HS1 90 300 210 01/1988 - 12/1998 12/1998 - 07/1999 03/2001 -          
MMNB Mark Products L22 -90 175 265 01/1988 - 12/1998 12/1998 - 06/2001 03/2001 -          
RMNB Mark Products L22 -90 310 40 01/1988 - 12/1998 12/1998 - 07/1999 03/2001 -          
SMNB Mark Products L22 -90 120 210 01/1988 - 12/1998 12/1998 - 06/2001 03/2001 -          
VARB Litton 1023 90 15 285 01/1988 - 12/1998 12/1998 - 07/1999 03/2001 -          
VCAB Mark Products L22 -90 200 290 01/1988 - 12/1998 12/1998 - 06/2001 03/2001 -          
CCRB Mark Products L22 -90 N45W N45E - - 05/2001 -          
LCCB Mark Products L22 -90 N45W N45E - - 08/2001 -          
SCYB Mark Products L22 -90 N45W N45E - - 08/2001 -          


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