Berkeley Borehole Networks Cooperative Agreement Overview of Networks Scientific Contributions Needs for Maintaining the Networks

Hayward Fault Network (HFN) 25 borehole stations in total 10 Operating free field (NHFN and mPBO ) sites 3 Operating bridge sites 12 non-operating bridge sites (Caltrans funding will allow operation of some) 2 new sites being developed Sources of Installation Support USGS NEHRP NSF EPRI Caltrans UC/LLNL/LBNL Sources of Operations Support BSL

High Resolution Seismic Network (HRSN) 13 borehole stations in total Sources of Installation Support USGS NEHRP NSF Sources of Operations Support BSL

Waveform Data: HRSN

HRSN: Tremor Observations Nadeau et al., 2004

Waveform Data: NHFN October 19, 2003 Orinda Sequence 4000+ fore- and aftershocks down to M= -2 Courtesy of Peggy Hellweg

Orinda Sequence M3.5 Mainshock -3 -2 -1 1 2 3 x 10-4 x 10 -4 14:35:27 14:35:28 14:35:29 14:35:30 Z H1 H2 UTC Time on 19 October 2003 Ground Velocity (m/s) S-P=0.7 sec Courtesy of Peggy Hellweg

BSL and Collaborative Research Conducted using Data from the Borehole Networks HRSN Repeater Catalog NCSN Catalog Seismic moments, waveforms and event locations are nearly identical, and recurrence times are quasi-periodic Nadeau and McEvilly, 1997

Comparison of slip rate, 2004 coseismic and postseismic slip Inferred Slip Rate from Nadeau and McEvilly (1999)

Korneev et al. 2000 found 6% velocity variation in the fault zone by modeling reflected and transmitted wavefields from vibroseis source

Korneev et al. 2003 modeled station gathers from 1000s of microearthquakes to image fault zone guided waves and fault zone Q structure

Hayward Fault Repeating Earthquakes and Slip Rate Burgmann et al. 2000 - estimates of Hayward fault creep rate from geodetic and characteristically repeating micro earthquakes suggests the seismic potential of the NHF may be less than previously thought.

Other Researchers using Borehole waveform data, data products, and requesting data products SAFOD related research (Ellsworth, Thurber, Roecker, Hole, Li, Vidale, Hickmann, Malin) Beroza – temporal changes in Vp, Vs, and non-linearity Silver – migration of scatterers Vidale – fault healing, anisotropy, fault zone guided waves Korneev – fault zone guided waves Ellsworth – time dependent earthquake forecast models Beeler – compare natural and laboratory repeating event statistics Rubin – requesting event catalogs Abercrombie - waveform and catalog data for scaling research Johnston - correlating strain and tremor occurrence Spudich - tremor catalog to examine UPSAR data * Clear majority of catalog requests are for repeating earthquake and tremor activity since the 2004 Parkfield earthquake

Published Research using Borehole Network Project’s Results

Published Research Using Borehole Network Project Results

Berkeley Borehole Networks Cooperative Agreement Our Predicament Historically we have submitted proposals to NEHRP for both borehole network O/M support and Science. Over the past several years funding has been essentially flat and even cut back moderately while costs, particularly land owner costs have skyrocketed. The funding shortfall has curtailed our ability to support our science and the involvement and training of our students on these projects. Should we keep the networks going or let them die and do research? Additionally, the San Simeon and Parkfield earthquake sequences have greatly increased the numbers of events needing analysis. The present situation is that these events are not being studied.

Needs for Maintaining Borehole Networks Personnel (1 FTE) field and central site technical issues data review and quality control People: Clymer, Nadeau, and Uhrhammer Est. 100k/year Equipment, supplies 4k/year (equivalent to complete system electronics renewal of one site per 5 years, or about 1% of replacement cost of HRSN, NHFN (non-bridge), and mPBO sites) vehicle support 2k/year Land Owner Costs and Telemetry HRSN Kester: $4100/year HRSN Gastro: $6580/year NHFN $5000/year (five free-field sites) Annual Total: 122k + 52% (OH)=185k/yr (currently from NEHRP ~ 135k)

Needed Data Products Merged HRSN, HFN, BDSN, and NCSN phase data catalog In progress at Parkfield (David O.) Same effort on the Hayward fault? Automated pattern recognition catalog of highly similar events Use waveform cross-correlation and pattern recognition to find similar events Requires some development and computer hardware Review of high volume HRSN triggers since the San Simeon earthquake Funding requests to both the USGS and NSF have been declined Repeating earthquake catalog Requires review of automated catalog above to distinguish true repeating events

Review of high volume HRSN triggers since the San Simeon earthquake Triggers per hour Before these earthquake the rate was about 5 triggers per day! Are these additional triggers events at Parkfield or at San Simeon?

Repeating Earthquake Catalog