Subsections


Director's Report

Figure 1.1: 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 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, 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://www.seismo.berkeley.edu/seismo/).

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 13 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 60 regional observatories, housing a combination of broadband and strong motion seismic instrumentation installed in vaults, borehole seismic instrumentation, permanent GPS stations of the BARD network, and electromagnetic instrumentation. 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, 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 25+ 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 and 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, 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 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 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 yielding enlightening results on quasi-periodic behavior of micro-earthquake 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 22 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 (PKD, SAO) also share data acquisition and telemetry with 5-component electromagnetic sensors installed with the goal of investigating the possibility of detection of tectonic signals. In 2002-2003, an automated quality control software was implemented to monitor the electromagnetic data.

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 (4.5+ 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 has suffered from permanent budget cuts to research programs from the State of California, and 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 programs are supported through extra-mural grants primarily from the USGS and NSF, and in the past three years, the Governor's 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 2003-2004

Infrastructure and Earthquake
Notification

In 2003-2004, BSL's activities have centered around two major projects: the continuation of CISN and the deployment in California of the BigFoot component of USArray/Earthscope. In this context, we have continued our efforts to expand the northern California broadband network while trying to reduce the costs of operation, in the wake of significant cuts to our University funding. In addition, we have continued the installation of the remaining "mini-PBO" sites and the expansion of the NCEDC database, and have taken the first steps towards designing an integrated telemetry link from Parkfield, CA, in particular in anticipation of our collecting and archiving data from the San Andreas Fault Observatory at Depth (SAFOD) program of Earthscope. The M 6.5 San Simeon earthquake of 12/22/03 was an opportunity to test the capabilities of CISN as well as those of the HRSN, and those of recently developed research tools, as will be described in the Research Section.

The main goal of the CISN (Chapter 2) is to ensure a more 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 culture. Therefore, in the past year, as previously, the emphasis has been on software development. Notably, we have made significant progress on merging the USGS/Menlo Park and BDSN networks in northern California. We note also, that the coordinated software development across CISN partners over the last 3 years is bearing its fruits: for example, we now have a pool of staff members in the northern and southern processing centers that have a sufficient knowledge of each other's software to be in a position to help each other or serve as back-up in the case of a failure. This contributes to the improvement in the robustness of the statewide system.

Another goal of the CISN program is to improve the seismic infrastructure in northern California. Because funding is limited, this goal is continued at a slower pace. Nevertheless, we have started the construction of two new broadband/strong motion stations in 2003-2004 (Alder Springs and Marconi). These sites should be completed by the end of 2004, in spite of considerable delays due to the shortage of personnel.

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

In the last two years, a major component of our activities has been coordinating with IRIS on the deployment in northern California of $ 50$ temporary broadband stations of the BigFoot array of Earthscope. The BSL will contribute many (15+) of its existing sites to this effort and is involved in the joint siting of 10 new sites. These sites will be permitted by BSL and constructed by USArray. When BigFoot leaves California in 2007, these sites will be available for permanent BSL installation, provided funding is found for the seismic instrumentation. In 2003-04, we have helped permit one station in the vicinity of the epicenter of the San Simeon earthquake. This station (located at the Hastings Reserve) is now operational. We are currently pursuing the permitting of other sites.

This past year has seen progress towards the completion of the Mini-PBO project (Chapter 7), a project supported partly by a grant from the NSF/MRI program, in collaboration with CIW, UCSD and USGS/Menlo Park, with matching from participating institutions (including UCB) as well as Caltrans (http://www.seismo.berkeley.edu/seismo/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) component of Earthscope (a national infrastructure program funded by NSF within its Major Research Equipment program). The installation of the 5 borehole strainmeters and seismomters, as well as auxiliary sensors (pore pressure, temperature and tilt) was completed in 2002-03, but 3 of the sites lacked GPS receivers as well as continuous telemetry to UC Berkeley for distribution through the NCEDC. Four sites are completed, while the remaining one is in the final stages of the installation of power and communications systems.

