Operation of a telemetered seismic network on the Alaska Peninsula. Annual report

• Main Author: Not Available
• Language: unknown
• Published: 2013
• Subjects: 58 GEOSCIENCES; ALASKA; SEISMICITY; ALEUTIAN ISLANDS; CONTINENTAL SHELF; EARTHQUAKES; RESEARCH PROGRAMS; SEISMIC ARRAYS; SEISMIC DETECTION; VOLCANOES; CONTINENTAL MARGIN; DETECTION; ISLANDS; MEASURING INSTRUMENTS; NORTH AMERICA; PACIFIC NORTHWEST REGION; SEISMIC EVENTS; USA; Pacific; Kodiak; Alaska; Aleutian Islands
• Online Access: http://www.osti.gov/servlets/purl/6526012; https://www.osti.gov/biblio/6526012; https://doi.org/10.2172/6526012

A large aperture network of eleven short period seismic stations is being operated on the Alaska Peninsula and several offshore islands to acquire data for the study of the seismotectonics of a part of the Alaska-Aleutian arc-trench structure. The system operated satisfactorily during the past year and continued to provide seismic coverage at a low magnitude threshold level (M/sub L/ = 2.0). An event detection system, developed under this contract over the past years, has been field installed and is undergoing fine tuning. Focal mechanism studies of intermediate depths Benioff zone earthquakes were continued. Like a previous, smaller set, these mechanisms show predominantly down-dip extension, indicating gravitational sinking of the subducting lithosphere. Analysis of the combined data from our network and a temporary array of Ocean Bottom Seismometers, deployed under a related study, indicate that epicenters of earthquakes in the continental shelf area off Kodiak Island are shifted landward by about 15 km with respect to the epicenters determined from the combined data set. Clusters of shallow seismic activity associated with certain Alaska Peninsula volcanoes, observed over the past years, had previously been interpreted as related to shallow magmatic-geothermal reservoirs. Volcanologic-petrologic field studies conducted last year show that volcanic centers associated with such swarms do indeed have surface manifestations of hydrothermal activity.