New Mexico Geological Society Annual Spring Meeting
April 7, 2017

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Using a New Temporary Seismic Network to Detect Earthquakes in the Socorro Magma Body Region

Rhiannon E Vieceli1, Susan L Bilek1, Richard C Aster2, Lindsay Lowe-Worthington3 and Brandon Schmandt3

1New Mexico Institute of Mining and Technology, Socorro, NM, 87801,
2Colorado State University, CO
3University of New Mexico, Albuquerque, NM, 87131

The Socorro Magma Body (SMB), a thin tabular shaped body of magma located at a depth of 19 km within the Rio Grande Rift in central New Mexico, is the second largest continental mid-crustal magma body in the world. This feature leads to slow regional uplift on the order of a few mm/yr and has been linked to concentrated seismicity at shallower depth. These small earthquakes have been monitored with a variety of long- and short-term local seismic networks over the past several decades, although with large station spacing, limiting resolution. For two weeks during February 2015, seven broadband and 804 vertical component short period node seismographs were deployed with a station spacing of approximately 300 m in the northern region of the SMB, where uplift is maximum. This temporary installation of instruments has been the largest of its kind in the region. Initial, visual review of the broadband data produced a catalog of 33 small magnitude earthquakes located within the region. Additional events may be recorded in the collected seismic data, but evade visual identification due to lower signal-to-noise ratios (SNRs). Implementing cross-correlation techniques has proven useful in identifying signals even when the SNR is relatively low. Cross correlation is a measure of similarity between two waveforms as a function of a time lag applied to either of the waveforms. Identification of events using cross correlation starts with a high-quality recording of an earthquake signal of interest, known as a template. The template signal is then correlated with the continuous seismic data stream over a time range of interest to detect signals with a similar shape. Here we use the initial earthquake catalog as templates in a cross-correlation scanner to detect additional events recorded on both the broadband and more numerous node seismographs. We also will compare the newly detected events with detections produced by a back-projection technique using the node data. Our newly detected events will be located using a regionally appropriate velocity model for comparison to longer term earthquake catalogs and regional structure of the SMB.

pp. 71

2017 New Mexico Geological Society Annual Spring Meeting
April 7, 2017, Macey Center, New Mexico Tech campus, Socorro, NM