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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-24 9:30 |
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Conference: Bucharest University Faculty of Physics 2011 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
A new magnitude relation for intermediate-depth Vrancea earthquakes
Authors:
Craiu Marius
Affiliation:
National Institute for Earth Physics, Magurele
E-mail
gcraiu@infp.ro
Keywords:
magnitude, amplitude Wood Anderson
Abstract:
The seismic activity on the Romanian territory consists of both shallow and intermediate-depth earthquakes. The subcrustal activity is concentrated at the bend of the Carpathian arc (Vrancea region) within a confined focal volume in the depth range from 60 to180 km. The subcrustal earthquakes generated here are of the largest magnitude throughout the Carpathians (Mw=7.9 maximum recorded magnitude). The crustal seismicity is moderate and more scattered in comparison with the intermediate-depth one.
In this paper we approached the problem of the homogeneous determination of local magnitude for Vrancea depth-intermediate earthquakes.As a first step , we build a database of real Wood Anderson amplitudes deduced from the available data, maximum peak-to peak amplitudes are measured on the horizontal components of a broad-band sensor.
The data base includes a set of 467 intermediate-depth earthquakes with magnitudes MD= 2.3-5.7 and depths between 60-150km, recorded in 2007-2009 time period. The amplitude (A) was measured on the horizontal components of broadband seismograms filtered to reproduce synthetic Wood-Anderson seismograms (in millimeters.The duration magnitude (MD) are used as reference to estimate a new magnitude scale from amplitudes. We determined for Vrancea zone the new coefficients (c0-c4) through the multiple regression method.
The resulting set of the new magnitudes proved to be definitely better constrained than the one obtained by present day procedures at the National Institute for Earth Physics.
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