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UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-22 1:24 |
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Conference: Bucharest University Faculty of Physics 2024 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
Development and Application of a refined 1-D Velocity Model for Enhanced Earthquake Hypocenter Localization in the Tg. Jiu area
Authors:
Marius Mihai(1,2), Mircea Radulian(1,2,3,4), Andreea Craiu(1), Marius Craiu(1), Raluca Dinescu(1),Alexandru Marmureanu(1)
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Affiliation:
1) National Instiute for Earth Physics, Romania
2) University of Bucharest, Faculty of Physics
3) Romanian Academy
4) Academy of Romanian Scientists
E-mail
mnmarius81@yahoo.com
Keywords:
seimic area, velocity models
Abstract:
In seismology, the use of a one-dimensional (1-D) velocity model is standard practice for determining earthquake hypocenters. This study introduces a refined 1-D velocity model with station delays for the Tg. Jiu seismic region in Romania, developed using the VELEST code. This model is essential for accurate earthquake localization and provides a basic framework for future three-dimensional (3-D) seismic tomography studies. A dataset consisting of 1,039 P-wave and 888 S-wave travel times has been compiled from 46 seismic events that occurred during the seismic sequence that started in February 2023 in the Tg Jiu area. The seismic events were selected based on a high degree of location accuracy, with each event having at least 25 P-wave arrivals. These events were recorded by 38 seismic stations operated by the National Institute for Earth Physics (NIEP).
Three input velocity models, each with different layer thicknesses extending to a depth of 41 km, were evaluated to identify the optimal velocity structure. The results of the VELEST inversion led to minimal discrepancies between observed and computed first arrival times of P and S waves. Following 50 iterations, the root-mean-square (RMS) values of travel time residuals showed a significant reduction, nearing a minimum value. The vertical hypocenter distribution revealed that seismic activity in the Tg. Jiu region is predominantly confined to the upper 20 km of the crust, with a sparse distribution of events at greater depths.
The developed 1-D velocity model for Tg. Jiu exhibits slightly higher velocity values compared to standard global models, such as IASP91. Station delays for P and S-waves reflect lateral geological variations that correspond with surface geology. This comprehensive velocity model enhances the accuracy of earthquake hypocenter determinations and provides deeper insights into the seismic and geological characteristics of the Tg. Jiu area.
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