UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS

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Conference: Bucharest University Faculty of Physics 2009 Meeting


Section: Atmosphere and Earth Science; Environment Protection


Title:
Statistical investigation of the time-space-size fluctuations in the Vrancea intermediate-depth earthquake catalog


Authors:
M. Rogozea, M. Popa, M. Radulian


Affiliation:
National Institute for Earth Physics, P.O. Box MG-2, 077125, Bucharest-Magurele, Romania


E-mail
mrogozea@infp.ro


Keywords:
Vrancea, earthquake, magnitude of completeness


Abstract:
Variations in the seismic activity are essential in understanding the evolution of the seismogenic system. However, various studies showed that such variations can be ascribed not only to natural, but to artificial causes as well. Among the main artificial causes could be: introduction of a new software for earthquake monitoring and processing, removal or introduction of seismograph stations, changes in magnitude definition, differences in station averaging techniques of amplitude data, differences in station corrections, adding data from temporary networks etc. In the present paper we apply various tools developed for the analysis of the earthquake catalogs as well as for detailed studies of seismicity characteristics in the case of Vrancea intermediate-depth earthquakes. The ROMPLUS catalog (Oncescu et al., 1999- updated) for events occurred between 1995 and 2008 is considered. In most of cases, the event location and magnitude are evaluated using waveform (digital) data. Multiple statistical tests are performed in order to investigate time and space variations of the magnitude of completeness (Mc), seismicity rate, frequency-magnitude distribution. The magnitude of completeness reflects the capability of the network to determine the location and size of an event with acceptable accuracy in different segments of the seismogenic region. Our statistical analysis identifies the specific variations for different time intervals, space segments and magnitude ranges in the considered time interval. The possible artificial biases are removed before interpreting the periods of increased/decreased seismicity as well as of the magnitude range affected by these changes.