Facilities - Seismic Observatories
Data Centers
NEES Data Center
The NEES@UCSB data center, maintained at ERI, receives data streams from several ultra low power remote field sites (more information in the NEES section below). These sites, equipped with seismic monitoring sensors, water-table pressure monitoring sensors and video telepresence cameras, deliver their data via VPN routers connecting the radio-based wireless field network to the local ERI network servers. The ERI data center servers provide researchers real time access to the streaming data as well as forward the data to other national data centers.
Consortium of Organizations for Strong-Motion Observation Systems (COSMOS) Data Center
The COSMOS Virtual Data Center (VDC) is an unrestricted web-based search engine for access to worldwide earthquake strong-motion data. It provides an interactive resource for research and practicing earthquake engineers, Earth scientists, and government and emergency response professionals. VDC users have a wide range of access options; they may search on specific characteristics of the data, view data in a geographical perspective, preview records, compare recorded data with design spectra and retrieve the data and metadata of most interest to them.
The data available through the Virtual Data Center (VDC) now includes 515 earthquakes. 3108 stations, and 26,563 accelerogram traces. These station records all include acceleration, and most include velocity, displacement and spectra files, as well as metadata about site geology and instrumentation.
The VDC is affiliated with COSMOS, the Consortium of Organizations for Strong-Motion Observation Systems, a public-interest nonprofit corporation of federal and state agencies, universities and private companies. COSMOS' mission is to expand and significantly modernize the acquisition and application of strong-motion data in order to increase public safety from earthquakes. The VDC is supported by funds from the USGS the Department of the Interior, the Army Corp of Engineers, and the California Geological Survey (CGS); and COSMOS also provides a working group which oversees the operation and development of the VDC.
Instrumentation and Seismic Observatories Programs at ERI
ERI is home to significant instrumentation and research efforts focused on understanding the physics of the earthquake process and the effects of earthquakes on the built environment. These require not only computational facilities for doing theoretical modeling of wave propagation and earthquake source process simulation, but also field observatories for monitoring earthquake activity. These field observatories provide the control data for testing our theoretical models and simulation techniques in order to allow us to determine if our models are matching real observations of earthquakes.
ERI operates a number of field facilities for monitoring earthquakes. The cost of installing and operating both portable instrumentation and permanent field sites can be quite high, so these costs are shared by many funding agencies. Currently, the largest field monitoring program at ERI is supported through the National Science Foundation (NSF) Engineering Directorate's George E. Brown Jr., Network for Earthquake Engineering Simulation (NEES) program. Support from NSF's Earth Sciences directorate and the U.S. Geological Survey through the Southern California Earthquake Center provide support for the Portable Broadband Instrument Center (PBIC) and the Borehole Instrumentation Program. These combined resources as well as some local institutional resources and in-kind support from other agencies are used to maintain the overall instrumentation and seismic observatories program at ERI.
Portable Broadband Instrument Center
Background
The Portable Broadband Instrument Center (PBIC) was established in 1991 by the Southern California Earthquake Center (SCEC) to provide researchers with year-round access to a "pool" of high-resolution, digital seismic recording equipment. The PBIC is managed out of ERI by Principal Investigator Jamie Steidl.
The data recorders maintained by the PBIC are primarily Refraction Technology (RefTek) 16 and 24 bit data acquisition systems (DAS's). Sensors consist of high output short period velocity transducers to record very small ground motion, force balance accelerometers designed to stay on-scale (up to +-2G) for the strong ground motion expected from very large earthquakes, and intermediate period weak motion sensors that provide increased frequency bandwidth to allow better investigation of deep basins and teleseismic or global earthquake monitoring. A broad dynamic range of recording is obtained by pairing both weak motion and strong motion sensors with a single recorder.
In the past two years the PBIC program has added two real-time capable 24 bit dataloggers and two low-noise strong motion accelerometers. The combination of these new dataloggers and sensors allows recording from as low as M1 earthquakes all the way to M8+ earthquakes on scale. In addition, these stations have the capability to stream the data continuously back to UCSB and the regional monitoring networks in real-time. The data is then integrated into the network processing routines, used for locating earthquakes, calculating magnitudes, and producing shake maps for emergency response for the larger events. Then the data is archived along with the permanent network data and made accessible through the regional data centers.
NEES@UCSB
The NEES @UCSB program, "Permanently Instrumented Field Sites for Soil-Foundation-Structure Interaction (SFSI)", one of 15 experimental earthquake engineering facilities in the U.S., is a 10-year operation to monitor earthquake activity at two field sites in Southern California as well as to facilitate active experimentation at these sites over the decade long program. The overall goal of the NEES program is to accelerate progress in earthquake engineering research and to improve the seismic design and performance of civil and mechanical infrastructure systems through the integration of people, ideas, and tools in a collaboratory environment. The NEES@UCSB field sites are integrated with the other 14 experimental facilities through central data and computational services via a unique IT infrastructure.
The overarching goal of the NEES@UCSB field site program is to improve on our ability to generate analytical and empirical models for accurate simulation of how the ground responds and deforms when shaken by earthquakes and to understand how this seismically induced shaking affects building structures and foundations. Two complimentary approaches have been developed: intensive monitoring of natural earthquakes with down-hole seismometers and pore pressure transducers, and the use of large "mobile shakers" to allow active shaking of both structures and the nearby ground during controlled experiments.
