Source characteristics of the Sinaia (Romania) sequence of May–June 1993

A particular sequence of crustal earthquakes ( h < 10 km, M L < 5.1) occurred in the southwestern extremity of the Eastern Carpathian arc bend (Sinaia region) starting on May 4, 1993. The main shock ( M L 5.1) occurred on May 23 after significant 20-day foreshock activity. The first locations delineate an epicentral area of approximately 225 km 2, elongated in a NW-SE direction, which agrees with the fault plane solution for the main shock. The digital recordings of the Romanian telemetered network are analyzed in order to estimate source parameters and to investigate scaling relations. An empirical deconvolution technique and the spectral ratio method are used for this purpose. The main results, such as (1) the departure from a M 1 3 o scaling of the source radius as a function of the seismic moment, (2) the scaling of the peak velocity parameter as a function of local magnitude and (3) the scaling of the dynamic stress drop with earthquake size, are interpreted in terms of an inhomogeneous source model.