High-precision Earthquake Location and the Internal Structure of Active Volcanic Systems

University Of Wisconsin-Madison, Madison WI

Investigators

Abstract

EAR-0001138 Clifford H. Thurber In most instances, the seismicity associated with magmatic activity (eruptions or intrusions) has apppeared rather diffuse, suggesting that the activity may surround the zone of a conduit or propagating dike. A radically different view of the relationship between seismic activity and propagating magma for Kilauea's East Rift Zone has been put forward by Gillard et al. [1996] and Rubin et al. [1998]. By combining the results of high-precision earthquake location (HPEL) with theory and mechanical modeling, these authors conclude that the observed seismicity is concentrated in pencil-thin features near the top edge of a deep magma body underlying Kilauea's East Rift. This localization is due to the stress concentration at the upper edge of the weak magma-rich zone. These results emphasize the value of applying HPEL to digital seismic data from volcanic systems, and also point to a potential new way of identifying dikes and magma bodies using seismicity patterns. The PI's work so far studying seismicity at several volcanic systems has resulted in the clarification of seismicity within two large volcanoes, Mount Pinatubo and Mauna Loa. In each case, two separate but diffuse clusters of seismicity become well-defined features after relocation analysis. This project will continue and expand this work to include several other active systems. Some key aspects of the project are the use of state-of-the-art techniques for arrival-time determination and earthquake location and the access to several unique, high-quality data sets from volcanic systems around the world.