Hypocenter relocation and velocity model for major earthquakes in northwest Himalaya
- PDF / 10,551,127 Bytes
- 13 Pages / 595.276 x 790.866 pts Page_size
- 5 Downloads / 183 Views
ORIGINAL PAPER
Hypocenter relocation and velocity model for major earthquakes in northwest Himalaya Perveiz Khalid 1
&
Shahzada Khurram 1 & Zahid Raza 1
Received: 8 July 2019 / Accepted: 27 October 2020 # Saudi Society for Geosciences 2020
Abstract The proper understanding of earthquake geometry and location is very important to understand the seismicity of an area. In the present study, 185 earthquakes that occurred in the northwest Himalaya of magnitude Mw > 0.6 between 2010 and 2013 were relocated using the Modified Joint Hypocenter Determination method. After examining seven velocity models, average VP/VS ~ 1.73 computed by Wadati diagram is used to improve the hypocenter locations of the earthquakes. Based on hypocentral distributions, these earthquakes were classified into four groups. Group 1 is along the Punjal Thrust in Hazara Kashmir Syntaxes. Group 2 belongs to the Indus-Kohistan Seismic Zone whereas group 3 is along the Besham dome and the fourth group is along the Main Mantle Thrust. Shallow crustal earthquakes were relocated to 0–50 km, deep earthquakes were relocated to 50–100 km, and much deep earthquakes were relocated to 250–350 km depth. This analysis will be helpful to understand the seismicity of the northwest Himalaya of Pakistan. Keywords Hypocenter relocation . Modified Joint Hypocenter Determination . IKSZ
Introduction Pakistan is situated in a very active tectonic zone, which includes ongoing collision between the Indian and Eurasian Plates, the junction of the world’s largest mountain ranges— the Himalayan, the Hindu Kush, and the Karakorum. Tectonically, Pakistan is composed of diverse geological/ tectonic features because of its location. The major cause of seismicity in the northwest Himalaya and northern side of Pakistan is related to the continuous northward subduction of the Indian plate beneath the Eurasian plate. The Indian plate moves at a rate of 3.7 cm/year relative to the Eurasian plate (Gordon et al. 1999). As a result of this continuous Responsible Editor: Amjad Kallel * Perveiz Khalid [email protected] Shahzada Khurram [email protected] Zahid Raza [email protected] 1
Institute of Geology, University of the Punjab, Lahore 54590, Pakistan
subduction, the world’s highest mountain ranges—the Himalayas, Karakorum, Pamir, and Hindu Kush—have been formed. Major thrust faults such as Main Karakorum Thrust (MKT) and Main Mantle Thrust (MMT), Main Boundary Thrust (MBT), Indus-Kohistan Seismic Zone (IKSZ), and other active faults of variable lengths have been produced due to the north and north-east directed compression as shown in Fig. 1. A wedge-shaped NW-trending IKSZ was first delineated by Armbruster et al. (1978) using microseismic data for the period 1973–1974. Later on, different researchers confirmed the presence of this 100-km-long and 50-km-wide IKSZ between HKS and MMT (Seeber and Armbruster 1979; Ni et al. 1991). Seeber and Armbruster (1983) developed a seismotectonic model for Hazara Kashmir Syntaxis (HKS) region by using microseismic data of Tarbela
Data Loading...
