Data Services Newsletter

Volume 16 : No 2 : Summer 2014

New Automated Surface-Wave Phase-Velocity Measuring System (ASWMS)

The Automated Surface-Wave Phase-Velocity Measuring System (ASWMS), developed by Ge Jin & James Gaherty (2014), was recently added to the IRIS DMC’s pool of data products. The ASWMS allows users to generate research-grade tomography maps with minimal user input or experience. Surface-wave phase-velocity measurement is an important observation to constrain the Earth’s shallow structure. Phase velocities are frequency dependent because surface waves of different wavelengths are sensitive to Earth structure at different depth. Traditional methods to estimate surface-wave phase velocity usually require manual manipulation of data, which can be challenging when processing large data sets. The MATLAB® based ASWMS package automatically downloads, analyzes, and measures the phase and amplitude of surface waves and then generates surface-wave tomography maps. Local data on disk can also be used. This cross-correlation based method can be applied to continental, regional or local scales as long as the array is dense enough such that inter-station distances are less than a few wavelengths of the shortest periods analyzed. The ASWMS package can provide near real-time surface-wave tomography maps with minimal user effort or computing resources. PASSCAL experiment PIs might find this an attractive way to quickly and easily investigate their own data as it’s being collected.

Examples of applying ASWMS to USArray and several PASSCAL experiments along with the short setup_parameters.m file used (“example“http://ds.iris.edu/media/product/aswms/files/EXAMPLEsetup_parameters.txt) are given on the product detail page.

http://ds.iris.edu/ds/products/aswms

This product was supported and partially funded by the IRIS DMC.

Jin, G., and J. B. Gaherty (2014), Surface Wave Measurement Based on Cross-correlation, Geophys. J. Int, submitted.

by Alex Hutko (IRIS Data Management Center) , Chad Trabant (IRIS Data Management Center) , Ge Jin (Lamont-Doherty Earth Observatory, Columbia University) and James Gaherty (Lamont-Doherty Earth Observatory, Columbia University)