Station-Specific Traveltime Tables In a 3D earth.

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Presentation transcript:

Station-Specific Traveltime Tables In a 3D earth

Goal: improve earthquake locations while minimizing computation effort through precomputation

Three-D earth model elliptical earth model ½ degree resolution, tetrahedral splines based on available structural information Crust 2.0 Pn tomography Surface wave tomography

Overall organization into interfaces Small-scale organization into tetrahedra Linear interpolation within tetrahedra implying rays that are circular arcs

First Cut at building a 3-d MODEL Simplified, 2-layer-crust version of Crust 2.0 on top of AK135 mantle with sub-Moho velocities adjusted to match Crust 2.0 Pn velocities

Strategy Compute differential traveltimes between 3D model and reference vertically-stratified model one traveltime calculation for each station gives traveltime correction for earthquake anywhere in the US to that station

Examples Crust2 minus AK135 differential traveltimes

Shadow zone

Sensitivity Test Test grid of earthquake hypocenters Current US station configuration Traveltimes for 3D model Location using AK135 Assess location error

Stations east of California

Location Errors: = 0.5 degree Note: this preliminary calculation used data from a limited number of stations