Subsections


Director's Report

Introduction

During the year 2007-2008, we experienced the largest earthquake in the San Francisco Bay Area since the M 6.9 1989 Loma Prieta earthquake. The $M_w 5.4$ Alum Rock earthquake occurring in the evening of October 30, 2007, local time, was felt widely. It caused surprisingly little damage, however, because its epicenter lay to the southeast of the population centers, and it ruptured southward, away from them. This was a gentle reminder that we live in earthquake country, as well as a good opportunity to test the performance of the Northern California earthquake notification system which we operate jointly with the US Geological Survey in Menlo Park, and that of the Early Warning System currently being tested at the BSL. In contrast, this past year was also marked by the tragic $M_w 7.8$ Sichuan Earthquake (May 12, 2008), which caused 70,000 deaths and 4.8 million homeless, the largest earthquake in China since the 1976 Tangshan earthquake. This earthquake occurred at the eastern boundary of the Tibet Plateau. It is now the subject of intense geophysical study, as it is thought to hold some important keys to the nature of the tectonics and crustal structure of this remarkable region of the world. Researchers at the BSL are actively studying this earthquake.

For those of you familiar with our Annual Report, please skip the background section, which provides a historical introduction to the BSL and has not changed significantly from past years.

Background and Facilities

The Berkeley Seismological Laboratory (BSL), formerly the Berkeley Seismographic Stations (BSS), is the oldest Organized Research Unit (ORU) on the UC 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 UC 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. At the same time, we maintain a vigorous research program on earthquake processes and Earth structure. In addition, the BSL staff spends considerable time on public relations activities, including tours, talks to public groups, responding to public inquiries about earthquakes, and, more recently, World-Wide-Web presence (http://seismo.berkeley.edu/).

UC 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 ($M_{L}$). This was the beginning of a unique historical catalog of regional earthquakes, which continues to grow, 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 the 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 telecommunication and computer technologies made rapid progress, in parallel with broadband instrument development, paper record reading was soon completely abandoned in favor of largely automated digital data analysis.

The current facilities of the BSL have been progressively built over the past two decades, initiated by significant ``upgrade" funding from UC Berkeley in 1991-1995. The BSL currently operates and acquires data, continuously and in real-time, from over 60 regional observatories, which house a combination of broadband and strong motion seismic instrumentation installed in vaults, borehole seismic instrumentation, permanent GPS stations of the Bay Area Regional Deformation (BARD) network, and electromagnetic sensors. The seismic data are fed into the BSL real-time processing and analysis system and are used in conjunction 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. A second important focus of research has been the development of robust methods for quasi-real time, automatic determination of earthquake source parameters, and predicting strong ground motion, using a sparse network combining broadband and strong motion seismic sensors, as well as permanent geodetic GPS receivers. A recent emphasis has been the development of ``earthquake early warning'' capabilities.

The backbone of the BSL operations is a regional network of 32 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 is the Berkeley contribution to the California Integrated Seismic Network (CISN). It also provides a fundamental database for the investigation of three-dimensional crustal structure and its effects on regional seismic wave propagation, which is 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 $\sim 25$ station ``high-resolution" network of borehole seismic sensors located along the Hayward Fault (HFN) and under the Bay Area bridges, operated jointly with the USGS/Menlo Park and linked to the Bridge Safety Project of the California Department of Transportation (Caltrans). The latter has facilitated the installation of sensor packages at 15 bedrock boreholes along 5 East Bay bridges in collaboration with Lawrence Livermore National Laboratory (LLNL). A major science goal of this network is to collect high signal-to-noise data for micro-earthquakes 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 13 element Parkfield borehole seismic array (HRSN), which is providing high quality data on micro-earthquakes, clusters, and, most recently, tremors, and provides an important reference for the 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 the Monterey Bay Aquarium Research Institute (MBARI).

