The Romanian earthquake of August 30, 1986: A study based on GEOSCOPE very long-period and broadband data

Abstract

The Romanian earthquake of August 30, 1986 is the second largest intermediate depth event in this area since the worldwide deployment of digital instrumentation, and the first one since the installation of GEOSCOPE network. It offers the unique opportunity to document this well-known but poorly understood zone of deep continental seismicity using high quality teleseismic data in different frequency bands. The source is well constrained both from very-long period surface wave data observed on GEOSCOPE stations and, independently, from body wave modelling at various worldwide stations. The depth obtained is approximately 140 kilometers, the seismic moment, 0.8 1027 dyne-cm and the mechanism from both data sets is very similar to that of the previous 1940 and 1977 Vancrea events, indicating that these events, although having occurred at noticeably different depths, are expressions of the same tectonic process. However, from the detailed study of the source using broadband data, it can be inferred that the source presents much less complexity than the 1977 event.