Abstract
Earthquakes are continuously monitored by a global network of several thousand seismic stations equipped with highly sensitive digital seismometers. The Geological Survey of Denmark and Greenland (GEUS) takes part in it by operating five seismic stations in Denmark and 18 in Greenland, some of the latter in collaboration with international partners. There are two main ways of detecting earthquakes from digital recordings of seismometers: (1) by a manual review of the data by an expert in processing seismic earthquake signals and (2) by an automatic method that uses a computerised algorithm to analyse the recordings.
Highlights
Earthquakes are continuously monitored by a global network of several thousand seismic stations equipped with highly sensitive digital seismometers
There are several reasons why an automatic detection procedure has not yet been implemented at GEUS: (1) historically, the staff at GEUS have conducted high-quality manual detection of earthquakes, based on a long tradition of manual seismogram analysis (Lehmann 1954), (2) the ambient noise level in Denmark is generally too high for small local earthquakes to be detected automatically and (3) in Greenland, the distance between the seismometers is too long for automatic methods
Previous tests on GEUS data showed that automatic detection using the so-called standard method resulted in a very high number of false detections, and the effort needed to distinguish real earthquake signals from noise signals was much greater than that needed in the manual method
Summary
Earthquakes are continuously monitored by a global network of several thousand seismic stations equipped with highly sensitive digital seismometers. Station Nord is located in eastern North Greenland, in a region where a major tectonic factor is the spreading that occurs along the rift zones in the northern North Atlantic and the Arctic Ocean (Døssing et al 2010), and which gives rise to high seismic activity (Fig. 1). Another tectonic factor is postglacial isostatic rebound that was the source of three major earthquakes in 1971, 1987 and 1993 (Chung 2002), with magnitudes of 5.1, 5.5 and 5.4 on the Richter scale. The basis of this method is two running time windows that both compute the average amplitude of the signal, one with a short
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