Station-Specific Traveltime Tables In a 3D earth

Station-SpecificTraveltime 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 informationCrust 2.0Pn tomographySurface 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 AK135differential 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