In addition to the seismic networks, the BSL archives and distributes data for the permanent geodetic BARD Network as well as operating and maintaining 30 sites and processing the data from them. Whenever possible, BARD sites are collocated with BDSN sites in order to minimize telemetry costs. In particular, sites continue to be upgraded to 1 Hz sampling. This benefits the development of analysis methods which combine seismic and geodetic data for the rapid estimation of the source parameters of significant earthquakes, which is one focus of BSL research.

Finally, two of the BDSN stations (PKD, SAO) also share data acquisition and telemetry with 5-component electromagnetic sensors installed with the goal of investigating whether tectonic signals can be detected. In 2002-2003, automated quality control software was implemented to monitor the electromagnetic data.

Data from these and other regional networks are archived and distributed 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 (current holdings $\sim 30$ TerraBytes), and are accessible ``on-line" over the Internet (http://www.ncedc.org). Among others, data from the USGS Northern California Seismic Network (NCSN), are archived and distributed through the NCEDC. The NCEDC also compiles, maintains, archives and distributes the ANSS earthquake catalog. Core University funding to our ORU currently provides salary support for 2 field engineers, one computer expert, 2 data analysts, 1 staff scientist and 2 administrative staff. This supports a diminishing portion of the operations of the BDSN and provides seed funding for our other activities. All other infrastructure programs are supported through extra-mural grants primarily from the USGS, NSF, and the State of California, through its Office of Emergency Services (OES). We acknowledge valuable recent contributions from other sources such as Caltrans and PEER, as well as our Earthquake Research Affiliates.

Highlights of 2007-2008

Research Accomplishments

Chapter 2 documents the main research contributions of the past 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 the use of seismological, geodetic, and remote sensing (InSAR) techniques. Productivity continues to be high: over forty papers in refereed journals have been authored or co-authored by BSL researchers in the last year, a steady number compared to previous years.

Once again, the data provided by the borehole stations of the HRSN (Parkfield) network have led to important and exciting results. Following the discovery two years ago of non-volcanic tremors in the Parkfield area, a highlight of this past year's research is the use of a noise correlation approach to document seismic velocity changes correlated with fault zone deformation as measured by GPS, as well as with tremor activity, following the M6.5 San Simeon and M6.0 Parkfield earthquakes (Research Study 32.). This study is a powerful illustration of the successful continuing collaboration between BSL and IPG (Institut de Physique du Globe de Paris) researchers. The collaboration started with a workshop in Paris in January 2007 and is supported on the French side by funding from CNRS through a PICS (Projet international de Coopération Scientifique) and, on the Berkeley side, through a combination of BSL core funds and two France Berkeley Fund awards. A second workshop was held at BSL in December 2007, and a third one is being planned for January 2009 in Paris.

Monitoring of tremor activity at Parkfield continues with new intriguing observations, such as the occurrence of quasi-periodic bursts of tremor activity (Research Study 21.), or the identification of several classes of tremors with different locations (Research Study 28.). On the other hand, acceleration of the recurrence of repeating microseisms since the early 1990's has been confirmed ( Research Study 25.).

BSL researchers made important contributions to the analysis of the data in the wake of the tragic 08/06/07 Crandall Canyon mine collapse. Through the use of seismic broadband waveform inversion tools developed at BSL, Sean Ford and Doug Dreger, with LLNL collaborator Bill Walter, demonstrated that the recorded seismic signals could not be due to a tectonic earthquake, but rather the collapse itself (Research Study 30.).

The occurrence of the 10/30/07 $M_w$ 5.4 Alum Rock earthquake, widely felt in the San Francisco Bay Area, provided an opportunity to demonstrate the capabilities of both the Northern California real time systems (Research Study 22.) and the ElarmS earthquake Early Warning methodology (Research Study 26.). It also highlighted the possibility of slip transfer between the Hayward and Calaveras faults (Research Study 3.).

