Infrasound Monitoring of Local, Regional and Global Events

摘要

Methodologies for the detection, association, location and identification of infrasound sources at local, regional and global distances are discussed. In the first part of this paper we apply a new regional monitoring method to data from the Washington State seismo-acoustic network and identify 206 local and regional infrasonic events in a dataset comprising 28 days of data. We detect multiple signals from mining explosions at two sites in Washington State, including 5 events that were recorded in a regional seismic bulletin. We also automatically detect and associate signals from the March 9th 2005 eruption at Mount Saint Helens, and locate the event to be within 5 km of the caldera. The second part of this paper outlines a technique for identifying infrasound signals from large known events on a global scale. We apply the technique to data from International Monitoring System (IMS) infrasound arrays for three super-bolides occurring on September 3rd, 2004, over Antarctica; on October 7th, 2004, over the Indian Ocean; and on December 9th, 2006, over North Africa. For each bolide we observe signals at multiple infrasonic arrays, with observations at ranges from tilde 1,000 to tilde 13,000 km. We investigate the causes of the asymmetric distributions of observations and show that site-noise is a dominant effect up to a range of tilde 10,000 km. We discuss how the preliminary work outlined in this paper provides important constraints for the purpose of event identification at local, regional and global distances. For large events, we outline how the synthesis of local, regional and global infrasonic data would provide the optimum dataset for event location and identification.