Introduction

Two moderate size (mb = 5.8, 6.0) earthquakes and their aftershocks that occurred within the Shumagin Islands seismic network in Alaska have produced a unique data set for a detailed study of convergent tectonics at depth in an area that has been identified as a seismic gap [Kelleher et al., 1970].

Lamont-Doherty Geological Observatory has operated a network of vertical short-period, radio-telemetered station in the Shumagin Islands region of Alaska since July 1973 [Davies and House, 1979]. As originally installed, the network consisted of eight high-gain remote stations that telemeter their data to a central recording site at Sand Point (Figure 1). Fig. 1