Time-scale phase-weighted stack

Software to compute the time-scale phase-weighted stack (ts-PWS), including the two-stage stack and the unbiased phase coherence strategies (Ventosa et al., GJI 2017).

The software packages of fast phase cross-correlation and ts-PWS stacking are basic building blocks in the design of efficient signal extraction methods from interstation correlations.

Main features

• Fast: The time-frequency expansion used in the ts-PWS is implemented using frames of wavelets (Morlet and Mexican hat wavelets are available). The most demanding operation is conventionally reading the data.
• Better filtering: The two-stage stacking and the unbiased phase coherence help to reduce signal attenuation and increase noise attenation.
• Simple setup: All parameters are automatically set, e.g., when w0, Q or number of cycles is changed the parameters describing the frame are adapted accordingly.
• Resampling techniques: The bootstrap and jackknife techniques can be applied to build a pull of stacked sequences for a subsequent error analysis.

Compilation

To compile execute "make" in the src directory. Use "make clean" to remove any previouly compiled code.

• The Seismic Analysis Code (SAC) is used to read and write sac files.
• The SACHOME enviorment variable should provide the path to directory where sac is installed. For example, in bash this can be defined as:
  export SACHOME=/opt/sac
  Change "/opt/sac" to your current sac directory if necessary.
• OpenMP is used to speed up computations. When OpenMP is not available, use make -f makefile_NoOpenMP".

Warming up

1. Read ./examples/example.sh
2. Execute it, e.g., bash example.sh
3. Do ts-pws for the parameters usage.

Paper to be cited

Ventosa S., Schimmel M. & E. Stutzmann, 2017. Extracting surface waves, hum and normal modes: Time-scale phase-weighted stack and beyond, Geophysical Journal International, 211(1), 30-44, doi: 10.1093/gji/ggx284

Origin of PWS

Schimmel M. & J. Gallart, 2007. Frequency-dependent phase coherence for noise suppression in seismic array data, Journal of Geophysical Research, 112, B04303, doi: 10.1029/2006JB004680

Schimmel M. & H. Paulssen, 1997. Noise reduction and detection of weak, coherent signals through phase weighted stacks, Geophysical Journal International, 130, 497-505, doi: 10.1111/j.1365-246X.1997.tb05664.x

2020/10/01 Sergi Ventosa Rahuet (sergiventosa(at)hotmail.com)