The Array Analyzing of the High Quality Glacial Seismic Events Active in Greenland Using Long-Period Surface (Rayleigh) Wave Detection by the German Regional Seismic Network

Abstract

This study reports on four high quality glacial events in Greenland, M 4.9, 2007-07-04; M 4.8, 2007-07-09; M 4.7, 2007-07-09; M 4.7, 2007-07-20 detected using thelong-period surface waves (Rayleigh wave) recorded at the stations of the German RegionalSeismic Network (GRSN) array (German-GR and Geofon-GE programs). The waveformpatterns of the detected slow events for Greenland updated through 2008 were monitoredto analyze this new class of low-frequency earthquakes in the context of the array processingtechnique and array parameters using the software Seismic Handler Motif (SHM).The array geometry of GRSN was defined by seven stations and processed to associateseismic phase arrivals to define glacial events. Two stations of GRSN were assigned the roleof reference sites. The long-period surface wave characteristics of the event signals withmagnitudes M 4.9, M 4.8, M 4.7, and M 4.7 were detected using filtering, beamforming,and location-relocation steps; then, the results were updated using SHM. The event datawere filtered with a Butterworth band pass filter of 35s-70s with a common amplification.Using the array-beamforming technique, the beam traces were computed to calculate thebeam-slowness (the apparent velocity) and the beam-azimuth of incoming wavefronts forparticular time intervals to further analyze the observed glacial events. Then, the detectedevent signals were relocated and used to estimate array parameters; beam-slowness andbeam-azimuth. Finally, in this study, the array processing technique was used with arrayparameters computed from the SHM to detect and analyze the slow glacial events using thearray installation data from GRSN.