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Director's Report

Subsections

Figure 1: Map illustrating the distribution of stations in the BDSN, NHFN, HRSN, BARD, and Mini-PBO networks in northern and central California. A star indicates the location of the MOBB deployment.
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Background and Facilities

The Berkeley Seismological Laboratory (BSL), formerly the Berkeley Seismographic Station (BSS), is the oldest Organized Research Unit (ORU) on the U. C. Berkeley campus. Its mission is unique in that, in addition to research and education in seismology and earthquake-related science, it is responsible for providing timely information on earthquakes (particularly those that occur in northern and central California) to the U.C. Berkeley constituency, the general public, and various local and state government and private organizations. The BSL is therefore both a research center and a facility/data resource, which sets it apart from most other ORUs. A major component of our activities is focused on developing and maintaining several regional observational networks, and participating, along with other agencies, in various aspects of the collection, analysis, archival and distribution of data pertaining to earthquakes, while maintaining a vigorous research program on earthquake processes and Earth structure. In addition, the BSL staff spends considerable time with public relations activities, including tours, talks to public groups, responding to public enquiries about earthquakes and, more recently, World-Wide-Web presence (http://seismo.berkeley.edu/).

U.C. Berkeley installed the first seismograph in the Western Hemisphere at Mount Hamilton (MHC) in 1887. Since then, it has played a leading role in the operation of state-of-the-art seismic instruments and in the development of advanced methods for seismic data analysis and interpretation. Notably, the installation, starting in 1927, of Wood-Anderson seismographs at 4 locations in northern California (BKS, ARC, MIN and MHC) allowed the accurate determination of local earthquake magnitude ($M_L$) from which a unique historical catalog of regional earthquakes has been maintained to this day, providing crucial input to earthquake probabilities studies.

Over the years, the BSS continued to keep apace of technological improvements. The first centrally telemetered network using phone lines in an active seismic region was installed by BSS in 1960. The BSS was the first institution in California to operate a 3-component "broadband" system (1963). Notably, the BSS played a major role in the early characterization of earthquake sources using "moment tensors" and source-time functions, and made important contributions to the early definitions of detection/discrimination of underground nuclear tests and to earthquake hazards work, jointly with UCB Engineering. Starting in 1986, the BSS acquired 4 state-of-the-art broadband instruments (STS-1), while simultaneously developing PC-based digital telemetry, albeit with limited resources. As the telecommunication and computer technology made rapid progress, in parallel with broadband instrument development, paper record reading could be completely abandoned in favor of largely automated digital data analysis.

The current modern facilities of BSL have been progressively built over the last 12 years, initiated by significant "upgrade" funding from U.C. Berkeley in 1991-1995. The BSL currently operates and acquires data, continuously and in real-time, from over 40 regional digital seismic stations, including 20 located in boreholes, 21 permanent GPS stations of the BARD network, and 2 electromagnetic stations. The seismic data are fed into the BSL real-time processing and analysis system and are used in conjuction with data from the USGS NCSN network in the joint earthquake notification program for northern California, started in 1996. This program capitalizes on the complementary capabilities of the networks operated by each institution to provide rapid and reliable information on the location, size and other relevant source parameters of regional earthquakes. In recent years, a major emphasis in BSL instrumentation has been in densifying the state-of-the-art seismic and geodetic networks, while a major on-going emphasis in research has been the development of robust methods for quasi-real time automatic determination of earthquake source parameters and predicted strong ground motion, using a sparse network combining broadband and strong motion seismic sensors, as well as permanent geodetic GPS receivers.

