Introduction

STK is a tool for seismic data processing; main features are:

• Data format: SAC ASCII and SAC_BIN are the format supported; until 200 files (tested with 120) can be read in a directory.

• Filtering the data: all filters are causal recursive IFR (Infinite Impulse Response) written using the bilinear Z-transform in the time domain. Their conception using a few number of coefficents gives them very fast with a low memory cost. The adaptation factor of frequency warants no deformation in the frequency domain of the transfert function. The main filters used are the following: Butterworth High-Pass and Low-Pass (n order), Farrer 10s-6s Low-Pass (a combination of rejector and Low-Pass specially designed for removing oceanic noise), Integrator, Derivator, Integrator with cut-off frequency, Derivator with cut-off frequency, Trend removing, Rejector (n-order), Envelop with Hilbert (not recursive at all), compensator of (n-order), Polynomial filter (n-order, not recursive at all ).

• Data plotting: channel by channel, all channels, zoom, unzoom, unfilter, instantaneous time and amplitude informations with mouse pointer

• Fourier domain: Power Spectral Density (PSD) in linear-linear, log-log axes; independant windows for each channel, instantaneous frequency and amplitude informations with mouse pointer, zoom, unzoom of spectra. Dirac, Hilbert transform, Time-Frequency representation (tested until 1 million of points per channel on 3 channels.

• Polarization: easy and fast particule motion representation in both horizontal plane and incidence plane, with automatic computation of best direction with eigen vectors of the covariance matrix. Display of linearity and planearity coefficient.

• Evolutive polarization: it is computed on a moving window; you can adjust the window length, the step, and choice many filters.

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Utility Programs

MwP

(june 2007) the moment magnitude calculated on P wave:

MwP is a magnitude calculated from the seismic moment like the 'classical' Mw magnitude introduced by Kanamori in 1977. The Mw magnitude is defined by the relation: Mw = 2/3 (log10Mo – 9.1), where Mo (the scalar seismic moment) is in N.m. Mo is also the largest eigen value of the seismic moment tensor (and the principal strain axis are its eigen vectors). Concerning the relation between Seismic Moment and P wave, it is related by:

U(t,D) = Fp / (4p r a³) G(D)/a M'o I(t), where U is the P wave displacement, Fp is the far field radiation radiation pattern of P wave, r is medium density, a is velocity of P wave, a the earth radius, G includes geometrical spreading and inelastic attenuation and receiver function for a given distance D, M'o and is the time derivative of seismic moment; and at last I(t) is the instrumental response. Thus, from this expression, Mo can be calculated as a function of the integral of the displacement field.

Comparison of MwP versus Mw published by Harvard, for 52 earthquakes from various tectonic regions. Each value of MwP is the average values computed over several stations (at least a ten of stations, until more than 80 stations). All distances are in the [20°, 90°] range. The largest event , Sumatra dec 2004, is largely underestimated (0.6 unit of magnitude). Slow events have also underestimated magnitudes. But, 'normal' (not slow and non giant) earthquakes are correctly estimated.

PPOL_MTPA

PPOL_MTPA is the extension of PPOL in the frequency domain; The spectral analysis is made with the MPTA method (Multi Prolate Taper Analysis). At each frequency, a measure of polarization is calculated, the associated errors bars, the coefficients of polarization and the difference of phase between each components. The best results can be such monitored versus frequency.

PPOL

(Nov 2006)

PPOL (P wave POLarisation) was developed for a study driven by Fabrice R. Fontaine (Research School of Earth Sciences, The Australian National University, fabrice@…). The 3-D character of particle motion of P waves can provide constraints on the upper mantle structure beneath a seismic station (Schulte-Pelkum et al., 2001). Analysis of the deviation of horizontal polarization and the vertical polarization angle as a function of event backazimuth are used to obtain information about:

• sensor misorientation
• seismic anisotropy
• velocity heterogeneities.

The program selects automatically a 40s window around the onset of the P wave, and computes three orthonormal eigenvectors which represents the motion of the P wave in 3-D. The window containing the P wave is calculated from the origin time and coordinates of the hypocenter, using the IASPEI time tables (Kennett and Engdahl, 1991). The rectilinearity of the particle motion must be higher than 0.9 for all observations.

