Static Earthquake Triggering Of Central Himalaya In Pakistan Region By Coulomb Failure

Abstract

The study area extends 1200 kilometers in Northern Pakistan, located in the Central Himalayas. This region includes major faulting of MBT, MCT, MKT, MMT and other faults. This region has been the site of numerous devastating earthquakes. So far, very few studies have been conducted to determine earthquake/fault interaction and hazard assessment of this region. The aim of this research is to understand the static earthquake stress triggering in Central Himalayas Pakistan region. For this, historical/instrumental earthquake catalogues were compiled to choose the major earthquakes, having magnitude ≥6.0. The final earthquake sequence comprised of twelve earthquakes, spanning from 1905 to 2005. By employing static earthquake triggering theory on the final earthquake sequence, we have calculated co-seismic stress changes caused by particular earthquake as well as the impact of earthquakes on the impending earthquakes by incorporating the visco-elastic relaxation. To verify the robustness of numerical results, various values for co-efficient of friction (0.2, 0.4 and 0.6) and various values of viscosities such as (1.0×1019 and 1.0×1020 Pa.s) were chosen for the lower crust and the upper mantle. Further, the areas that are in high CFS zones and have potential to trigger upcoming earthquakes were analyzed. Out of twelve earthquakes the one earthquake is caused by previous earthquake. That earthquake is the Aftershock of 2005 Kashmir earthquake having magnitude of 6.4Mw is occurred in high CFS lobe. This earthquake was triggered by the co-seismic CFS changes caused by the 2005 earthquake (Main shock). This is the only time-dependent earthquake in this sequence which has been triggered by a preceding earthquake. The remaining eleven earthquakes in the sequence are all independent. Results reveal that the role of earthquake triggering is ineffective in this study area. Therefore, it can be deduced that the cause of earthquakes