| Description: | [CCES Webinar] Dr. Hari Ram Thapa (International Center for Theoretical Physics (ICTP), Trieste, Italy) -- Crustal structure and discontinuities beneath the Nepal Himalaya using seismic ambient noise and teleseismic P-wave coda autocorrelation -::~::- Join: https://meet.google.com/nfg-occr-oqp -::~::- |
| Date: | Wednesday, Sep 06, 2023 |
| Time: | 3 p.m. - 4 p.m. |
| Details: | We present a new 3-D S-wave velocity structure of the crust beneath the Nepal Himalaya using ambient noise tomography (ANT). Our findings suggest that the lateral variation of S-wave velocity likely controls the rupture propagation and arrest of 2015 Gorkha earthquake. We further constrain crustal discontinuities beneath Nepal including the Main Himalayan Thrust (MHT) using teleseismic P-wave coda autocorrelation. The MHT geometry correlates well with sizable low S-wave velocity zones obtained from the ANT and separated by two ramps. The southernmost first ramp is where the 2015 Gorkha earthquake nucleated that we map up to the source model of the 1934 historical earthquake in Eastern Nepal. The northernmost second ramp is adjacent to the mid-crustal low velocity zone beneath south Tibet. In between the two ramps, we interpret the horizontal low velocity zone as the interseismic creeping patch of the MHT with down-dip extent of 50-70 km length and 90-100 km in correspondence with the Mw 7.8 2015 and 8.4 1934 source models, respectively. A systematic mapping of the low-velocity zones in relation to the MHT integrated with GPS geodesy along with the respective slip from individual past earthquake ruptures can help decipher the paradox of maximum Himalayan earthquake magnitudes. |
| URL: | https://meet.google.com/nfg-occr-oqp |
| Calendar: | Seminar Calendar (entered by sanjaykm) |