Estimation of finite seismic source parameters for selected events of the West Bohemia year 2008 seismic swarm

Finite seismic source parameters were determined for a set of 91 selected events of the West Bohemia year 2008 earthquake swarm (ML from 0.6 to 3.7) using the stopping phases method. According to the theory, two stopping phases are generated along the source border where the rupture process terminates. These two phases form a Hilbert transform pair; it is also a criterion for their identification. Circular and elliptical source models were considered and their parameters were recovered using the differences in arrival times between the identified stopping phases. Generalization of the circular to elliptical model was found to be statistically significant only for a minority of the events; consequently, only circular source models were investigated in detail. Individual source parameter errors were estimated with the use of the jackknife method. Our results are in good agreement with a previously published theoretical formula relating source radius and magnitude and also with the relation derived in the year 2000 swarm. Our results also confirm rather well the general theoretical assumption about the constant stress drop (with median value of 2.4 MPa and with the majority of values ranging from 1 to 10 MPa).