Seismo-Acoustic Generation by Earthquakes and Explosions and Near-Regional Propagation

Seismo-acoustic measurements provide an opportunity to quantify natural and man-made sources that are at or near the Earth's surface. We have operated three acoustic arrays collocated with seismometers from the University of Utah Seismograph Stations (BGU, EPU, NOQ). We report on progress in three separate areas of research related to these seismo-acoustic databases. The first topic investigates seismo-acoustic signals from the Wells, Nevada earthquake that occurred on February 21, 2008 at 14:16:02 UTC (Mw 6.0). The detailed research and interpretation of this event has been conducted under a separate effort (Arrowsmith et al., 2009c, these Proceedings). The focus in this work is on the data acquisition and highlighting the sources of seismo-acoustic signals that can be observed on regional seismo-acoustic arrays. This event was well recorded by many seismic stations, including the EarthScope Transportable Array (TA) stations, and was also recorded by three infrasonic arrays in Utah (BGU, EPU, NOQ), one in Nevada (NVIAR), and one in Wyoming (PD1AR). The waveforms recorded from the Wells sequence (main event and aftershocks) at the five infrasonic arrays are characterized by complex signals that correspond to: (1) P and 5 arrivals, a result of the coupling-to-air of the seismic waves that traveled to the vicinity of the infrasonic stations (local infrasound); (2) a secondary source of infrasound between the source and receiver; and (3) epicentral infrasound (acoustic energy that was generated by the ground motion at the epicenter and traveled through the atmosphere to the arrays at air sound speed). The second area of work focuses on characterizing acoustic to seismic coupling. In August 2007, infrasound microphones were added at Earthscope stations PI3A, M13A, M14A, and N12A as part of an experiment to record 40,000 lb explosions at the Utah Test and Training Range on Hill Air Force Base (AFB).
Prepared in collaboration with University of Utah Seismograph Stations, Korea Institute of Geoscience and Mineral Resources, and Los Alamos National Laboratory. Proposal no. BAA08-65. Presented at Monitoring Research Review - Ground-Based Nuclear Explosion Monitoring Technologies, MRR 2009, Tuscon, AZ on 21-23 Sep 2009; published in proceedings of the same, v1 p230-238. The original document contains color images. All DTIC reproductions will be in black and white.