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 3). Extensive testing of seismometer insulation procedures, which were developed at Byerly Vault on the UCB campus prior to MOBB deployment (Chapter 8) have now been applied to three similar systems destined for the KECK project (Juan de Fuca plate), in collaboration with University of Washington at Seattle. In February 2004, we experienced the failure of one of our horizontal components. Thanks to the availability of one of the Keck instruments and the willingness of the MBARI crew, we were able to swap the seismic package in May 2004 and send it for repair. It has now been successfully reinstalled. The MOBB is scheduled to be hooked up to the MARS cable which will be installed in Monterey Bay in the Fall of 2005.

The BSL has continued to be involved in the coordination of site characterization for the SAFOD drilling project in the Parkfield area (Chapter 5). In particular, the HRSN has played a key role in providing seismic waveform data for a series of active source experiments conducted to characterize the SAFOD drilling site. These high quality waveform data are complementary to those, by nature more noisy, recorded by temporary deployments at the surface. Efforts have continued to reduce noise levels at the borehole sites to increase the detection level of magnitude -1.0 and lower earthquakes. The occurrence of the M6.5 San Simeon earthquake on 12/22/03, with its numerous aftershocks, has both significantly complicated the routine data processing task for HRSN and provided an opportunity to rethink the traditional processing schemes implemented more than 15 years ago.

The NHFN network project has focused on the development of new algorithms to lower the detection threshold of microseisms along the Hayward Fault (Chapter 4). This includes a pattern recognition approach, a phase coherency method and a phase onset time detector. Completion of the Bay Bridge sites has been hampered by the shortage of personnel, concurrent with the necessity to concentrate our efforts on the highly visible HRSN network and the intensive efforts in preparation for the SAFOD drilling.

The NCEDC (Chapter 10), continues archiving and distribution of on-line of data from expanding BDSN, NHFN, HRSN, BARD, Mini-PBO, and other networks and data collections in northern California and Nevada. A major accomplishment in the last year is making the entire collection of NCSN waveform data available (1984-2003) through the NCEDC archive (including instrument responses for all NSCN stations). These waveform data can now also be retrieved by a query based on event-id. There have also been notable enhancements in the $BREQ\_FAST$ and $NetDC$ data retrieval interfaces, that now provide access to NCSN waveform data in SEED format.

The BSL continues to collaborate with the USGS/Menlo Park in the generation of ShakeMap for northern California and to develop and implement successive upgrades to this system, integrated within the REDI environment (Chapter 9). 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. The 12/22/03 M6.5 San Simeon earthquake provided an opportunity to demonstrate the capabilities of the automatic finite fault processing system, which is triggered for M 5.0 and larger earthquakes.

Finally, through Dr Lind Gee's efforts, BSL has been actively involved in the preparation of UC Berkeley's participation in the commemoration activities of the centennial anniversary of the 1906 earthquake (Chapter 11). These activities include a joint SSA/EERI/DRC conference to be held in San Francisco in April 2006 as well as many exhibits, classes, and public lectures on the UC Berkeley Campus.

Research Accomplishments

Chapter III 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.

The M6.5 San Simeon earthquake of 12/22/03 was an ideal opportunity to demonstrate the power of several approaches that have been pioneered at BSL over the last few years. The finite source modeling technique, developed by Dreger and his students to obtain directivity information for large regional earthquakes using a sparse set of regional distance broadband stations, provides information on the regional distribution of shaking, as well as on the the source process. The corresponding algorithm was implemented into the BSL real time analysis system two years ago, just in time to capture the San Simeon earthquake (III.13) for which it provided significant information, since this event occurred in an area poorly covered by seismic, and particularly strong motion, stations. The combination of seismic and geodetic constraints, another approach in which BSL is a leader, provided a robust model for the corresponding slip distribution on the causative fault, confirming the marked south east progression of the rupture (III.14). BSL researchers continue to study regional earthquakes and volcanic processes using broadband seismic data (III.15, III.17), microseismicity using data from our borehole networks (III.12, III.16), as well as regional deformation in California (III.19, III.22) and elsewhere in the world (III.20, III.21, III.23, III.24) using GPS and InSAR data.

