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

Last Updated: 5/2007

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.