| Abstract Submission No. | ABS-3.1-0074 |
| Title of Abstract | W- Phase Centroid Moment Tensor Inversion of the 29 th July 2025 Kamchatka earthquake: Constraints from very-long period waves |
| Authors | Athul Palliath*, Himangshu Paul |
| Organisation | CSIR National Geophysical Research Institute |
| Address | ALANTHOD HOUSE , PO IRIVERI , MIDAVILODE KANNUR, Kerala, India Pincode: 670613 E-mail: athulgeophysics@gmail.com |
| Country | India |
| Presentation | Oral |
| Abstract | The W-phase provides a very-long-period (100¿1000 s) window for rapid, stable source characterization of great earthquakes. We analyze the 29 July 2025 Kamchatka megathrust event, where the Pacific Plate subducts obliquely beneath the Okhotsk Plate along the Kuril¿Kamchatka margin. We perform a manually supervised W-phase centroid moment tensor inversion of three-component teleseismic records from 12 long-period FDSN stations, filtered to 0.001¿0.005 Hz. Synthetics are generated from a Pyrocko Green¿s-function store using a spherical-Earth normal-mode approach with the ak135-f velocity model. Source-time functions are half-sinusoids with duration treated as a parameter searched from 50 to 600 s. The best-fitting W-phase solution indicates a great (Mw 8.82) oblique-reverse, near double couple source on the plate interface, with seismic moment M₀ ≈ 2.2 × 10²² N·m, a shallow centroid at 19 km depth, a 113 s centroid-time delay relative to origin time, and a total effective source-time duration of 155 s; the Mw is consistent with the USGS estimate. The centroid is at about 19 km depth and located approximately 244 km to the SSW (azimuth 211°) of the hypocenter broadly trench-parallel indicating a predominantly along-strike bias in moment release inferred from the W-phase CMT. Coherent very-long-period fits across the network with ensemble behavior showing tight well-constrained Mw and no required non-DC component. This study provides results with robust constraints for subsequent finite-fault and first-order tsunami modeling. |
| Keywords | cmt,w-phase,kamchatka,earthquake |