MECA

A tool for viewing beach ball of focal mechanism in text mode

AZI

a simple program to calculate azimuth, back_azimuth and epicentral distance

aziX

A small but useful program for computing azimuth and distance from a simple text list of stations

MM_mag

This is a utility program for calculating the moment magnitude (Mw), the scalar seismic moment (Mo), via the the very robust mantle magnitude (Mm).

SAC2WAVE

An utilty program for converting very easily SAC files into audio file (wav). The sampling frequency of audio files can be changed (typically from 44000 hz to 6250 Hz). The number of channels can be set to 1 (mono) or 2 (stereo) and the signal can be filtered before conversion to audio, to remove noise with a band_pass filter (the order of the filters can be set from 2 to 10) – And the cutt-off frequencies are up to you. Theses parameters are store in a configuration file (sac2wave.ini) to avoid to many arguments to the program.

Seed Response

This program compute instrumental response from response given by SEED response files and IRIS Web site with zeros and poles.

MTPA

Mutli Prolate Taper Analysis is a sophisticated tool for spectral analysis and polarization in the frequency domain.

TIME_FREQX

A tool for computing time_frequency of an entire directory of files (need GMT software http://gmt.soest.hawaii.edu). It runs in a terminal, with the following arguments:

time_freqX FORMAT DIR_IN DIR_OUT SELECT FMIN FMAX WINDOW_LEN_Sec FC-MIN (for High_pass) FC-MAX (for low_pass) Sensor_number (1 2 3 ) DEBIP (0/1)

* FORMAT is SAC_ASCII, SAC_BIN or TIME_FORMAT;
* FREQ_MIN is the minimum frequency in Hz
* FREQ_MAX is the maximum frequency in Hz
* WINDOW_LEN_Sec is the window length in s
* FC-MIN and FC-MAX are the cutt-off frequency in Hz if a band-pass filter must be used.
* sensor_number concerns only the TIME_FORMAT, and corresponds to the sensor (column) number
* DEBIP is a binary value: 0 or 1, to use or not a anti-bip (glitch) function.

the TIME_FORMAT is the format of the tide sensor given by SEA LEVEL FACILITY

http://www.ioc-sealevelmonitoring.org/list.php:

2012-04-02 18:49:00 2.206 6.019
2012-04-02 18:50:00 2.211 5.979
2012-04-02 18:51:00 2.169 5.95
2012-04-02 18:52:00 2.179 5.961
2012-04-02 18:53:00 2.198 5.969
2012-04-02 18:54:00 2.122 5.926
2012-04-02 18:55:00 2.155 5.942
2012-04-02 18:56:00 2.153 5.95
etc.

example of command:

./time_freqX SAC_ASCII /home/dodo/Public/sac_ascii /tmp "PPT_gage_japon*" 0 0.004 7000 0 0 1 0

FFTX

This is a tool for computing various spectral analysis via the Fourier Transform. Several windows taper can be use (or not), like Hanning, Hamming, Blackman, exponantial .., tapers. The output results can be PSD (Power Spectral Density), or Spectral Density, in Linear-Linear or Log-Log representation. Complex spectra, and inverse Fourier Transform can be also calculated. FFTX works with a simple command line in terminal.

The first argument must be the FILE to read in format XY (a simple 2 columns format with the time and values.The other arguments are the process to be executed.

The list of arguments are the following:

usage: fftx FILE_IN -C (Center)
usage: fftx FILE_IN -T (Taper)
usage: fftx FILE_IN -FMIN Freq_min -FMAX Freq_max
usage: fftx FILE_IN -TREND
usage: fftx FILE_IN -POLYFIT Order
usage: fftx FILE_IN -HAMMING
usage: fftx FILE_IN -HANNING
usage: fftx FILE_IN -HANNING_GENE Percent
usage: fftx FILE_IN -BLACKMAN
usage: fftx FILE_IN -BLACKMAN_EXACT
usage: fftx FILE_IN -EXPONANTIEL
usage: fftx FILE_IN -BARTLETT
usage: fftx FILE_IN -PSD Power Spectral Density
usage: fftx FILE_IN -INV_FFT Dt (FFT Inverse)
usage: fftx FILE_IN -COMPLEX
usage: fftx FILE_IN -MOD_PHASE
usage: fftx FILE_IN -LOGLOG
usage: fftx FILE_IN -DSE Densty of Spectral Energy
usage: fftx FILE_IN -Q_EFFECT Dist km U km/s Q
usage: fftx FILE_IN -Q_REMOVE Dist km U km/s Q
usage: fftx FILE_IN -TIME_FORMAT
usage: fftx FILE_IN -SMOOTH_SPECTRUM
usage: fftx FILE_IN -DESPIKE Npt

