| |
 |
UNIVERSITY OF BUCHAREST
FACULTY OF PHYSICS Guest
2024-11-23 18:26 |
 |
|
|
|
Conference: Bucharest University Faculty of Physics 2009 Meeting
Section: Atmosphere and Earth Science; Environment Protection
Title:
The statistical tidal tomography - a new investigation method for the intermediate-depth seismic activity
Authors:
Nicoleta Cadicheanu
Affiliation:
Institute of Geodynamics of the Romanian Academy, Bucharest
E-mail
nicoleta_cadichian@yahoo.com
Keywords:
earth-tides, earthquakes, HiCum, Schuster`s test. permutation test, statistical tidal tomography
Abstract:
The possibility that Earth-tides could be triggering seismic events has been investigated by many authors. Tidal influences of the semi-diurnal waves on the intermediate seismic activity were found. One of the triggering reasons of the earthquakes could be the gravitational modulations induced by earth tides, realizing a temporal coupling with the seismic activity. At the depth of intermediate and deep earthquakes, the Earth tides are the main outside force with very deep modulation depending of the solar and lunar orbital parameters which could affect with periodicity as shorter as 24 hours (diurnal band) or 12 hours (semi-diurnal band) the dynamic of the Earth.The parameter p used to validate this coupling was defined by means of two statistical tests with relatively different mathematical algorithms, Schuster’s test and permutation test, assuming null hypothesis for random distribution. In addition, it has been noted certain long-term periodicity of the time windows, to call synchronization intervals, in which these influences are present. These tests have been applied on the seismic event distributions obtained with the aid of HiCum method in sliding windows. We have extended this methodology to the different layers in the case of intermediate-depth seismic zones, using the relative new concept of "statistical tidal tomography".A systematic temporal pattern of the p-values preceding and following the occurrence of strong earthquakes was also observed for the Vrancea seismic zone. A "statistical tidal tomography" map for this intermediate-depth seismic zone is obtained when stacking function is shifted in 3D geometry following the epicenter distribution. Possibly, tidal tomography patterns of the intermediate-depth seismic activity represent reaction of regional tectonic structure to the earth-tides. Following the 3-D distribution of p<5% values in different sliding time windows, a periodical upward migration of the certain volumes in which seismic activity synchronize with semi-diurnal tide component, was observed.
|
|
|
|