The backbone of the BSL operations is a regional network of 20+ digital broadband and strong motion seismic stations, the Berkeley Digital Seismic Network (BDSN), with continuous telemetry to UC Berkeley. This network provides the basic regional data for the real-time estimation of location, size and rupture parameters for earthquakes of M 3 and larger in central and northern California, within our Rapid Earthquake Data Integration (REDI) program. It also provides a fundamental database for the investigation of three-dimensional crustal structure and its effects on regional seismic wave propagation, ultimately crucial for estimating ground shaking for future earthquakes. Most stations also record auxiliary temperature/pressure channels, valuable in particular for background noise quality control. Complementing this network is a 20+ station "high-resolution" network of borehole seismic sensors along the Hayward Fault (HFN), operated jointly with the USGS/Menlo Park and linked to the Bridge Safety Project of the California Department of Transportation, which has made possible the installation of sensor packages at 15 bedrock boreholes at 5 east-bay bridges in collaboration with LLNL. A major science goal of this network is to collect high signal-to-noise data for microearthquakes along the Hayward Fault to gain insight into the physics that govern fault rupture and its nucleation. The BSL is also involved in the operation and maintenance of the Parkfield borehole seismic array (HRSN), which is yielding enlightening results on quasi-periodic behavior of microearthquake clusters and important new constraints on earthquake scaling laws and is currently playing an important role in the characterization of the site for the future San Andreas Fault Observatory at Depth (SAFOD). Since April 2002, the BSL is also involved in the operation of a permanent broadband ocean bottom station, MOBB, in collaboration with MBARI (Monterey Bay Aquarium Research Institute).

In addition to the seismic networks, the BSL is involved in data archival and distribution for the permanent geodetic BARD (Bay Area Regional Deformation) Network as well as the operation and maintenance, and data processing of 21 out of its 70+ sites. Whenever possible, BARD sites are collocated with BDSN sites in order to minimize telemetry costs. In particular, the development of analysis methods combining the seismic and geodetic data for the rapid estimation of source parameters of significant earthquakes has been one focus of BSL research.

Finally, two of the BDSN stations also share data acquisition and telemetry with 5-component electro-magnetic sensors installed with the goal of investigating the possibility of detection of tectonic signals.

Archival and distribution of data from these and other regional networks is performed at the Northern California Earthquake Data Center (NCEDC), operated at the BSL in collaboration with USGS/Menlo Park. The data reside on a mass-storage device (2.5 Terabyte capacity), and are accessible "on-line" over the Internet (http://www.quake.geo.berkeley.edu). Among others, data from the USGS Northern California Seismic Network (NCSN), are archived and distributed through the NCEDC. The NCEDC also maintains, archives and distributes the ANSS/CNSS earthquake catalog.

Core University funding to our ORU provides salary support for 3 field engineers, one computer expert, 2 data analysts, 1 staff scientist and 2 administrative staff. This covers the basic needs of the operations of the BDSN and seed funding for our other activities. All other programs are supported through extra-mural grants primarily from the USGS and NSF, and in the past year, the Office of Emergency Services (OES). We acknowledge valuable recent contributions from other sources such as Caltrans, the CLC program, PEER, as well as our Earthquake Research Affiliates.

Highlights of 2001-2002

Infrastructure and Earthquake Notification

Three major projects of the BSL deserve attention in 2001-2002: CISN, "Mini-PBO", and the ocean bottom observatory MOBB.

A focus of the past year has been the planning and initial implementation of the BSL component of the CISN (California Integrated Seismic Network), with support in FY'02 (received in April 2002) from the State of California through the Office of Emergency Services (OES) (Chapter 3).

A major goal of the CISN is to ensure a more uniform system for earthquake monitoring in California, through the improvement of seismic infrastructure in northern California and continued maintenance of the TriNet system in southern California. Another major goal is to integrate the earthquake monitoring and reporting efforts in the State, using compatible software and creating a single catalog. A present focus is to improve the robustness of statewide rapid notification and work with the California OES and other emergency responders to maximize the use and benefit of this real time seismic information.

