As usual, our research activities of the last year span a vast range of topics, from regional, earthquake related problems to global investigations of earth's deep structure all the way down to the inner core. Part 3 is devoted to individual reports on the status of our various research projects.
The "regionally focused" research is closely linked to our mission to provide, on the one hand, education, and on the other, timely and accurate information, about earthquakes that occur in central and northern California. Regarding the education aspect, we describe in Section 8 our outreach program, highlighted this past year with our participation in the Interactive University Project. The information aspect depends heavily on the data which we acquire from our various regional geophysical networks. Because this represents such a central part of our activities, I summarize below the main accomplishements in this area during the last year.
In 1997-1998, our efforts have continued to consolidate and expand our core instrumentation programs, the Berkeley Digital Seismic Network (BDSN), the Hayward Fault Network (HFN) and the Bay Area Regional Deformation Network (BARD).
One new BDSN site has been installed at the Carmenet Winery in Sonoma Valley and two other sites in the east of the Bay Area (Black Diamond Mines and Potrero Hills) are nearing completion and will be operational by the end of 1998, at which point the network will count 20 very broadband and strong motion stations. Concurrently, we have explored and found new sites to relocate our noisiest stations, MIN and ARC. Much effort has gone, as usual, to improve the quality of our sites by systematically monitoring background noise and investigating means to reduce it, as well as trying to minimize failures occasioned by ligthning and flooding. Notably, during the past year, all 7 stations equipped with STS-1 seismometers have been upgraded to "warpless" baseplates, which allow the low frequency tilt effects due to atmospheric pressure to be reduced on the horizontal components. You will find, in this report, a detailed account of our site selection and installation procedures. Thirteen of our sites are now recording auxiliary pressure and temperature channels and two sites (SAO and PKD1) have colocated 5 component electro-magnetic sensors, from which data are being processed in an attempt to extract possible tectonic signals.
Another important development has been the upgrade of the BDSN Quanterra dataloggers to full ethernet connectivity, which, in particular, allows us to send the data from individual stations to multiple recipients. This is particularly important for the purpose of establishing a redundant data processing center for our real-time data analysis and broadcasting program (REDI), outside of the San Francisco Bay Area. Being able to stay "on-line" in the case of a large earthquake in our backyard is, of course, one of our primary concerns. With seed funding from the OES, we have established the core of such a center at the OES headquarters in Sacramento, where a computer duplicating our real-time procedure has been installed and frame-relay connections to 6 of our BDSN stations have been established. This system will be coming on-line this Fall. We hope that funding will be available in the near future to connect our entire network to this back-up site. We are also continuing research towards the development of algorithms that will allow us to take full advantage of the broadband character of our instruments, in order to determine the primary source parameters of significant earthquakes (location, magnitude, source mechanism, directivity..) based on a sparse network. Such a capability has significance not only for redundancy purposes in the Bay Area, but also in the event of a large earthquake occurring outside of the most densely populated zones, which are currently the focus of efforts to densify the distribution of strong-motion instrumentation.
The Berkeley component of the high resolution borehole Hayward Fault Network (HFN), from which data are incorporated in the real time REDI system, has grown by one station in the past year (Saint Mary's college, SMCB), increasing the coverage on the north-east side of the Bay. The southern Hayward Fault portion of this network is being deployed and operated by the USGS at Menlo Park. Much effort has gone in 1997-98 at the BSL to refine and test a central detector system at UC Berkeley, that will allow the retrieval of event data at very high sampling rate (500Hz) in addition to the current acquisition of continuous data at 100Hz, and will allow the detailed study of micro-earthquakes (down to magnitude zero) along the Hayward Fault similarly to what is being done with Parkfield data (see section on Parkfield data analysis). The central detector system has now been running in test mode for over a year and will soon come on-line. The development of the northern portion of the HFN is closely linked with the Bridge Safety Project of the California Transportation Department, which has made possible the installation of sensor packages in 15 bedrock boreholes at 5 east-Bay bridges in collaboration with LLNL. Efforts to link these stations by real-time telemetry to UC Berkeley are under way.
