Studies of Unusual Earthquakes: Volcanos and Landslides

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The project involves the investigation of anomalous seismic sources with a specific focus on slow earthquakes associated with volcanos and landslides. It builds on results and discoveries that have come from the systematic application of a long-period event detection algorithm to real-time and archive seismic data recorded on the Global Seismographic Network. For each year since 1991, more than 100 earthquakes of magnitude 5 or greater that are not reported in other catalogs have been detected and located using this algorithm. Many of these earthquakes are slow, and a large number of them have been associated with volcanos and landslides. The first goal of the project is to discriminate volcano and landslide earthquakes from other earthquakes that have been identified only by the long-period detection algorithm. The second goal is to relate those earthquakes that occur in volcanic regions to eruptive activity and changes in the geometry and behavior of magmatic plumbing systems. In particular, the project will involve a detailed comparative study of unusual earthquakes associated with the two greatest caldera collapses of basaltic volcanos over the last century, Fernandina (Galapagos Islands) and Miyakejima (Japan). The third goal is to investigate anomalous earthquakes associated with large landslide events. A recently developed methodology for determining the trajectory of the sliding mass during a landslide directly from the radiated seismic waves will be refined and improved and applied to several known and inferred landslide events in order to estimate dynamic landslide parameters.The project will lead to an improved characterization and discrimination of earthquake sources, and will help clarify the phenomenology of volcano and landslide earthquakes. The volcano investigations will provide new constraints on stress and deformation patterns within active volcanoes, as well as on the mechanics of caldera collapse and its relationship to magmatic transport and plumbing. The landslide investigations will lead to better characterization of the seismic radiation from landslide sources, and will provide new constraints on key landslide parameters, such as mass, runout, and effective coefficient of friction. The seismological analysis methods developed for these studies will contribute to improved monitoring capabilities for volcanos and landslides, which represent important classes of geohazards.