West Coast/Alaska Tsunami Warning
Center
Operations Manual
NOAA/NWS/WCATWC
910 South Felton Street
Palmer, Alaska 99645
http://wcatwc.arh.noaa.gov
Section
4.1.11 – mtinver
Date Written: 8/2004
Development Language: MicroSoft
C/C++ v7.0 using WinAPI
Necessary Rings:
Input Ring - WAVE_RING_LP;
reads TYPE_TRACEBUF format messages
Input
Ring - HYPO_RING; reads TYPE_HYPOTWC format messages
Necessary Data Files:
StaFile
- picker configuration file
StaDataFile - seismometer
location, elevation, etc.
DummyFile
- Hypo-parameters of last located quake
ResponseFile - Broadband instrument
response in poles/zeroes format
MTFile
– Results file
EmailFile
– Results file to send
DepthFile
– Maximum expected quake depth file
EBPTimeFile
– Observed P-Times file
Initialization File:
mtinver.d - read on
module start-up
Module Description:
This module determines moment tensor solutions from teleseismic broadband
seismic data by inverting the first 200s of data. The technique was provided to the WC/ATWC by USGS,
and converted to an earthworm module which reads data from a WAVE_RING, or from
files created by disk_wcatwc. Observed
data are compared to synthetic data to determine the most likely moment
tensor. Green’s functions provided by USGS
are used to generate the synthetic seismograms.
Trace data are only used for stations with observed p-times (taken from
automatic p-picks or interactive p-picks).
The synthetics are shifted up to a specified amount of time to account
for bad p-picks. Synthetic seismograms
are created for depths up to the maximum expected depth of the epicentral
region. Moment tensors, scalar moment
magnitude, focal plane solution, and depth are output. An epicenter must be provided to the module. The data and synthetics are filtered based on
the first seismic moment estimate. Lower
frequency filters are used for larger earthquakes.
Input seismic data is taken from WAVE_RING_LP. The data is buffered by this
module. Processing is triggered by a TYPE_HYPOTWC message obtained from the
HYPO_RING. If the hypocenter has a magnitude greater than 5.0 Mb, Ml, or Mwp,
this module will compute a moment tensor every one minute from 11 minutes after
the origin to 25 minutes after. Several checks are made on the data, including
signal-to-noise, gaps checks, and DC offset removal.
Data are saved for up to MinutesInBuff time, so processing can be performed for
a quake so long as the data are still in the buffer. The processing is either
triggered automatically through the HYPO_RING, or manually in this module through
a menu option.
Program Controls:
This module has a Windows graphical interface.
Due to this interface, the module will only compile and run under Windows (NT,
2K, or XP). The display shows a beachball and source parameters on the left,
and comparisons between the observed signal and synthetic on the right.
Mouse Buttons:
No effect.
Menu
Options:
Inversion:
Compute MT: Using
last location in dummy file, process broadband data for moment tensor inversion.
Several control parameters can be
interactively set in the follow-up dialog box.
Stop
Processing: Stop
ongoing computations.
Waveform Display:
Green’s functions: Display original
Green’s functions for a distance/depth.
Synthetics: Display
the results for the last compute moment tensor.
Refresh: Re-paint the screen.