The comparison of low frequency noise at the ocean floor broadband station MOBB and the island station FARB has provided important constraints on the generation of this noise and its relation to infragravity waves in the ocean (Research Study 14.).

BSL researchers continue to investigate the recently widely advertised Accelerated Moment Release hypothesis (AMR) and have documented the high sensitivity of ``observed'' AMR to the choice of free parameters considered (Research Study 4.).

On the global seismology front, a new method has been developed to separate the effects of depth dependence and intrinsic frequency dependence on seismic attenuation as measured using free oscillations (Research Study 20.) and progress is being made in the construction of tomographic models at global and regional scales, using 3D numerical wave propagation computations (Research Studies 12. and 17.).

Finally, the development of new electronics for the STS-1 seismometer has been completed. BSL researchers and engineers have been involved in the testing and evaluation of these successful new electronics (Chapter 3, Section 9) and in particular, have already utilized their convenient remote calibration capabilities at several BDSN stations.

Infrastructure and Earthquake
Notification

As in previous years, BSL's infrastructure development efforts have centered around several major projects:

The main goal of the CISN (see Chapter 3, Section 2) is to ensure a uniform system for earthquake monitoring and reporting in California. The highest priority, from the point of view of emergency responders in California, is to improve the robustness of statewide real-time notification and to achieve a uniform interface across the State to the California OES and other emergency responders. This represents a major challenge, as the CISN started as a heterogeneous collection of networks with disparate instrumentation, software systems, and cultures. Over the past few years, much effort has gone into developing coordinated software between Southern and Northern California and, in Northern California, between Berkeley and USGS/Menlo Park. These two institutions are joined together in the Northern California Earthquake Management Center (NCEMC). A highlight of the past year has been the re-installation of five sites (SUTB, RAMR, HATC, HAST, HELL) previously occupied by USArray Travelling Array, with permanent broadband equipment acquired through FEMA grants and OES funds. In particular, BSL engineers improved the installation design to remove condensation inside the vaults, an important issue for long term deployments. One other site is awaiting transfer of permit to BSL, while two additional former USArray sites are awaiting funding to acquire permanent seismic equipment.

2007-2008 is the last year of the 3 year funding cycle for CISN from the Office of Emergency Services (OES). In the past year, progress has been made on unifying the way leap seconds are treated in Southern and Northern California, and on magnitude calibration across the state. The Jiggle analysis software has been modified and installed in Northern California in November 2006 and will be offered to other regions of the Advanced National Seismic System soon. Data from the Northern Hayward Fault Network have been integrated into the Northern California Seismic System.

BSL staff continue to spend considerable efforts in organizational activities for CISN, notably by participating in the CISN Project Management Group (Neuhauser and Hellweg), which includes weekly 2 hour phone conferences, and the Standards Committee (Neuhauser-chair, Hellweg, Lombard), which strives to define and coordinate software development tasks. Romanowicz and Hellweg serve on the CISN Steering Committee. 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.

The Parkfield borehole network (HRSN, see Chapter 3, Section 4) continues to play a key role in support of the Earthscope SAFOD (San Andreas Fault Observatory at Depth) drilling project, by providing low noise waveforms for events in the vicinity of the target drilling zone. Efforts have been started this year to minimize the costs of this network, in particular the land fees, by moving key elements of the telemetry away from a very costly site.

The BARD continuous GPS (C-GPS) network (see Chapter 3, Section 5) has focused its efforts on the development of local collaborations to densify the network and reduce telemetry costs associated with the installation of new stations. Also, BSL engineers have been working on the design of meteorological sensors to be installed at GPS sites. Corrections using data from these sensors will help minimize the effects of the troposphere on BARD solutions.

Finally, the NCEDC has continued to expand its data holdings and enhance access to the data; in particular, we have made progress in archiving continuous seismograms read from NCSN tapes, to satisfy numerous requests from researchers interested in looking for non-volcanic tremors in the background noise, as well as for the study of teleseisms, and have ported the entire NSCN earthquake catalog into the CISN database schema.

