|Title||Detailed rupture imaging of the 25 April 2015 Nepal earthquake using teleseismic P waves|
|Publication Type||Journal Article|
|Year of Publication||2015|
|Authors||Fan W.Y, Shearer PM|
|Journal||Geophysical Research Letters|
|Type of Article||Article|
|Keywords||array; backprojection; earthquake; hybrid back-projection; radiation; sea; Seismology; sumatra-andaman earthquake|
We analyze the rupture process of the 25 April 2015 Nepal earthquake with globally recorded teleseismic P waves. The rupture propagated east-southeast from the hypocenter for about 160km with a duration of similar to 55s. Backprojection of both high-frequency (HF, 0.2 to 3Hz) and low-frequency (LF, 0.05 to 0.2Hz) P waves suggest a multistage rupture process. From the low-frequency images, we resolve an initial slow downdip (northward) rupture near the nucleation area for the first 20s (Stage 1), followed by two faster updip ruptures (20 to 40s for Stage 2 and 40 to 55s for Stage 3), which released most of the radiated energy northeast of Kathmandu. The centroid rupture power from LF backprojection agrees well with the Global Centroid Moment Tensor solution. The spatial resolution of the backprojection images is validated by applying similar analysis to nearby aftershocks. The overall rupture pattern agrees well with the aftershock distribution. A multiple-asperity model could explain the observed multistage rupture and aftershock distribution.
We observe a relatively compact rupture pattern that agrees well with the aftershock distribution. A multiple-asperity model can explain the observed multistage rupture and the aftershock distribution. The apparent rupture velocity is significantly higher than S wave speed during the Stage 2 rupture, but we cannot be sure that this represents the true rupture speed. Given the current plate convergence rate, the Mw 7.8 earthquake is smaller than expected [Ader et al., 2012]. Therefore, detailed imaging of the rupture process is important for future hazard assessments.