In anticipation of the pending funding, BSL staff conducted searches and surveys to identify potential sites for new broadband stations, two of which have been selected and permitted, and will be installed as soon as the equipment becomes available. With very little time to spend the funds from OES in FY'02 (3 months), the BSL purchased equipment for 5 BDSN sites, and focused efforts on the development of software to re-design the USGS/UCB joint earthquake notification system and move towards merging the systems now in operation at each of the two institutions. Initial steps have been taken towards exchanging data in real-time with southern California, involving 10 stations in each sub-region.

BSL staff have spent considerable efforts in organizational activities for CISN, notably by participating in the CISN Project Management Group (Gee) and the Standards Committee (Neuhauser-chair, Gee, Lombard). Romanowicz rotated off as chair of the CISN Steering Committee, but still remains involved. The CISN also represents California as a designated region of ANSS (Advanced National Seismic System) and the BSL is actively involved in planning activities for the ANSS.

This past year has been marked by a climax in the installation efforts towards the "Mini-PBO" project (Chapter 9), a project supported partly by a grant from the NSF/MRI program, in collaboration with CIW, UCSD and USGS/Menlo Park, with matching from UCB and these other institutions as well as Caltrans (http://seismo.berkeley.edu/bdsn/mpbo_overview.html). This project's focus is the installation of a network of multi-parameter stations in the San Francisco Bay Area to monitor the evolution of tectonic strain in time and space - a pilot project for the Plate Boundary Observatory (PBO) currently being planned in the framework of an NSF/MRE proposal. "Mini-PBO" instrumentation comprises 3 component borehole strainmeters and seismometers, GPS receivers and auxiliary sensors (such as pore pressure, temperature, and tilt). The data are telemetered to UC Berkeley and distributed through the NCEDC. The first two holes were drilled in early summer 2001 and instrumented in 2002. Three additional holes were drilled in the summer of 2002, with considerable involvement of BSL staff (Murray, Basset, W. Johnson, Karavas) and are currently in various stages of instrument installation. The initial goal of 10 stations has been reduced to 6 due to budgetary constraints related to considerable cost-overruns in drilling. The plan is for the 6th and last hole to be drilled with Caltrans's help in the Fall of 2002.

The MOBB (Monterey Ocean bottom Broad Band observatory) is a collaborative project between the BSL and MBARI and builds upon the experience gained in 1997 through the MOISE project, which involved the temporary deployment of a broadband ocean bottom system in Monterey Bay. MOBB is now a permanent installation and comprises a broadband seismic package (Guralp CMG-1), a battery and recording package, as well as auxiliary sensors: a current-meter and a DPG (differential Pressure Gauge). The system was assembled and tested at BSL in early 2002, and successfully deployed in April 2002 (Chapter 10). In particular, extensive testing and seismometer insulation procedures were developed at Byerly Vault on the UCB campus prior to deployment (Chapter 11).

In the past year, the BSL has been closely involved in the coordination of site characterization for the SAFOD drilling project in the Parkfield area (Chapter 6). In particular, data from the new HRSN borehole site at CCRB, located 2 km south of the target drilling site, is recording signals from the pilot drilling project which may prove crucial for guiding drilling of the SAFOD hole. The new earthquake triggering scheme for the HRSN network has also been finalized, with the goal of reducing the bandwidth necessary for data telemetry to BSL.

Other accomplishments in the past year include the deployment of a new BDSN station (HUMO - Chapter 4) in southern Oregon, in collaboration with USGS/NSN and IRIS programs, and a new BARD station at OHLN (Ohlone Park), the first GPS station to be mounted on top of a Mini-PBO borehole (Chapter 8). A single frequency (L1) GPS receiver profile has been installed across the Hayward Fault, with assistance from UNAVCO engineers, to investigate the resolution power of this cost-effective way to monitor creep on the fault.

The NHFN network project has seen the upgrade of the infrastructure of 7 stations on the Bay Bridge (Chapter 5), in anticipation of the deployment of the Quanterra recording systems and the development of an algorithm to identify highly similar microearthquakes on the Hayward Fault based on complex spectral phase coherency.