BSL staff news

Changes in BSL staff in 2007-2008 are as follows.

The following graduate students associated with BSL completed their PhD's in the past year: Mei Xue, now a faculty member at Tongji University in Shanghai, and Karl Kappler, who is still around. Eileen Evans obtained her MS in May 2008 and worked through the summer before starting a PhD at Harvard this fall.

In the global seismology group, Aimin Cao, graduate student and later post-doc left for Rice University, and Fabio Cammarano left for ETH (Zurich). There have been several new arrivals: Laurent Stehly joined the global seismology group as a post-doc in January, and Paul Cupillard in June. Laurent obtained his PhD at the Universite Joseph Fourier in Grenoble, and Paul, at IPG in Paris. They bring expertise on the use of noise cross-correlations for structure studies, and on the Spectral Element Method, respectively. Zhao Zheng (Allen), from Peking University and Sanne Cottaar, from Utrecht University, have joined the group as graduate students.

Bob Uhrhammer, who started working at the Berkeley Seismographic Stations in 1975, retired in January 2008, and has come back to work part time as a retiree appointee. His help in training Taka'aki Taira, our new staff seismologist who arrived in August, is invaluable. Dr. Taira obtained his PhD at Hokkaido University in Japan, followed by post-docs at Carnegie and the Univ. of Utah. His research interests include earthquake nucleation and rupture processes, as well as fault rheology and time dependent phenomena in fault zones.

BSL hosted the following visiting scientists in 07-08: Jean Pierre Vilotte (IPG Paris), Georges Poupinet (Grenoble, France), Hui-Hsuan (Kate) Chen (National Taiwan Normal University, Taiwan), DV Chandrasekhar (National Geophysical Research Institute, Hyderabad India), Luca Malagnini (Istituto Nazionale di Geofisica e Vulcanologia, Italy), Paramesh Banerjee (Newcastle University, England), Fabian Walter (ETH Zurich), Shweta Sangewar (Indian Institute of Technology, India), Andrea Cannata (University of Catania, Italy), Stefano Gresta (University of Catania, Italy), and the following summer 07 interns: Jake Lippman, from UC Davis, and Andrew Tran, from Cal Poly.

Alexey Kireev left BSL in early April. Oleg Khainovski, a 2006 UCB engineering Physics graduate, was hired in August as a programmer to work on the CISN and Early Warning projects. Angela Chung left the BSL in June to pursue a PhD in geophysics at Stanford University.

Acknowledgements

I wish to thank our technical and administrative staff, scientists and students for their efforts throughout the year and 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 Kate Lewis (Conner), Kristen Jensen and Jennifer Taggart.

I also wish to specially thank the individuals who have regularly contributed to the smooth operation of the BSL facilities: Mario Aranha, Rich Clymer, Angela Chung, Doug Dreger, John Friday, Jarrett Gardner, Peggy Hellweg, Nicolas Houlié, Bill Karavas, Alexei Kireev, Rick Lellinger, Pete Lombard, Kevin Mayeda, Rick McKenzie, Bob Nadeau, Doug Neuhauser, Charley Paffenbarger, Jennifer Taggart, Bob Uhrhammer, and Stephane Zuzlewski, and in the administrative office, Kristen Jensen, Kate Lewis (Conner), Tina Barber-Riggins, and Yolanda Andrade. I also wish to thank our undergraduate assistants, Eileen Evans, Sarah Minson, Eric Winchell, and Jozef Matlak for their contributions to our research and operations activities.

I am particularly thankful to Jennifer Taggart and Peggy Hellweg, for their help in putting together this Annual Report.

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




Barbara Romanowicz
September 30, 2008

Berkeley Seismological Laboratory
215 McCone Hall, UC Berkeley, Berkeley, CA 94720-4760
Questions or comments? Send e-mail: www@seismo.berkeley.edu
© 2007, The Regents of the University of California