We note an increasing interest in the study of seismic background noise, which, it turns out, contains valuable information on 3D shallow structure, such as that of sedimentary basins (III.25). At low frequencies, a fascinating component of the background noise is the Earth's "hum", discovered 6 years ago by Japanese scientists. A highlight of this past year's work at BSL is the development of an array-based method that has allowed us to locate the primary source of the "hum" in the oceans. This main source moves from the northern oceans in the northern hemisphere winter to the southern oceans in the summer, as wind-generated waves grow stronger in the winter in the respective hemispheres. This study has been published in Nature and received considerable media attention (III.26). The existence of the BDSN which its regional distribution of very broadband STS-1 seismometers in high quality installations has been instrumental in this study. Indeed, BDSN is one of only two such suitable regional arrays in the world for which data have been continuously available for several years (the other one is in Japan). Data from our ocean floor MOBB station in Monterey Bay are also proving valuable, in conjunction with ocean buoy data, to investigate how short period ocean wave energy is converted into long period elastic waves (III.18). Another area where "digging into the noise" has proven useful, is the discovery by Japanese and Canadian scientists of deep strain events along subduction zones manifested by signals in GPS associated with seismic tremors. Such signals appear to be present also in California, at the southern end of the northwest Pacific subduction zone (III.27).

In the last year, we have sustained our investigations of global earth structure. Notably, we developed the first whole mantle radially anisotropic model, showing, in particular, the predominance of horizontal shear in the D" region near the core-mantle boundary, a study published in Science (III.28). The anisotropic formalism developed over the last few years is being extended to more detailed studies at the continental scale, with the inclusion of azimuthal anisotropy (III.29). Concurrently, we continue our efforts in the modeling of wave propagation in 3D structure at the global scale, using numerical and analytical approaches (III.32, III.31, III.30). We also maintain an active program in the study of inner core structure, this year documenting the presence of large scale lateral variations in temperature at the top of the inner core (III.33).

I am happy to announce the completion of two Ph.D theses in this past year: Matt d'Alessio has started a Mendenthal Postdoctoral fellowship at the USGS in Menlo Park, CA, while Mark Panning will stay as a post-doc at BSL for the next year. In the summer of 2003, post-doc and former student Yuancheng Gung returned to Taiwan where he joined the faculty at the National University of Taiwan, while visiting scientist Nozomu Takeuchi has returned to his post at the Earthquake Research Institute in Tokyo. Post-doc George Hilley will join the faculty at Stanford University in January 2005.

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 Christina Jordan and Eleanor Blair.

I also wish to specially thank the individuals who have regularly contributed 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, Bob Uhrhammer, and Stephane Zuzlewski. I particularly want to thank Doug Dreger for serving as Associate Director of the BSL.

To our regret, David Rapkin had to leave BSL in Fall of 2003. He now works for the Institute of Transportation Studies. André Basset and Wade Johnson left in the Spring of 2004 and, as employees of UNAVCO, they have joined the technical crews responsible for the deployment of PBO. We welcome the addition of Cédric de la Beaujardière, who joined the BSL staff in June 2004, assisting Mark Murray and Lind Gee in the data management and processing of BARD and BDSN data.

In 2003-2004, there have been some changes in the BSL administrative office. Eleanor Blair, Myriam Cotton and Christina Jordan continue to provide critical support to the administration of our lab. They have been assisted by part-time student employees Patty Villa and Loan Pham. In May 2004, Yolanda Andrade joined our staff as administrative assistant for the BSL

I also wish to thank our undergraduate assistants Charles Chiau, Alex Goines, Edwin Kwan, and Gabe Treves for their contributions to our research and operational activities.

As every year, I am particularly thankful to Lind Gee and Christina Jordan for their help in putting together this Annual Report.

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




Barbara Romanowicz

October 15, 2004

Berkeley Seismological Laboratory
215 McCone Hall, UC Berkeley, Berkeley, CA 94720-4760
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