Rapid Pd Magnitude
http://akshield.pbworks.com/w/page/77591672/UW%20Rapid%20Pd%20Magnitude
Description
The Rapid Pd Magnitude is a low accuracy estimate of the earthquake magnitude that is critical for verification of magnitudes for large
earthquakes greater than about Mw 7.0. It is derived from the first 4 sites where GPS and accelerometers are simultaneously available.
The magnitude estimate becomes progressively more accurate as more GPS-accelerometer sites are triggered by the earthquake
wave.
Use for Decision Making
Initial earthquake alerts provided by the National Earthquake Information Center and the NOAA Pacific Tsunami Warning Centers are
based on seismic instruments that do not reliably distinguish the earthquake magnitude for earthquakes in the range Mw 7.0 to Mw 9.5.
The Rapid Pd Magnitude should be used to assess whether or not the initial earthquake estimate could be significantly
underestimated. It is useful for automated systems that are initiated when a threshold magnitude is exceeded, and can be used for
early warning prior to the arrival of damaging S-wave energy.
Data Availability
Within about 15 seconds of the start of the earthquake rupture for the case of the AK Shield event. In general the time delay depends
on the distance of the closest 4 sites to the epicenter.
Product Text
The 1964 Alaska Exercise scenario earthquake Pd Magnitude Update
Time: OT + 15 seconds
Number of stations reporting: 4
Magnitude Update: 10.0
Accuracy: Low
Threshold: Confirmed Magnitude greater than 8.0 with 90% confidence
Rapid Pd Magnitude from combined
GPS and accelerometer displacements.
Diagonal lines indicate earthquake
magnitude. The yellow points show the
amplitude of the earthquake wave arrival at
each GPS site. The yellow points fall in the
range between the Magnitude 8.0 and
Magnitude 9.5 confirming even with the first
stations that are reporting that a major
earthquake of magnitude 8.0 is underway
Download the Product:
 Alert text message
Contact Information
 University of Washington; Points of Contact: Brendan Crowell, crowellb@uw.edu
Scientific Reference:
Crowell, B. W., D. Melgar, Y. Bock, J. S. Haase, and J. Geng (2013), Earthquake magnitude scaling using seismogeodetic data,
Geophys. Res. Lett., 40, 6089–6094, doi:10.1002/2013GL058391.