West Coast/Alaska Tsunami Warning
Center
Operations Manual
NOAA/NWS/WCATWC
910 South Felton Street
Palmer, Alaska 99645
http://wcatwc.arh.noaa.gov
Section
4.1.10 – mm
Date Written: 1/2002
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
RegionFile - Mm path correction file
MwFile - Mw results file
Initialization File:
mm.d - read on
module start-up
Module Description:
This module determines moment magnitude from broadband seismic data. The
magnitude scheme (Mm) used at the French
Polynesian Tsunami
Center is used to determine
Mm (Mw). This was developed by Okal, Talandier, and others from the French Polynesian
center. The original code was provided by Weinstein of PTWC. At the WC/ATWC it
was converted to this earthworm module.
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 expected Rayleigh wave times at stations listed in
StaFile and will evaluate the data in the window for Mw. The Mw is computed 12
minutes after expected Rayleigh wave arrival time based on peak spectral
amplitude and Rayleigh wave path. No signal-to-noise checking is performed.
Data is saved for up to MinutesInBuffer time, so processing can be performed
for a quake so long as the data is still in the buffer. A semaphore is set up
here (similar to lpproc) that can be set in the program LOCATE to trigger
processing. LOCATE does not have to be running for this code to work. The
processing is either triggered automatically through the HYPO_RING, manually in
LOCATE, or manually here through a menu option.
Output from this module is written to MwFile and to a window. Module
hypo_display and program LOCATE access MwFile.
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 list of computed Mws on the left and spectral
displays for chosen stations on the right. As magnitudes are computed, the
average Mw will be displayed in the title bar.
Double-clicking a station name in the list box will select that station for
spectral display on the right. If no interaction is made, the last 6 stations
for which Mw was computed will be displayed on the right.
Mouse Buttons:
Left button on station in list
will bring up spectral display for that station.
Menu
Options:
Magnitudes:
Compute
Mm: Using last location in dummy file, process broadband data for Mm.
Stop
Processing: Stop
ongoing computations (usually used when automatic location has been updated).
Refresh: Re-paint the screen.