A high-Resolution Seismic Array Experiment in the Hualien Area, Taiwan A high-Resolution Seismic Array Experiment in the Hualien Area, Taiwan

Abstract

A high-resolution seismic array experiment using a 30-station second generation of Portable Array for Numerical Data Acquisition (PANDA II) array was deployed in the Hualien area, Taiwan from late July 1993 to September 1995. This array covered an area of roughly 60 km x 30 km extending from an oceanic crust (the Coastal Range) across a suture zone (the Longitudinal Valley) into a continental crust (the Central Range) with 5- to 10- km interstation spacing. Each station was equipped with a 2-Hz three-component seismometer and had four channels with three data channels and one gain channel. This experiment making use of the PANDA II system was the first of its king in the world. The PANDA II is a second generation of PANDA with major improvements in its dynamic range and telemetry scheme. It has a maximum of 132 dB dynamic range by using a five-step gain ranging system (18 dB each). Seismic signals and gain information were telemetered yb radio to a recording center where two PC-486 computers were used for on-line digital data acquisition and off-line data analysis. More than 1600 local and regional earthquakes whith magnitudes up to 6.2 were recorded on-scale in the first five months. This experiment shows that both the monitoring capability and the locating reliability of earthquakes by the PANDA II array are better than those by the regional seismic network. This indicates that the PANDA II system is a better seismographic system for studying seismicity tand related tectonics in great detail. The experiment also reveals that seismicity in the Hualien area is characterized by an abundance of shallow crustal earthquakes.

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