Statistical Models of the Seismicity of the Vrancea Region, Romania

A parameterization derived from the Weibull distribution is used to model the seismic activity of the Vrancea region. The analysis of 498 crustal earthquakes with local magnitudes greater than 2.0, and 1377 subcrustal events with local magnitudes greater than 2.5 emphasizes that the shallow sequences show a strong clustering tendency, while the intermediate depth mainshock sequences are modeled by a completely random pattern in space and time. These results are not influenced by the magnitude threshold and the width of the time window. The difference between the seismicity patterns in the crust and in the subcrustal zone correlates with the difference between the stress field within these two regions. Copyright Kluwer Academic Publishers 1999