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deep fault error? #143

Open GoogleCodeExporter opened 9 years ago

GoogleCodeExporter commented 9 years ago 
found an error in how EQRM calculates the distances used by some GMPEs.

For deep faults  (i.e. depth > than a fault width) there is a marked offset of 
the area of hazard from the epicentre of the fault. What I think is happening 
is where many GMPEs use the distance from a site to the nearest point of the 
surface projection of the fault (i.e. vertically above the fault) EQRM seems to 
be using the projection of the fault up the fault plane. So for a 45 degree 
dipping fault the surface projection is being horizontally offset by the depth 
of the hypocentre. This suggests to me, that the problem is most likely with 
the function that calculates the Joyner-Boore distance.

I have run tests for six GMPEs and found the error in: 
Atkinson06_bc_boundary_bedrock; Campbell08; Chiou08; and Sadigh_97. 
The error does not appear to be in Somerville09_Non_Cratonic or 
Toro_1997_midcontinent. Though Toro_1997_midcontinent appears to have no depth 
dependency.

Original issue reported on code.google.com by duncan.g...@gmail.com on 11 Mar 2015 at 11:11