mathematical formulation of the probabilistic model,
of seismic source zones developed for the EUS is
are described in Appendix E.
Examples of the
described in Appendix E, Paragraph E-5c.
development of site-specific ground motions using
PSHA methodology are also presented in Appendix
E. Guidance and computer programs for PSHA are
also described in Navy publications TR-2016-SHR
and TR-2076-SHR (Ferritto, 1994, 1997).
e.
Characterizing Earthquake Sources.
(1) Source identification. Seismic sources are
identified on the basis of geological, seismological,
and geophysical studies.
In the western United
States (WUS), i.e., west of the Rocky Mountains)
major seismic sources include active faults that have
been identified on the basis of surface and subsurface
evidence.
For example, major active faults in
California are shown in map view in Figure 3-5. An
example of faults mapped in a localized region of the
western U.S. (San Francisco Bay area) is shown in
Appendix E, Figure E-10. In some coastal regions
of the WUS, specifically northwest California,
Oregon, Washington, and southern Alaska, major
earthquake sources also include subduction zones,
which are regions where a tectonic plate of the
earth' crust is thrusting beneath an adjacent tectonic
s
plate.
For example, a cross section through the
subduction zone in the Puget Sound area of
Washington is shown in Figure 3-6. In the eastern
U.S. (EUS), earthquake faults typically do not have
surface expression, and their subsurface location is
usually
not
precisely
known.
Accordingly,
earthquake
sources
in
the
EUS
are
usually
characterized as zones with the zone boundaries
selected on the basis of boundaries of geologic
structures and/or patterns of seismicity. An example
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