Qinv

This package is for seismic attenuation characteristics (Q value) analysis based on borehole observations.

• Author: Sheng Wang
• Email: wangsheng.cas(at)gmail.com

Table of content

• Library Dependence
• How to Install
• Tools
• Examples
• Citation

1. Library Dependence

fftw3 is required for this package.

2. How to Install

make
make install

Then, add the generated directory of your path to Qinv/bin/ into your PATH.

3. Tools

Binary

• polarizeP: invert the Back-Azimuth given NEZ components, and generate corresponding radial and the tangential components;
• findBestWin: find the optimal time window, and lag time for incident and the surface reflected waves;
• qinv: invert frequency-dependent Q values given single tangential seismogram, and the time windows for incident and reflected waves;
• stackQ: stack inverted Q values by sets of seismograms at a single station to get stable values.

Script for volume production

• findBestWinSet.py: batch processing for findBestWin.
• qinvSet.py: batch processing for qinv.
• stackQ.py: batch processing for stackQ.

Binary tests

All binaries with name format of test_... are for dev unit tests.

• test_atten:
• test_crossSpec:
• test_findBestWin:
• test_polarize:
• test_qinv:
• test_qjob:
• test_ranStack:
• test_stackQ:
• test_tracef1d:
• test_tracef1d_Spec:
• test_winopt:

4. Examples

Examples are in the directory of exam/, each of which as a script example, run.sh, for running.

4.1 exam_polarize_syn/

Polarization example using synthetic seismograms for inverting the Back-Azimuth given NEZ components, and generateingcorresponding radial and the tangential components.

Fig 4.1 Comparison of the radial and tangential synthetic seismograms (black lines), and the inverted seismograms(red lines) from polarizeP.

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4.2 exam_findBestWin_syn/

Determine the optimal time windows of incident and surface reflected waves.

Fig .2 Grid search isogram for the optimal windows of the incident and the surface reflected phases for synthetic tangential component. Waveform comparison is presented in Fig 4.3.

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4.3 exam_qinv_syn/

Invert frequency-dependent Q values from the incident and the surface reflected waves.

Fig 4.3 (up-left):The comparison of incident and the surface reflected phases. (up-right):The power spectrum comparison, black dash line presents the level of 70% maximum power. (low-left): The phase of the transfer function. (low-right): The inverted Q value. Please note that Q value is valid for the frequency band of (0.2, 0.6)Hz , in which the signal power is strong, and the phase of the transfer function is stable and approximates 0 degree.

5. Citation

Wang, S. and Li, Z., 2018. S-wave attenuation of the shallow sediments in the North China basin based on borehole seismograms of local earthquakes. Geophysical Journal International, 214(2), pp.1391-1400, https://doi.org/10.1093/gji/ggy223