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IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS003 Oral Presentation 1857 Recent Progress in Infrasonic Early Warning Systems Dr. Milton Garces Infrasound Laboratory University of Hawaii, Manoa IAVCEI David Fee, Michael Hedlin, Robin Matoza, Hugo Yepes, David Mccormack, Rene Servranckx, Henry Bass The emerging global infrasound network has stimulated a growing number of infrasound projects devoted to natural hazard applications. These applications include monitoring volcanic eruptions, extreme weather, large ocean swells, bolides and tsunamis. The Acoustic Surveillance for Hazardous Eruptions (ASHE) project aims to develop and evaluate the capability to use low frequency sound to provide robust, low-latency notifications of volcanic eruptions over regional distances. We describe current field deployments of several small, autonomous infrasound arrays in Washington state (US) and Ecuador. The arrays in Washington have detected diverse eruption signals from Mount St. Helens, and the arrays in Ecuadorhave captured eruptions from Tungurahua and Sangay Volcanoes, as well as Galeras in Ecuador. These stations send continuous real time data to a central facility where automatic analysis techniques for eruption detection are being prototyped. Plans are in place to send automated notification products on a test basis to a participating ICAO-designated Volcanic Ash Advisory Center for comparison and possible integration with their existing warning systems. Keywords: infrasound, volcanoes, ashe

IUGG XXIV General Assembly July 2-13, 2007 Perugia, Italy (S) - IASPEI - International Association of Seismology and Physics of the Earth's Interior JSS003 Oral Presentation 1858 Real-time, probabilistic and evolutionary earthquake location for seismic early warning Dr. Claudio Satriano RISSC-Lab AMRA Scarl Anthony Lomax, Aldo Zollo An effective early warning system must provide probabilistic estimates of the location and size of a potentially destructive earthquake within a few seconds after the event is first detected.In this work we present an evolutionary, real-time location technique, based on a robust, equal differential time (EDT) misfit function, a very fast, global-search algorithm, and a probabilistic approach for describing the hypocenter estimation. The location technique, at each time step, relies on the combined information from triggered arrivals and not-yet-triggered stations. With just one recorded arrival, the hypocentral location is constrained to be within the Voronoi volume around the first triggering station. The Voronoi volume is defined by the current time and the travel times to the not-yet-triggered stations; this volume shrinks as time passes, event if no new arrivals become available. With two or more triggered arrivals, the location is constrained by the intersection of the Voronoi volume defined by the remaining, not-yettriggered stations with the EDT surfaces for all pairs of triggered arrivals. (At each point on an EDT surface the difference in the predicted travel times to two stations equates the difference in the observed arrival times at the two stations.) As time passes and more triggers become available, the evolutionary location converges to a standard EDT location.We show several tests of the real-time location technique using arrivals generated by different automatic picking procedures for strong-motion data from moderate to large earthquakes worldwide. The results indicate that useful, probabilistic location estimates, suitable for early-warning applications, can be achieved with very few recording stations (1-2), while, in comparison, a standard location algorithm usually needs 3 or more stations to begin constraining the hypocenter.We also present an event binding procedure for the real-time location technique to detect multiple sources and associate phase arrivals when different events occur close in time. Keywords: location, evolutionary, probabilistic

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