On the NCEDC front (Chapter 13), we continue archiving and distribution on-line of data from expanding BDSN, NHFN, HRSN, BARD, Mini-PBO, and other networks and data collections in northern California. A notable addition is the continuous acquisition and archiving of broadband data from 4 stations operated by the University of Nevada, Reno, and 7 stations operated by the USGS Menlo Park. The USGS "low frequency" geophysical time series data collection (strain, creep, magnetic field, water level, etc.) is now accessible in standard MiniSEED format and instrument responses are available for over 90% of the archived channels. The NCEDC also started to archive and make publically available the state-of-health channels for the BDSN/NHFN/MPBO stations. The NCEDC is participating in the UNAVCO-sponsored GPS Seamless Archive Centers (GSAC) initiative, which is developing common protocols and interfaces for the exchange and distribution of continuous and survey-mode GPS data, and is now both a primary provider for BARD/BSL data, a wholesale collection point for other northern California GPS data, and a retail center for all GSAC data.

The BSL continues to collaborate with the USGS/Menlo Park in the generation of ShakeMap for northern California and has been developing and implementing successive upgrades to this system, integrated within the REDI environment (Chapter 12). ShakeMap is calculated routinely for magnitude 3.5 and larger events in northern California. Any magnitude 5.0 or larger will now also trigger the finite-fault processing.

Finally, the BSL has taken steps to use automatically produced moment magnitude ($M_w$), when available, to supplement estimates of local magnitude ($M_L$), which is particularly useful in the case of significant earthquakes. $M_w$ has been routinely produced within the REDI system for many years, but, until now, not broadcast as the "official magnitude", due in part to questions about the reliability of the automatic solutions. In the past year, the robustness of the moment tensor codes has been improved, facilitating the transition to official broadcasting.

Research Accomplishments

Part III documents the main research contributions of the last year. Research at the BSL spans a broad range of topics, from the study of microseismicity at the local scale to global deep earth structure, and includes seismological, geodetic and remote sensing (InSAR) techniques.

In this past year, Nadeau and collaborators have continued investigation of fault zone characteristics from the analysis of microearthquakes at Parkfield, and extended their scaling of recurrence times and moments of microearthquakes over 15 orders of magnitude in seismic moment. They have also been involved in determining the detailed seismic structure around the future site of the SAFOD. These microseismicity techniques are now also being extended to the study of faults in the San Francisco Bay Area and to the investigation of the brittle-ductile transition zone and its rheological properties (Rolandone et al.). At a very different, global scale, Romanowicz and Ruff re-examined the scaling of moment to length of large strike-slip earthquakes and found that the data fall into two distinct classes indicative of stronger (mostly oceanic) or weaker (mostly continental) faults.

For the second year, Uhrhammer has been engaged in a major effort to transcribe Berkeley historical earthquake data dating back to 1910, and stored on cards or paper records, to computer readeable format, with the goal of obtaining more complete seismicity catalogs and better characterize the evolution of seismicity with time and space. An initial focus on the San Francisco Bay Area is being extended to northern California. Five undegraduate students have been involved in this project.

A study by Freed has investigated earthquake triggering of other earthquakes on the San Andreas Fault in southern California.

In a novel application, Schmidt and Bürgmann have used InSar data to study land uplift and subsidence in the Santa Clara Valley, highlighting the spatial complexity of the aquifer system, while Johanson and Bürgmann are using InSar to detect slow earthquakes on the creeping sections of the San Andreas Fault system. Murray is engaged in resurveing 40 GPS monuments that were last surveyed in 1993-95 to further characterize crustal deformation in the northern San Andreas Fault system and D'Alessio and collaborators are using GPS in survey mode to monitor motion on the Hayward Fault, and obtain a creep rate of 4.2 mm/year at the Berkeley Memorial Stadium. The BSL has also shared its expertise by collaborating in the deployment of a new regional continuous GPS network in northern Italy, around the epicenter of the damaging 1976 Friuli earthquake.

