Stanford - USGS Ultra-Low Frequency Electromagnetic Network: Status Report and Data Availability Via the Web
Abstract
As part of the PBO (Plate Boundary Observatory) mission we have installed three ultra-low frequency electromagnetic (ULF-EM) recording sites in northern California. We hope to use this data to better understand physical processes associated with earthquakes and to find evidence for the generation of subsurface electromagnetic fields, including the presence or absence of pre-seismic transients. Our ULF-EM sites complement two existing sites maintained by UC Berkeley at Parkfield and Hollister in central California and a growing California network of magnetometers managed by Quakefinder, Inc. (www.quakefinder.com). We installed our first station in 2005 close to the Stanford University campus. In 2006, we completed two additional installations in the North Bay and East Bay. Each site has three orthogonal magnetometers and duplicate sets of orthogonal horizontal electrode pairs, recording signals from 0.001 to 20 Hz, collocated with an existing broadband seismometer. All data are archived at UC Berkeley's Northern California Earthquake Data Center (NCEDC). We have created a website, http://ulfem-data.stanford.edu/, that collects and stores ULF-EM data from our stations. Users can request data plots on the website and view them immediately or after a few minutes, depending on whether or not the information is more than a year old. Currently we can display time-series data on demand from all our stations, with data available 30 minutes after acquisition. In the near-future we will be able to provide spectrograms on demand, and ultimately a range of user-selected transfer functions computed for chosen time periods. 2009 efforts will focus on expanding our network of ULF-EM stations, by installing the first of several new stations, and upgrading primary remote reference stations. Each site will include state-of-the-art magnetic and electric sensors sensitive from 0.001-100 Hz, and data will be fed to the NCEDC. The first phase of this work, which has already begun, involves upgrading twenty-year-old reference stations at Hollister (SAO) and Parkfield (PKD) that provide a necessary reference critical to the general interpretation of EM data from the current Bay Area stations that are located in electromagnetically noisy environments. Part of this upgrade involves the deployment of newly developed electrical-signal conditioning systems for the EM sensors, improved system isolation, and revised power supply and signal digitizers. Later in the year we will install the first of several new stations. In addition to the three present Bay Area stations and two remote reference stations, the network will include two clusters of three ULF-EM stations, centered near the town of Hollister (roughly 70 km south of San Jose) and in the North Bay along the Rodger's Creek Fault, that will be installed over the next three years.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2008
- Bibcode:
- 2008AGUFM.S53B1824N
- Keywords:
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- 0530 Data presentation and visualization;
- 7223 Earthquake interaction;
- forecasting;
- and prediction (1217;
- 1242)