NonLinLoc

Probabilistic, Non-Linear, Global-Search Earthquake Location in 3D Media. Operates on UNIX based systems (Linux, Solaris, Mac OS X, ...)

The NonLinLoc (Non-Linear Location) package is a set of programs for velocity model construction, travel-time calculation and probabilistic, non-linear, global-search earthquake location in 3D structures, and for visualisation of 3D volume data and location results. Many of the programs operate with a 3D Grid structure which defines a specific, gridded, rectangular volume (Non-GLOBAL mode) or spherical section (GLOBAL mode).

See the NLLoc program documentation for a description of the non-linear location inversion approach and algorithms.

NonLinLoc supports regional/teleseismic location in a spherical, longitude/latitude/depth coordinate system. This is referred to as the "GLOBAL" mode in this documentation. The original rectangular-Cartesian location mode remains fully supported, and is referred to as the "Non-GLOBAL" mode where relevant.

NonLinLoc includes the Equal-Differential Time (EDT) likelihood function in addition to the classic L2/RMS function (see EDT likelihood function).

NOTE: Currently, the NonLinLoc package only includes software support for generating 1D, spherically-layered travel time grids for GLOBAL mode location. External software can be used to generate 3D travel time grids in spherical coordinates for GLOBAL mode. (A Fast Marching Method, finite-differences package for calculating travel times on 3D spherical-ellipsoidal grids is currently under development, contact Anthony Lomax for more information anthony@alomax.net)