Several studies of earthquakes at the regional scale are reported: an investigation of the influence of fluids on faulting at Long Valley Caldera by Templeton and Dreger; a study of the mechanisms of major aftershocks of the 1999 Chi-Chi earthquake in Taiwan by Chi and Dreger; adaptation of the BSL real time moment tensor techniques to the monitoring of nuclear explosions in the framework of the International Monitoring System (Hellweg et al.); and the on-going development of a method to locate the sources of continuous low-frequency background Earth oscillations (Rhie and Romanowicz).

In a transition to studies of Earth structure, Rhie and Dreger report on their waveform modeling of the seismic velocity structure in Northern California. At the global scale, we report progress in global anelastic tomography, resulting in a new model of attenuation in the upper-mantle, which has revealed the connection of lowermost mantle "superplumes" with upwelling regions in the upper mantle and hotspots (Gung and Romanowicz); with Gung and Panning, we have started to investigate radial anisotropy at the global scale, and have found that discrepancies in different global tomographic models of the upper mantle can be reconciled if anisotropy beneath lithospheric roots (depth range 250-400km) is considered; we have also started investigating anisotropy at greater depths in the mantle and extended our S modeling techniques to include inversion for P velocity (Panning and Romanowicz). Rousset and Romanowicz are developing a method based on a neigbourhood algorithm to investigate the range of plausible models for degree 2 heterogeneity in density in the mantle; with Toh and Capdeville, we are making progress in exploiting the rich capabilities of the coupled mode-spectral element method to study complex 3D structure at the base of the mantle; finally, with Tkalcic, we documented sharp, uncorrelated, lateral variations in P and S velocities at the base of the mantle.

Acknowledgements

I wish to thank our technical and administrative staff, scientists and students for their contributions to this annual report. Individual contributions to activities and report preparation are mentioned in the corresponding sections, except for the Appendix section, prepared by Christina Jordan and Eleanor Blair.

Starting July 1st, 2002, Professor Douglas Dreger has been appointed Associate Director of the BSL. In particular, Doug has assumed overall responsibility, with help from Bob Nadeau, for the HRSN and NHFN programs, following Professor McEvilly's death.

I also wish to specially thank the individuals who regularly contribute to the smooth operation of the BSL facilities: André Basset, Sierra Boyd, Rich Clymer, Doug Dreger, John Friday, Lind Gee, Wade Johnson, Bill Karavas, Pete Lombard, Rick McKenzie, Mark Murray, Bob Nadeau, Doug Neuhauser, Charley Paffenbarger, David Rapkin, Cathy Thomas, Bob Uhrhammer, and Stephane Zuzlewski.

Eleanor Blair, Heather Read and Christina Jordan continue to provide valuable support to the administration of our lab, with help from Patricia Villa. The BSL administrative office has continued to assist the EPS department administrative personnel, in a continued period of transition in that office. We are also grateful to Ruth Saha, who helped out during a period of high demand.

In 2001-2002, there have been some changes in BSL personnel. Dr Fumiko Tajima left in May 2002 to become a professor at Hiroshima University in Japan. Hrvoje Tkalcic also left in May for a post-doctoral position in sunny San Diego. Steve Chu graduated in December 2001 and left in May to work for a start-up company. We also experienced some turnover in the Adminstrative office, with the departure of Keia Shipp and Aric Mayer.

We welcome three new post-docs at the BSL: Maurizio Battaglia, Andy Freed, and Frederique Rolandone. We also welcome four new staff members: Heather Read and Patricia Villa joined the adminstrative office, Cathy Thomas became part of the field engineering team, and Jim Yan joined the BSL as a programmer. Unfortunately, because of the temporal limitations of CISN funding, Jim Yan left at the end of June.