The Garner Valley NEES site:
Over the past two years, the original Garner Valley Downhole Array (GVDA) site has undergone a significant "face-lift" and expansion in scope with its integration into the NEES program. The Garner Valley downhole array (GVDA) project was originally installed under funding from the U.S. Nuclear Regulatory Commission in cooperation with the French Commissariat a l'Energie Atomique (CEA). The GVDA site was initially constructed to understand the effects of the near-surface soil conditions on seismic ground motion to improve ground motion prediction capabilities for design, seismic hazard assessment, and hazard mitigation. It was then expanded to understand the effect of earthquake ground motion on the hydraulic conductivity of ground water systems for the deep storage of nuclear waste. Now, with the complete integration into the NEES program the focus has expanded in scope to include issues like soil-foundation-structure interaction and liquefaction. A reconfigurable, steel-framed structure has been constructed at the GVDA site and instrumented with sensors in the structure, foundation, and underlying soil to monitor both earthquake activity and active shaking at the site.
The near-surface geological site conditions have been shown to be the dominant factor in controlling the amplitude and variation of strong ground motion, and the damage patterns that result from large earthquakes. This unique set of data collected from the Garner Valley project is used to advance the field of engineering seismology and geotechnical earthquake engineering. The site allows us to address problems such as how weak motion scales to strong motion, and how the recordings at different soil types scale to each other, especially with respect to a competent rock ("reference") site. The understanding of competing effects of amplification and attenuation including soil non-linearity and the extreme case of liquefaction is of a vital importance for seismic design studies. The site is located near the Anza segment of the seismically active San Jacinto fault in Southern California, which has a relatively high probability for a large earthquake of magnitude 6.5 or greater in the near future. The instrumentation and revitalization of the facilities at Garner Valley from the integration into the NSF NEES program provides a unique high quality data set that is the subject of many research studies.
The NEES Wildlife Liquefaction Array field site:
This site was developed under the NEES@UCSB program in the Imperial Valley of Southern California, just below the Salton Sea. It is located on California's Imperial Wildlife Management game refuge and was the site of an array installation in the early 1980's by the U.S. Geological Survey. This site was instrumented under the NEES program because of its history of significant ground shaking earthquakes in the region, six of which have generated liquefaction effects within 10 km of the site in the last 75 years. All of the pore pressure transducers installed in the early 1980's to monitor soil liquefaction behavior have since failed. The recent installation, located 65 meters down river from the previous site, is recording local earthquakes and also has been a test site for active shaking by one of the NEES mobile shakers. In addition, funding was obtained to re-instrument the old site and connect it in with the new site.
The location of this permanent field site within the highly active seismic region that includes the Southern end of the San Andreas Fault provides a wealth of data. In addition, this section of the fault system has not ruptured in over 300 years and is considered to be "overdue" so the site is well situated to capture the next "big one" on the San Andreas. As a supplement to the data from local earthquakes, active field tests like the one's conducted in previous years using the NEES mobile shaker "T-Rex" (operated by University of Texas at Austin), and planned experiments in the Salton Trough region in 2009 and 2010, are also helping to advance our goals of better understanding soil response and pore pressure generation during strong shaking.
UCSB Operated Observatories
In addition to the NEES facilities, two other engineering seismology array facilities donated to UCSB by the Japanese are currently operated using ERI resources. These arrays are very similar in scope to the NEES observatories. One is located in Southern California near Borrego Springs and the other is located in Central California, near the towns of Salinas and Hollister. These additional arrays provide greater chances for catching a big earthquake in close at a densely instrumented site as they are also located in seismically active areas.
The Borrego Valley Downhole Array:
In 1993, Kajima Engineering and Construction Corp. and Agbabian Associates established the Borrego Valley downhole array (BVDA) near Borrego Springs, in Southern California. In this array there are four borehole instruments extending depths of 9, 19, 139 and 238 m. In addition, BVDA has 15 surface instruments extending in two directions across the Borrego Valley, and a remote rock site at the edge of the valley that includes surface and borehole sensors. At the main station data acquisition systems building the shear wave velocity gently increases from about 300 m/s at the surface to 750 m/s at 230 m-the granite interface-where it jumps to 2500 m/s. The water table is at ~92 m; BVDA is representative of a dry site in NEHRP site class C.
The BVDA site is complementary to the NEES facilities in that it represents a different soil condition (dry vs. wet) and slightly stiffer material properties. It is important to collect data from all of the soil conditions encountered in the built environment in order to test our simulation methods using different soil models.
The Hollister Earthquake Observatory:
Agbabian Associates installed the Hollister Earthquake Observatory (HEO) in 1991 with funding from the Kajima Engineering and Construction Corporation. Kajima Corporation donated this array to the University of California, Santa Barbara in January 1998. It is located in the Salinas Valley where alluvium overlies Tertiary sandstone overlying Granitic basement. HEO has been operating since early 1992, and is located about 10 kilometers from the San Andreas Fault near the cities of Hollister and Salinas in central California. The ground motion array consists of a vertical array of six accelerometers in Quaternary alluvium, and three accelerometers installed at a remote rock station, 3 km to the Northeast. At the HEO main soil station accelerometers are located at 192, 110, 50, 20, 10, and 0 meters depth, going from crystalline rock at the bottom, up through consolidated and unconsolidated alluvium to the surface. Three sensor locations, surface Sandstone, surface Granite, and GL-53 meter borehole Granite are instrumented at the remote rock station. The location of HEO along the San Andreas Fault in Central/Northern California makes it an important addition to UCSB's engineering seismology field site programs.