4. VALUE OF THE REPORT
Prior to publication of this report, several agencies have requested data from
us or asked for assistance in interpreting our findings for engineering or
surveying purposes. Briefly, these include the following:
- The National Geodetic Survey has so far received and filled about 100
requests for new heights and coordinates in southern California from the
restored network.
- Caltrans used the pre- and post-earthquake elevation changes to assess
subsidence and deformation associated with tunneling for the Metropolitan
Transit Authority's subway extension
[Satalich,
1996].
Such use of the restored network will continue as the MTA expands, and thus the
restored leveling network promises to improve the safety of the drilling
operations.
- NASA's Jet Propulsion Laboratory has requested and received our map of
long-term subsidence in metropolitan Los Angeles to evaluate and interpret
deformation inferred from a new generation of radar satellites, which measure
height change by forming an interferogram with three successive radar images of
the topography
[e.g., Massonnet, et al., 1993].
- The City of Simi Valley has used the anomalous BM listing and the sites
of liquefaction and landslides to assess damage and urban reconstruction
issues. The U.S. Geological Survey prepared a set of deformation profiles and
maps with the surface street grid included at their request, which aided the
Simi Valley deliberations.
- The California Seismic Safety Commission requested and received a
preliminary version of the map to compare elevation change measured by
surveying with the distribution of ground cracking mapped by its members and
independent geologists. The Commission seeks to evaluate the extent and cost of
damage to the built environment directly attributable to surface faulting in a
blind earthquake.
- Scientists at the U.S. Geological Survey and the California Institute of
Technology used the coseismic elevation changes developed in this report to
study the earthquake source and rupture propagation. This effort has lead to
improved models of earthquake hazards, and a better understanding of the causes
of earthquake shaking
[Wald,
Heaton, & Hudnut, 1996].
- Geologists at the U.S. Geological Survey are using the coseismic
elevation changes along with detailed surface mapping to determine if ground
cracks in the Granada Hills were caused by slip on a fault or by shaking and
liquefaction.
U.S. Department of the Interior |
U.S. Geological Survey