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Tensor Strain in California for NEHRP |
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Tensor Strain for NSF’s PBO |
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The PBO project aimed to install 100+ GTSM instruments across the North Western region of the United States (only approximately 80 of the 107 systems supplied by GTSM were actually installed within the funding budget and timeframe). This area will provide a useful of information due to a great deal of tectonic activity. The region has extensive GPS and seismic coverage and many different tectonic target types.
The Google map to the right shows the installations in 2005 and early 2006. For a large scale image showing all of the current sites, go to the Location Map.
For complete site listings, visit UNAVCO for the Plate Boundary Observatory program of Earthscope, the major Research Equipment initiative (2004) of NSF.
New Videos to Unavco installations available: Overview of Anza Cluster and Hoko Falls Installation
GTSM is not directly involved in provision of the data from this array or in its maintenance which UNAVCO performs. The complete data archive is publicly available through the UNAVCO web site. GTSM provides on its home page an easy to use data download from this public archive for the convenience of users, and some highlights of the early data.
AUGUST SEPTEMBER 2005 A Cascadia silent slip event was expected late in August 2005. this event was observed at P403 and Hoko (B004) sites, see Location Map of sites. The event initially propagated through P403 in late August, and a second cycle was observed to begin at the HOKO strainmeter site around September 9. The total duration recorded to September 15 being about 18 days. Examples from the record are shown below.
JUNE 2005 An early start to a new era of PBO/GTSM borehole strain meters. With the grout only five hours old we had our first event in Northern California, the M7.2 of 02:50:54 on June 15, 2005, located 140 km west south west of Cresent City.
High frequency (20Hz) data was captured during this event. Obviously the data are recorded through very incompletely set grout with very low modulus. The figures are raw single component data with a nominal calibration of 0.1 nanostrain per count. Peak amplitudes are about 30 nanostrain. The beginning of the arrival on a 10 minute time scale is shown at figure 1 and figure 2 shows the subsequent ten minutes of the event as seen at HOKO. The three channels show are at azimuths 120 degrees apart. The record is equally interesting on the fourth channel. |