BARD has grown by 4 new UCB sites in the Bay Area in 1997-98, while 7 additional sites are under construction, including 1 in cooperation with LLNL, 1 in cooperation with UC Santa Cruz, and three UC Davis sites which will be maintained and operated by the BSL. With these sites, we are seeing the completion of the instrumentation deployment made possible with partial support from an NSF MRI grant coordinated through UNAVCO to improve the coverage of western US with permanent GPS stations for the purpose of tectonic deformation studies. With all of the BSL-operated stations now linked to UCB by continuous telemetry (notably piggy-backing on the frame-relay telemetry of the BDSN), we are continuing to develop capabilities for quasi-real time analysis of GPS data in complement to seismic data, for the purpose of constraining rupture parameters in the event of a large earthquake.
The saturation problems of the Northern California Earthquake Data Center (NCEDC) have been happily resolved with the help of a grant from the USGS, which has allowed us, with matched funds from the BSL, to purchase and install a new mass-store device ("juke-box"), whose current capacity of 1.2Terrabytes will hopefully be expanded to 5Terrabytes within the next few years. A focus of our efforts in 1997-98 has been the development of a database system, in collaboration with the USGS and Caltech, to more efficiently store the earthquake related parametric data archived at the NCEDC. In particular, the BSL and the USGS have spent considerable effort in the past year to construct a single northern California earthquake catalog by merging independent catalogs maintained since 1967 by both institutions.
It is clear that the future of our instrumentation program is now closely linked to collaborative efforts with other institutions, to develop a fully integrated joint monitoring system for northern California. At BSL, we are fully committed to such an effort, which, beyond the current UCB/USGS joint notification system, involves densification of the strong-motion sites in the San Francisco Bay Area (as goal of on the order of 500 sites), and the development of a robust and redundant data exchange and processing system between the three primary institutions: the California Division of Mines and Geology strong motion instrumentation program (CDMG/SMIP), UC Berkeley and the US Geological Survey. A significant component of this effort will be the production of "shakemaps" immediately after the occurrence of a significant earthquake. To initiate this effort, temporarily referred to as "TriNET North", in reference to a similar, already funded effort in southern California, a Memorandum of Understanding between the 3 institutions (see Appendix) has been signed in June 1998. We expect this program to be a significant focus of ours in 1998-99. We are also engaged in collaborative efforts with other institutions to raise funds for the densification of deformation monitoring in the Bay Area (GPS and strainmeters). Last but not least, we are taking an active part in the developments of a plan for the California Earthquake Research Center (CERC) which is currently being considered for funding within the NSF-Science and Technology Center program.
Finally, we have obtained matching funds from the NSF to upgrade our SUN computer network, and also to upgrade to 100Mbit capacity the ethernet network which forms the backbone support of computationally intensive research, both for the BSL staff and the Geophysics faculty and visitors in the Department of Geology and Geophysics. Unfortunately, the installation of this network must await the completion of the McCone renovation project and our move to the 2nd floor of McCone Hall, which has been considerably delayed. This renovation project has also required that we move part of our operations to Wellman trailers 200 yards west (and down) from our headquarters, creating many logistical problems and slowing down our progress. We await impatiently the successful completion of this project.
I wish to thank the scientists, technical and administrative staff and students of the Berkeley Seismological Laboratory for their contributions which reflect this past year's efforts, and particularly thank them for adapting to the new format of this annual report, which, for many, meant learning all about latex, and encountering frustrations with getting figures and tables in proper form. Finally, let me note that two of our former graduate students have moved on, in the Spring of 1998, to post-doctoral positions, Mike Antolik at Harvard and Mike Pasyanos at LLNL, and three of our post-docs have left the BSL in the summer of 1998 for jobs at the University of Paris, France (Eric Clevede), the Ecole Normale Superieure in Lyon, France (Daphne-Anne Griot), and the Stanford Research Institute (Joe Durek). I wish good luck to all of them, as well as to Raphaelle Millot, who visited us for 6 months from ENS in Paris in the Spring 1998 and is now starting graduate school at the Institut de Physique du Globe in Paris.
September 20, 1998