station-specific traveltime tables in a 3d earth
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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