CC-FJpy: A Python Package for seismic ambient noise cross-correlation (CC) and the frequency-Bessel transform (FJ) method

Copyright

Xiaofei Chen Research Group

Department of Earth and Space Sciences, SUSTech, China.

Related article https://doi.org/10.1785/0220210042

Installation

Python 3 is required.

Anaconda environment is required for installation by make install.

Make sure that the CUDA and Python in the same version for you install and run.

Before Installation: Download & Compile fftw Library

make fftw

Installation for GPU version (default)

make
make install

If the nvcc compiler or $cudahome cannot be found, ccfjwill be compiled by default in the CPU version

Installation for CPU version

make cpu
make install

Usage

import ccfj

Cross-correlation (CC)

CCFs=ccfj.CC(
    npts,nsta,nf,fftlen,
    Pairs,startend,data,
    overlaprate=0.0,
    nThreads=8,
    fstride=1,
    ifonebit=0,
    ifspecwhittenning=1)

• npts: The number of points for data of one station read in
• nsta: The number of stations
• nf: The number of points of the frequency domain CC output
• fftlen: The number of points for one CC
• Pairs: A numpy array for Station Pairs, the dtype should be np.int32

You can use function GetStationPairs to generate Pairs.

startend: A numpy array records the start point and end point for each station, the dtype should be np.int32. For example, if the npts length is for one day, and station A have all of A day's data. Then for station A the startend is [0,npts]

• data: The seismic records, the dtype should be np.float32

• overlaprate: The rate for overlap, do not >= 1

• nThreads: The number of Threads for reading data and CC

• fstride: The output frequency stride

• ifonebit: if perform onebit

• ifspecwhittening: if perform specwhittenning

• CCFs: The output is the noise cross-correlation functions (CCFs)

According to our experience, ifonebit and ifspecwhittening, pick one of them is ok.

The specific example, please read example_CC.ipynb.

frequency-Bessel transform method (F-J method)

For ambient noise

out = ccfj.fj_noise(uf,r,c,f,fstride=1,itype=1,func=0,num=20)

The F-J Method for CCFs

• uf: the CCFs in the frequency domain

• r: the list of station distances (unit: m)

• c: the list of phase velocities you want to calculate

• f: the list of frequencies. The number of points of f should be consistent with the columns of uf

• fstride: stride of frequency for output

• itype: 0 for trapezoidal integral; 1 for linear approximate

• func: 0 for Bessel function; 1 for Hankel function

• out: the output dispersion spectrum

• num: the number of threads for cpu version (defult 20) and the device number of gpu version (default 0)

For earthquakes

out = ccfj.fj_earthquake(u,r,c,f,fstride=1,itype=1,func=0,num =20)

• u: the records in time domain

• r: the list of station distances (unit: m)

• c: the list of phase velocities you want to calculate

• f: the list of frequencies. The number of points of f should be consistent with the columns of uf

• fstride: stride of frequency for output

• itype: 0 for trapezoidal integral; 1 for linear approximate

• func: 0 for Bessel function; 1 for Hankel function

• out: the output dispersion spectrum

• num: the number of threads for cpu version (defult 20) and the device number of gpu version (default 0)

Mutli-windows F-J method (MWFJ)

This is mainly for earthquake

out = ccfj.MWFJ(u,r,c,f,Fs,nwin,winl,winr,taper=0.9,fstride=1,itype=0,func=0, num=20)

• u: the records in time domain

• r: the list of station distances (unit: m)

• c: the list of phase velocities you want to calculate

• f: the list of frequencies. The number of points of f should be consistent with the columns of uf

• Fs: The sample frequency

• nwin: number of time windows

• winl: list of left side of time windows

• winr: list of right side of time windows

• fstride: stride of frequency for output

• itype: 0 for trapezoidal integral; 1 for linear approximate

• func: 0 for Bessel function; 1 for Hankel function

• out: the output dispersion spectrum

• num: the number of threads for cpu version (defult 20) and the device number of gpu version (default 0)

Uninstall

make clean
make uninstall

References

Wang, J., Wu, G., & Chen, X. (2019). Frequency‐Bessel Transform Method for Effective Imaging of Higher‐Mode Rayleigh Dispersion Curves From Ambient Seismic Noise Data. Journal of Geophysical Research: Solid Earth, 124(4), 3708-3723. doi:10.1029/2018jb016595

Wu, G.-x., Pan, L., Wang, J.-n., & Chen, X. (2020). Shear Velocity Inversion Using Multimodal Dispersion Curves From Ambient Seismic Noise Data of USArray Transportable Array. Journal of Geophysical Research: Solid Earth, 125(1), e2019JB018213. doi:10.1029/2019jb018213

Li, Z., & Chen, X., (2020). An Effective Method to Extract Overtones of Surface Wave from Array Seismic Records of Earthquake Events. Journal of Geophysical Research: Solid Earth, 125(3), e2019JB18511. doi:10.1029/2019jb018511

Li, Z., Zhou, J., Wu, G., Wang, J., Zhang, G., Dong, S., Pan, L., Yang, Z., Gao, L., Ma, Q., Ren, H., & Chen, X. (2021). CC-FJpy: A Python Package for seismic ambient noise cross-correlation and the frequency-Bessel transform method. Seismological Research Letters. doi:10.1785/0220210042