Abstrakt
The self-similarity of earthquake rupture scaling is a subject of ongoing debates. The output of multiple recent studies agrees on the fact that stress drops of earthquakes varies from 0.1 to 100 MPa over a broad range of seismic moments.
We investigated the source parameters of 56 earthquakes in the magnitude range M-L from 0.8 to 3.3 occurred during the 2000 and 2008 swarm in West Bohemia/Vogtland in order to learn if the source scaling of these, most-likely fluid triggered events, differ from the observations in other seismogenic regions around the world. We used two approaches to calculate the corner frequency in the frequency domain: inverting for the corner frequency f(c) of the displacement spectra and integrating of spectra by the method of Snoke.
A single f(c) for all stations was determined with attenuation correction defined by inverting for an event-dependent Q-factor. Similar dependence of the corner frequency on seismic moment was observed in the form f(c) proportional to M-0(-0.2), which is a much weaker scaling than expected for a constant stress drop model.
Accordingly, the stress drops vary from 1 to 130 MPa and appears to grow with seismic moment as delta Sigma proportional to M-0(0.43). The non-self similarity of the swarm earthquakes is supported by rather wide span of apparent stress ranging between 0.3 kPa and 1.2 MPa.