The resulting spectra are automatically plotted and store in a graphic file as the example given bellow in LOG-LOG.

TS

ts is a tool for testing out practically signal processing; it runs in a terminal with command line.

usage: ts FILE_IN -NG (NO Graphic)
usage: ts FILE_IN -O (OUT file name)
usage: ts FILE_IN -HP Fc order (for High-Pass) -O File_out.xy
usage: ts FILE_IN -LP Fc order (for Low_Pass)
usage: ts FILE_IN -BP FMIN FMAX order (for Band_Pass)
usage: ts FILE_IN -FIR_LP Fc order (for FIR Low Pass)
usage: ts FILE_IN -REJ Fc order (for Rejector)
usage: ts FILE_IN -C (Center)
usage: ts FILE_IN -TAPER percent
usage: ts FILE_IN -INTEGRATOR (Natural)
usage: ts FILE_IN -DERIVATOR (Natural)
usage: ts FILE_IN -IFC (Integrator_FC) Fc
usage: ts FILE_IN -DFC (Derivator_FC) Fc
usage: ts FILE_IN -TREND
usage: ts FILE_IN -POLYFIT Order
usage: ts FILE_IN -COMPENSATOR2 FMIN FMAX
usage: ts FILE_IN -MA npts (Moving Average 3 5 7 or 9)
usage: ts FILE_IN -RAND
usage: ts FILE_IN -LTA a b (Long Time Average)
usage: ts FILE_IN -RMLTA a b (REMOVE Long Time Average)
usage: ts FILE_IN -ADD_CONST a
usage: ts file1 -ADD file2
usage: ts file1 -INTERCOR file2
usage: ts file1 -AUTOCOR
usage: ts file1 -DECAL nber_of_point
usage: ts file1 -FACTOR number
usage: ts file1 -GFORMAT graphic_format
example: ts data.xy -LP 0.05 4 -HP 0.01 0.05 4 -C -TAPER 10
example: ts data.xy -BP 0.01 0.05 4 -C
example: ts data.xy -BP 0.01 0.05 4 -TREND
example: ts dirac_01_Hz.xy -DFC 0.01 -INTEGRATOR -REJ 0.1 2 -GFORMAT pdf

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INSTALLATION

*under Linux/Unix world:
./configure
make
sudo make install

In case of problems with ./configure, just type:

./rebuild.bash

* under WINDOWS:

Just unzip the archive: the executable is inside, with the Utilities Programs

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Environment variables

STK needs 3 environment variables; add them in /etc/profile or in your .profile

#theses 3 ones are necessary for STK: export STK_TMP=/path_to_a_temporary_directory (example /home/Public/Tmp)
export STK_LOG=path_to_a_log_directory_of_your_choice (example~/STK_Log)
export STK_BITE_ORDER=TO_SWAP
or export STK_BITE_ORDER=NO_SWAP (depends on little or big endian order of the processor)

#these 2 ones are optional for STK (but they save time, fingers and mouse)
export STK_SAC_BIN_PATH=/path_where_are_SAC_signals
export STK_SAC_ASCII_PATH=/path_where_are_SAC_ASCII_signals

#could be necessary for non US language
export LC_NUMERIC=en_US.utf-8

Starting Points

• TracGuide -- Built-in Documentation
• The Trac project -- Trac Open Source Project
• Trac FAQ -- Frequently Asked Questions
• TracSupport -- Trac Support
• News?

For a complete list of local wiki pages, see TitleIndex.