سال انتشار: ۱۳۸۴

محل انتشار: دوازدهمین کنفرانس ژئوفیزیک

تعداد صفحات: ۹

نویسنده(ها):

نادیا طاهرنیا – دانشگاه آزاد اسلامی واحد تهران شمال
محمدرضا قیطانچی – دانشگاه تهران، موسسه ژئوفیزیک

چکیده:

To Study the seismicity of Pakistan and investigate the characteristics of the ٨th October ٢٠٠٥ destructive earthquake in north Pakistan, the source parameters of the recorded earthquakes by the seismic stations in the world during the past ٤٠ years as well as the recent earthquake in Pakistan and it’s aftershocks where collected. Then the epicenter distribution of earthquakes where over lapped on the faults map in the Middle East. Fault plane solutions of ٩٨ strong earthquakes in Pakistan and neighbouring regions in Afghanistan and India were determined by the polarity of initial p waves. In next stage, the seismic energy released by strong earthquakes in the region was determined from magnitude using Richter relation of magnitude – energy in each ٠,٥×٠,٥ sub square and plotted on the faults map of the region The fault offset of the main earthquake was calculated to be ٨ m, it’s source duration was about ٤٠ s and it cuased a faulting about ١٢٠ Km. it’s stress drop was calculated about ٤٠ bar. The fault offset of the strongest aftershock was calculated to be ٢,٥ m, it’s source duration was about ٣ s and it cuased a faulting about ١٠ Km. It’s stress drop was calculated about ١٤ bar. The result indicated that the Pamir- Hindu Kush region was seismically active during the past ٤٠ years which released significant seismic energy each year. Instrumental and historical data indicated that the hypocenter region of the recent earthquake in Pakistan did not show significant seismic activity during the past ١٠٠ years and describe a kind of seismic gap. In other words the recent earthquake is the largest one ever accured during the past ١٠٠ years. The recent earthquake is very similar to the ١٩٧٨ Tabas earthquake in Iran. The source mechanism of both earthquakes had trust type mechanisms and both had shallow depths and had very similar stress drop. Both earthquakes fallow many strong trust type aftershocks.