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Earthquake Directivity Model
Entry ID:
USGS_isodirect
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Summary
Abstract:
Isodirect1 is a MATLAB-language function for modeling seismic directivity at user-selected sites around a user-defined fault. Isodirect1.m implements the Spudich and Chiou (Earthquake Spectra, 2008) directivity model. The results of isodirect1.m should be combined with the ground motion predictions of a non-directive predictive model like any of the four NGA models. Input to isodirect1.m consists of the coordinates of a set of sites where directivity predictions are desired, the coordinates of the corners of one or more fault segments, hypocenter location, earthquake magnitude and slip rake, desired periods for output. Output consists of directivity amplifications for all input sites, plus many intermediate results, such as the points on the fault closest to the input sites, rupture distances, etc.
[Summary provided by the USGS.]
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Related URL
Link:
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GET SOFTWARE PACKAGE
Description:
This package contains MATLAB-language 'main program' isodirect.m, two scripts that call isodirect1.m to calculate predicted directivity for five test cases, and numeric and plotted output from those test cases.
Link:
VIEW RELATED INFORMATION
Description:
Directivity in NGA Earthquake Ground Motions: Analysis Using Isochrone Theory:
We present correction factors that may be applied to the ground motion prediction relations of Abrahamson and Silva, Boore and Atkinson, Campbell and Bozorgnia, and Chiou and Youngs (all in this volume) to model the azimuthally varying distribution of the GMRotI50 component of ground motion (commonly called “directivity”) around earthquakes. Our correction factors may be used for planar or nonplanar faults having any dip or slip rake (faulting mechanism). Our correction factors predict directivity-induced variations of spectral acceleration that are roughly half of the strike-slip variations predicted by Somerville et al. (1997), and use of our factors reduces record-to-record sigma by about 2–20% at 5 sec or greater period.
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ISO Topic Category
GEOSCIENTIFIC INFORMATION
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Distribution Media
Distribution_Media:
Online
Distribution_Size:
15 MB
Fees:
No fees
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Personnel
EARTHQUAKE HAZARDS PROGRAM OFFICE
Role:
TECHNICAL CONTACT
Contact Address:
12201 Sunrise Valley Drive, MS 905
City:
Reston
Province or State:
VA
Postal Code:
20192
Country:
USA
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TYLER
B.
STEVENS
Role:
SERF AUTHOR
Phone:
(301) 614-6898
Fax:
301-614-5268
Email:
Tyler.B.Stevens at nasa.gov
Contact Address:
NASA Goddard Space Flight Center
Global Change Master Directory
City:
Greenbelt
Province or State:
MD
Postal Code:
20771
Country:
USA
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Publications/References
Holt, Rennie S., and Stephaine N. Sexton. Report of a Marine Mammal Survey of
the Eastern Tropical Pacific aboard the Research Vessel David Star Jordan July
28-Dec. 6 1988. 1989. NOAA-TM-NMFS-SWFC-129.
Creation and Review Dates
SERF Creation Date:
2012-02-06
SERF Last Revision Date:
2012-02-07
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