Tez özetleri Astronomi ve Uzay Bilimleri Anabilim Dalı

Foreshocks and Their Characteristics, Examples from Turkey

In this study, foreshock activities of Dinar earthquake (1 October 1995, ML=6.0) and Buldan erathquake (26 July 2003, ML=5.6) were examined. Background activities for different time period were investigated for study areas by using the earthquake catalog which was provided by Kandilli Observatory and Earthquake Research Institute (KOERI). Calculations for this study were limited between coordinates of 37º-39ºN and 29º-31ºE for Dinar, and between coordinates of 37º-39ºN and 28º-30ºE for Buldan. By making use of the earthquakes which occur before and after the mainshocks, the investigation area was described as polygons. In these polygons, the seismicity parameters of 1900-2007, 1990-2007, 1995 (Dinar), 2003 (Buldan), and foreshock and aftershock activities were compared and the differences were presented. In this study, a and b values in Frequency-Magnitude Relationship were calculated by using the least squares and maximum likelihood methods. Thus p values were calculated for foreshock and aftershock activities by using Modified Omori power law decay relation. In order to investigate deviation of b value from regional characteristic, sliding window method was applied. The deviation was analysed on both event and time windows by using different window lenghts and window shifts. By analysing epicentral distribution and occurence time comprehensively, spatial and time distributions were detected for foreshock activities. Besides, by having focal mechanism solutions of the biggest foreshocks in both two foreshocks activities, consistence of their mainshocks were analysed. Consequently, contrary of the b value which was obtained in the background and aftershock acitivities, b values are decreasing significantly during the foreshock. It is observed that foreshocks have occured 12 days before the mainshock for Dinar and 25 days before the mainshock for Buldan, increasing their cumulative number with time. These activities were interrupted by two seismic quiescence periods. Spatial distribution of foreshocks are smaller than the spatial distribution of aftershock. The focal mechanism solutions of two biggest foreshocks occured in Dinar and in Buldan are consistent and similar to that of their mainshocks.

CEYLAN Savaş
Danışman : Y.Doç.Dr.Naşide ÖZER

Anabilim Dalı : Jeofizik Mühendisliği

Mezuniyet Yılı : 2008

Tez Savunma Jürisi : Y.Doç.Dr.Naşide ÖZER

Prof.Dr.Demir KOLÇAK

Prof.Dr.Bedri ALPAR

Prof.Dr.Niyazi BAYDEMİR

Prof.Dr.Yıldız ALTINOK