SATELLITE TECHNIQUES CAN UNEARTH DEEP-SEATED EARTHQUAKE GENERATION TECTONICS: A CASE STUDY OF SATELLITE GRAVITY MODEL FOR OCTOBER 28 & 29, 2008-EARTHQUES OF BALOCHISTAN, PAKISTAN
- Paper number
IAC-09.A2.I.1
- Author
Prof. Nayyer Alam Zaigham, HEC, Pakistan
- Coauthor
Mr. Zeeshan Alam Nayyar, University of Karachi, Pakistan
- Year
2009
- Abstract
Pakistan is situated on the western-rifted margin of the Indo-Pakistan subcontinental plate. Tectonics of the country is dominantly the result of various phases of collision, convergence and rift events. Central north-south oriented Fold-Thrust Belt of Pakistan shows fabulous structural bending and syntaxural trends enveloping parallel mountain ranges and structural valleys. On 28-October-2008, a damaging relatively high magnitude earthquake of 6.4Mw occurred at 23:09:57.65 UTC, lat. 30.64N & long. 67.35E, depth: 15 km, in E-W bending Khanozai-Muslimbagh structural valley for the first time. After about 12-hours, another similarly high magnitude earthquake of 6.4Mw occurred on 29-October-2008 at 11:32:43.13 UTC, lat.:30.60, Long.:67.46, depth: 14km, in NW-SE striking narrow thrust-faulted valley of Ziarat about 45km southeast of Khanozai locality. In the Ziarat area, geologically young sedimentary rocks have been intensely thrusted, folded and squeezed by tectonic forces whereas no such intense geological setup is mapped in the Khanozai valley. Significant life & property damages have been reported due to landslides and collapses of poor-structural houses. About 74 aftershocks of moderate magnitudes quakes have also been recorded within three days in the NW-SE striking zone parallel to Ziarat valley, but the zone strikes across the Khanozai valley indicating complexity of seismicity distribution. Present study shows an exotic relationship of seismicity trend with the exposed tectonic structural trends as revealed from the satellite image terrain and the geological maps. On the other hand, the satellite gravity-gradient map, deduced from the satellite gravity map of the earthquakes’ affected study area, reveals an excellent tectonic deep-seated basement structural trend, which corresponds with the exotic trend of the current seismicity zone striking across the Khanozai-Ziarat region of complex geological setup. However, it is also inferred base on the analysis of centroid moment tensor at lat.30.990 & long.67.395 that the shocks were caused by either left-lateral slip on a northeast-striking fault or right-lateral slip on a northwest-striking fault beneath the fold-and-thrust belt at depth of about 10-15 km as revealed from satellite gravity analysis. Present paper describes the details of research study carried out to develop the seismo-tectonic model in the tectonically complex region of Balochistan Province, Pakistan.
- Abstract document
- Manuscript document
(absent)