Waveform correlation detection methods applied to the 2003-2004 seismic swarm in the Marysvale volcanic province of Central Utah

Earthquake swarms are defined as clusters of events that occur closely in space and time without the presence of an outstanding main shock. Swarms are especially common within the seismically active region of the Intermountain West, monitored by the University of Utah Seismograph Stations (UUSS). The source mechanism of swarms is not well understood, although previous work suggests that they are sometimes induced by the propagation of hydrothermal or magmatic fluids. To better understand the spatial and temporal characteristics of seismic swarms in Utah, waveform correlation methods were used to detect small events in a swarm sequence that were missed in routine UUSS earthquake cataloging. The main sequence of the analyzed swarm lasted from 29 Nov through 4 Dec 2003, and occurred near the Marysvale volcanic province in central Utah. Utilizing nine single-component and two three-component UUSS short-period seismic stations, at distances of 29161 km from the swarm source, a single waveform template detector was run against continuous seismic data from 20032004. This method detected 453 new events, increasing the original UUSS catalog of 36 swarm events by a factor of about 13. A total of 126 of these detections were detected at four or more stations and are likely to be locatable. The single template method was tested for robustness by comparing results from multiple single event templates and by comparing the single event template to a stack template and a two-dimensional empirical subspace. Within the uncertainty bounds, no technique was superior when applied to all the stations.