Seismicity Rate Changes along the Central California Coast due to Stress Changes from the 2003 M 6.5 San Simeon and 2004 M 6.0 Parkfield Earthquakes

The Dieterich (1994) Rate/State formulation was applied for the seismicity rate changes in the western part of the Hellenic arc to be investigated. The completeness magnitude of the shallow seismicity (h<60km) was firstly evaluated for different time windows. The spatio-temporal changes of these seismicity rates (reference rates) were studied then for the interevent periods between successive strong(M≥6.0) earthquakes. These changes were correlated with the Coulomb stress changes (ΔCFF) produced by the stronger events, through a Rate/State model which incorporates physical parameters associated with fault dynamics such as the tectonic stressing rate, fault constitutive parameters and frictional response of the rupture zones. The influence of the former parameters in the model performance wastested by evaluating the linear correlation coefficient between modeled and real earthquake production rates along with their confidence limits. Application of different parameter values was attempted for the sensitivity of the calculated seismicity rates and their fit to the real data to be tested. Given the geographical peculiarity of the Hellenic Subduction zone, that yields to high uncertainties in the earthquake focal parameter determination, the results demonstrate that the present formulation and the available data sets are sufficient enough to contribute to a robust seismic hazard assessment.

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SEISMICITY CHANGES DETECTION DURING THE SEISMIC SEQUENCES EVOLUTION AS EVIDENCE OF STRESS CHANGES

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11390 ◽

2017 ◽

Vol 43 (4) ◽

pp. 1994

Author(s):

A.C. Astiopoulos ◽

E. Papadimitriou ◽

V. Karakostas ◽

D. Gospodinov ◽

G. Drakatos

Keyword(s):

Temporal Distribution ◽

Aftershock Sequence ◽

Occurrence Rate ◽

Generation Process ◽

Seismicity Rate ◽

Seismic Sequences ◽

Epidemic Type Aftershock Sequence ◽

Stress Changes ◽

Lefkada Island ◽

Seismicity Rate Changes

The statistical properties of the aftershock occurrence are among the main issues in investigating the earthquake generation process. Seismicity rate changes during a seismic sequence, which are detected by the application of statistical models, are proved to be precursors of strong events occurring during the seismic excitation. Application of these models provides a tool in assessing the imminent seismic hazard, oftentimes by the estimation of the expected occurrence rate and comparison of the predicted rate with the observed one. The aim of this study is to examine the temporal distribution and especially the occurrence rate variations of aftershocks for two seismic sequences that took place, the first one near Skyros island in 2001 and the second one near Lefkada island in 2003, in order to detect and determine rate changes in connection with the evolution of the seismic activity. Analysis is performed through space–time stochastic models which are developed, based upon both aftershocks clustering studies and specific assumptions. The models applied are the Modified Omori Formula (MOF), the Epidemic Type Aftershock Sequence (ETAS) and the Restricted Epidemic Type Aftershock Sequence (RETAS). The modelling of seismicity rate changes, during the evolution of the particular seismic sequences, is then attempted in association with and as evidence of static stress changes

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SEISMICITY RATE CHANGES IN ASSOCIATION WITH TIME DEPENDENT STRESS TRANSFER IN THE REGION OF NORTHERN AEGEAN SEA, GREECE

Bulletin of the Geological Society of Greece ◽

10.12681/bgsg.11400 ◽

2017 ◽

Vol 43 (4) ◽

pp. 2093

Author(s):

K. M. Leptokaropoulos ◽

E. E. Papadimitriou ◽

B. Orlecka–Sikora ◽

V. G. Karakostas

Keyword(s):

Stress Field ◽

Stress Transfer ◽

Seismic Hazard Assessment ◽

Aegean Sea ◽

Occurrence Rate ◽

Coulomb Stress Changes ◽

Seismicity Rate ◽

Stress Changes ◽

Before And After ◽

Seismicity Rate Changes

The region of northern Aegean has suffered several strong earthquakes since the beginning of the 20th century, causing extensive damage and loss of lives. For the seismic hazard assessment in the area, several studies have been accomplished, among them being the ones dealing with the Coulomb stress changes due to the seismic slip caused by major earthquakes, in addition with the constant tectonic loading on the major regional faults. The aim of the present study is to evaluate if seismicity rate changes from 1964 to 2008 are associated with changes in the stress field. For this purpose the stronger events (Μw>5.8) that occurred in this period were considered and their contribution to the stress field evolution was investigated by calculations performed just before and after their occurrence. This influence was then examined in connection with the occurrence rate of small events (Μw > 3.8) for the respective time intervals. After defining the probability density function (PDF) of the small events distribution, a rate/state model was used to correlate static stress changes with seismicity rate and to compare the observed with the expected seismicity rate for each time period.

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