| |
 |
UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 17:58 |
 |
|
|
|
Conference: Bucharest University Faculty of Physics 2016 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
The Vp/Vs and Poisson rations of the Romanian upper crust as derived from local crustal earthquakes
Authors:
Stoicescu Daniel(1), Manea Liviu(2), Borleanu Felix(2)
Affiliation:
E-mail
daniel.stoicescu18@gmail.com
Keywords:
seismic waves propagation, modified Wadati diagram, seismic velocities and Poisson ratios, upper crust
Abstract:
Romania is one of the most seismically active regions of Europe, the largest intermediate depth earthquakes occurred at the Carpathians bending zone producing serious damages at large distances. Besides the intermediate depth seismicity occurred in a narrow epicentral and hypocentral region, a crustal seismicity characterized by moderate magnitudes was highlighted as well. During the last decade, the number of seismic stations installed in Romania increased significantly. This led to an improving of detection capability as well of the source parameters estimations for various regions. Thus, the knowledge about source parameters and travel times of different seismic waves were extended giving valuable information about the Earth structures. The Romanian seismotectonics complexity has already been emphasized by the seismic tomography or receiver function investigations focused on specific regions. The present study aims to determine the seismic velocities Vp / Vs and Poisson ratios for the Romanian upper crust and correlate them with the already known geophysical and tectonic features. To achieve this goal the modified Wadati diagram was used, taking into account only direct waves of seismic events with depths up to 30 km. The Poisson ratios were determined through a nonlinear approximation directly from the seismic velocities ratios. The results show an increasing tendency of velocities ratios for the areas where the sedimentary layer is more pronounced as well as in areas of Neogene volcanism while a decreasing trend was emphasized at the contact between the Moesian Platform and the Southern Carpathians as well as for parts of the west and north-western part of the country. The study highlights as well an insufficient station coverage for several regions.
Acknowledgement:
This work was partially supported by: the Nucleu Program supported by ANCSI, Project number PN 16 35 03 07. Several techniques applied in the present study were developed within the international project FA7022-11-C-001. Data used in the present study were provided by the National Institute for Earth Physics (Romania) and processed within the National Data Centre in Magurele. GMT by Wessel and Smith (1995) was used to plot several figures.
|
|
|
|