资源环境科技发展态势分析平台

Coseismic surface deformation imaged through interferometric synthetic aperture radar (InSAR) measurements was used to estimate the fault geometry and slip distribution of the 2017 Mw 6.5 Ormoc earthquake along a creeping segment of the Philippine Fault on Leyte Island. Our best fitting faulting model suggests that the coseismic rupture occurred on a fault plane with high dip angle of 78.5 degrees and strike angle of 325.8 degrees, and the estimated maximum fault slip of 2.3 m is located at 6.5 km east-northeast of the town of Kananga. The recognized insignificant slip in the Tongonan geothermal field zone implies that the plastic behavior caused by high geothermal gradient underneath the Tongonan geothermal field could prevent the coseismic failure in heated rock mass in this zone. The predicted Coulomb failure stress change shows that a significant positive Coulomb failure stress change occurred along the SE segment of central Philippine Fault with insignificant coseismic slip and infrequent aftershocks, which suggests an increasing risk for future seismic hazard.

Plain Language Summary A shallow earthquake with magnitude 6.5 hit northern sector of Leyte Island along the Philippine Fault near the Tongonan geothermal field. This earthquake resulted in at least 4 fatalities and 100 injuries. The seismicity is not frequent, and no large earthquake has been reported on Leyte Island since the 17th century. As a result, this earthquake will increase the risk of seismic hazard on the surrounding fault system. Thus, the detailed investigation on the activity of the fault on Leyte Island is a crucial issue for earth scientist and governmental agency.