Report to the GSL Tech Team, October 20, 2010.
in the context of Earthquake Hazards and
SUMMARY: no big surprises at the trenches of Bailey’s
Lake (just west of
Earthquake hazards and
1. We’re in earthquake territory… global tectonics. LINK USGS dynamic earth
The Basin and Range region of
Using GPS, we can measure relative motion of places on Earth using GPS.
3. We all have our faults… big, little, damaging, not so damaging, obvious, hidden…
Those that matter to management of Great Salt Lake are (a) in the lake (specifically the faults west of Antelope Island and the Promontory Mountains LINK to USGS Baskin image; (b) along the Wasatch fault zone, specifically the Salt Lake segment of the Wasatch fault and the Weber-Davis segment of the Wasatch fault LINK UGS; (c) others (mostly along margins of ranges of Basin and Range because of our setting in the Intermountain Seismic Belt LINK USGS.
Surface rupture: LINK to UGS image of effects … this is why we take all surface evidence of faulting seriously.
Ground shaking: LINK to UGS map showing “worst case” scenario
Tsunami (initial slosh) and continuing seiche: ethical question…
Most risks of the NW quadrant are not
life threatening. The risks are significant and will be costly to address.
However, a highly, very highly unlikely hazard is a killer phenomenon… movement
of the Weber-Davis and/or
Tectonic deformation “tectonic tilt”
(permanent relocation of GSL, Jordan River): LINK:
Changed ground- and surface-water conditions (short- and
long-term): lessons learned from effects of 1983
5. At risk:
More at risk when the lake is at high levels.
Constructed environment… specific to each of the above.
Various: transportation (interstate highways / roads and bridges, rail, airport); industry (dike / impoundment failures); residential infrastructure (sewer, water, gas lines, buried tanks); structures (residential, recreation, utility, communications, other); environmental (secondary, such as ruptured oil/water lines)… and, as yet not constructed, impoundments to “control” the level of GSL (impressive concerns for life safety as well as risk to property).
6. Lines of evidence for hazards and risks
There has not been historic movement of the Wasatch fault;
Utah has many earthquakes LINK to UofU;
There has been movement along faults
near, and perhaps in Great Salt Lake (1909
Geologic records (evidence of landforms/topography;
sediment records (liquefaction, displaced bedding, deposition of sediments); trenching
of faults; geophysical surveys; understanding of fault dynamics.
Bailey’s Lake… is a good example of (a) what can be
studied at most sites with surface rupture, and (b) some of the challenges of
· Setting – fault zones LINK to UGS map
· Site – LINK to UGS image
· Ortho photo of site – LINK to UGS image
· LIDAR image of site – LINK to UGS image
· Fault scarp and site review - LINK to GA photo - scarp
Evidence of faulting (displaced lake-bed layers) – LINK to GA displaced lake beds
Sediments that show change of environment of
· Site review – LINK to draft interpretation