Double-difference location and ground-truth classification of the 2008 Mogul, Nevada, very shallow earthquake sequence

• Autores: David von Seggern, John G. Anderson, Ileana Tibuleac, Glen Biasi
• Localización: Seismological Research Letters, ISSN 0895-0695, ISSN-e 1938-2057, Vol. 86, Nº. 1, 2015, págs. 146-157
• Idioma: inglés
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• Resumen

  • A long sequence of shallow earthquakes occurred west of Reno, Nevada during 2008 beneath a community called Mogul (Anderson et al., 2009; Tibuleac et al., 2011). This sequence began with a swarmlike series in early 2008 and was punctuated by an Mw 5.0 earthquake on 26 April 2008. (06:40:10 UTC and 10:40:10 p.m. 25 April local time). The mainshock was followed by a fairly typical aftershock sequence through the remainder of 2008. The sequence consisted of over 2000 earthquakes with ML=1.0, concentrated in depths between 1 and 4 km and ranging in magnitude up to Mw 5.0 (mainshock). The swarmlike activity prior to the mainshock provided time to instrument the epicentral area with temporary broadband and strong-motion stations, in advance of the occurrence of the largest events. These stations complemented the Nevada and California permanent seismic monitoring stations and the high-quality broadband stations of the Earthscope Transportable Array network deployed in Nevada during 2008.

    The primary objective of this study was a detailed investigation of this sequence of earthquakes in terms of location and ground-truth (GT) classification. Compared with earthquakes at typical depths, these shallow earthquakes have near-field ground motions with uncharacteristically high amplitudes and rapid attenuation with distance (Anderson et al., 2009). For our investigations, we used a unique broadband and strong-motion recording database, obtained from stations as close as 1 km from the epicenter of the mainshock and most of the smaller events. These sensors recorded waveforms that we have organized into a database including near-field and seismic-network recordings of all the ML=1.0 earthquakes of the sequence located by the Nevada Seismological Laboratory (NSL). We have relocated the Mogul earthquakes with hypoDD, incorporating P and S cross correlations. Location shifts as large as several hundred meters were observed when compared with the original catalog...