New Velocity Model of the Novy Kostel Intraplate Earthquake-Swarm Region, West Bohemia

Session: Alpine-Himalayan Alpide Shallow Earthquakes and the Current and the Future Hazard Assessments [Poster]
Type: Poster
Date: 4/30/2020
Time: 08:00 AM
Room: Ballroom
Description: 

The West-Bohemia region at the Czech-German border is well known for the occurrence of relatively frequent intraplate earthquake swarms and other manifestations of geodynamic activity, such as mineral and thermal springs, mofettes and Quaternary volcanism. Most of the earthquake activity during last three decades is concentrated in the vicinity of Novy Kostel. We processed data from selected microearthquakes of the seismic swarm which took place in the Novy Kostel region in 2008. Because of a high degree of lateral inhomogeneity assumed in the area, we focused on a relatively small vicinity of the Novy Kostel village. The radius of the circular region considered to determine the velocity structure underneath reaches 11 km. In this region we used very precise, manually checked, onset readings for both P and S waves from 137 selected events at 11 selected stations of the WEBNET network. An important selection criterion was the homogeneity of the data set meaning that the precise readings from all the selected events are available at all the selected stations. These data were used in the joint hypocenter-velocity inversion in which the so called isometric method was employed. The result is a new 1D velocity model of the upper crust down to the depth of 11 km and absolute locations of the selected earthquakes. Their foci delineate a steeply dipping fault plane strike of which is about 170 degrees from the north. We analyzed time residuals at individual stations and observed an azimutal dependence caused by anisotropy. No systematic dependence on epicentral distance was found within the target region, which means that the new 1D model seems to be a reasonable approximation of the real structure in the close vicinity of Novy Kostel. We averaged time residuals over the events and obtained the mean travel-time residuals at individual WEBNET stations. These values can be used to correct P or S travel times when using the new model to localize other events in the given region.

Presenting Author: Jiri Malek

Authors