Seismological monitoring of magmatic and tectonic earthquakes in the East Eifel Volcanic Field, Germany

Abstract

In 2013 there were reports on exceptionally deep earthquakes in ca. 40 km depth below the intraplate East Eifel Volcanic Field, Germany. Due to this observation the regional seismological monitoring network was improved to better explore this unusual seismicity. In order to acquire the necessary instruments, financial resources, and man power, a close partnership was initiated between the local state seismological service and academic research institutions. As an outcome the seismological field experiment called Deep Eifel Earthquake Project – Tiefe Eifel Erdbeben (DEEP-TEE) was accomplished which measures high-quality ground motion recordings since 2014. These measurements are used to study deep magmatic processes around the Laacher See Volcano (LSV) which was the site of a paroxysmal eruption just 13,079 years ago. As the DEEP-TEE network is located in a region with a high cultural noise and loose sediments, a careful site selection was a major task. Here, the network design is described and its recordings are used to determine 1-D seismic velocity models (vp, vs, and vp / vs) with station delay times to relocate the seismic events. The models include a priori information from active seismic experiments, especially in the mantle, to overcome resolution problems. The new velocity models allow to (re)locate the local earthquakes with horizontal and vertical uncertainties of ca. 0.5 km and 2.0 km, respectively. A special highlight of DEEP-TEE is the frequent observation of deep low-frequency (< 10 Hz) earthquakes whose hypocentres outline an active translithospheric channel, feeding the magmatic-fluid-volatile system underneath the LSV.