I also wish to thank our undergraduate assistants S. Chu, J. Epstein, T. Fournier, L. Krain, K. Spiller, G. Treves, and M. Wilmarth for their contributions to our research and operational activities. I am particularly thankful to Lind Gee and Christina Jordan for their help in putting together this Annual Report.

Lane Johnson retired in June 2002 from his teaching position in the Department of Earth and Planetary Science. He will continue research activities at LBNL. I wish to thank him in particular for his role as Acting Director of the BSL during my sabbatical in the spring of 2002 and wish him well in his retirement.

Finally, I wish to express my deep sorrow upon Professor Tom McEvilly's death (Chapter 2). Professor McEvilly passed away on 02/22/2002 after a courageous fight with cancer. Tom's death is a considerable loss for the BSL. We miss his leadership in research, in recent years focused on the Parkfield program, and his cheerful and energizing presence.

The Annual Report of the Berkeley Seismological Laboratory is available on the WWW at http://seismo.berkeley.edu/annual_report/.




Barbara Romanowicz

Sept 10, 2002

Glossary of Common Acronyms

Table 1.1: Standard abbreviations used in this report.
Table: continued
Acronym Definition
   
AGU American Geophysical Union
ANSS Advanced National Seismic System
BARD Bay Area Regional Deformation
BDSN Berkeley Digital Seismic Network
BSL Berkeley Seismological Laboratory
BSS Berkeley Seismographic Station
CISN California Integrated Seismic Network
CGS California Geological Survey
CLC Campus Laboratory Collaboration
CNSS Council of the National Seismic System
EM Electromagnetic
EPRI Electric Power Research Institute
FBA Force Balance Accelerometer
FIR Finite Impulse Response
FRAD Frame Relay Access Device
GPS Global Positioning System
HFN Hayward Fault Network
HRSN High Resolution Seismic Network
IGS International Geodetic Service
IMS International Monitoring System
InSAR Interferometric Synthetic Aperture Radar
IRIS Incorporated Research Institutions for Seismology
ISC International Seismological Center
ISTAT Integrating Science, Teaching, and Technology
JPL Jet Propulsion Laboratory
LBNL Lawrence Berkeley National Laboratory
LLNL Lawrence Livermore National Laboratory
MBARI Monterey Bay Aquarium Research Institute
MHH Murdock, Hutt, and Halbert
MOBB Monterey Ocean bottom BroadBand observatory
MOISE Monterey Bay Ocean Bottom International Seismic Experiment
MPBO Mini-Plate Boundary Observatory
MRI Major Research Initiative
MRE Major Research Equipment
MT Magnetotelluric
NCEDC Northern California Earthquake Data Center
NCSN Northern California Seismic Network
NEHRP National Earthquake Hazards Reduction Program
NEIC National Earthquake Information Center
NHFN Northern Hayward Fault Network
NGS National Geodetic Survey
NSF National Science Foundation
NSN National Seismic Network
OES Office of Emergency Services
ORU Organized Research Unit
PBO Plate Boundary Observatory
PEER Pacific Earthquake Engineering Center
PH Pilot Hole
PPE Parkfield Prediction Experiment
PSD Power Spectral Density
REDI Rapid Earthquake Data Integration
SAF San Andreas Fault
SAFOD San Andreas Fault Observatory at Depth
SAR Synthetic Aperture Radar
SCEC Southern California Earthquake Center
SCEDC Southern California Earthquake Data Center
SCIGN Southern California Integrated GPS Network
SEED Standard for the Exchange of Earthquake Data
SHFN Southern Hayward Fault Network
SIO Scripps Institutions of Oceanography
SNCL Station Network Channel Location
SSA Seismological Society of America
STP Seismogram Transfer Program
UCB University of California at Berkeley
UNAVCO University NAVSTAR Consortium
UrEDAS Urgent Earthquake Detection and Alarm System
USGS United States Geological Survey



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