Hello Don,

I looked at this possibilty about a year ago. The biggest problem is the sweep of uncertainty in years for the seismic events. I would think that a seismologist could ascertain if a rupture occurred during an inundation sequence in a trans-tensional basin like this. In other words, would the trenching analysis show some kind of H2O penetration versus a period of lake dissication? This was just a brief look at the possibility. I have not done further study since last year. Again, my biggest question was if anybody had noticed and done further work on it. No sense in reinvented the wheel. Your comments and knowledge are always appreciated..

Glen

May 1, 2005
LAKE CAHUILLA
Earthquakes Caused by Basin Loading?

With the current interest in the Coachella Segment of the San Andreas Fault, I thought I would mention a hypothesis that I have been working on for a while. This has to do with the historicity of large ruptures along the Coachella Segment of the San Andreas Fault and the loading and unloading of the Salton Trough by ephemeral stands of water. It appears that the dessication and inundation of the lake coincide with large seismic events in that region. My biggest question is if anybody else has noticed this, or has done any further study on the plausibility of such a coincidence.

As early as 1963, I noticed the water line from Hwy 86 between Salton City and Indio on the east side of Toro Peak and the mountains of the southern San Jacinto. This water line is clearly visible, and denotes the demarcation of the highest water stand of Lake Cahuilla.

The Events

First Lakestand
AD 700 to 940, full dessication
Seismic Event
AD 825 (+65, -55) (Fumal and others)****

Second Lakestand
AD 940 to 1210, full dessication
Seismic Event
1231 AD (+59, -61 yrs); 983 AD (+168, -142 yrs) (Fumal and others)****
1020 AD (±20 yrs) (Sieh, 1986)

Third Lakestand
A.D. 1210, with a partial recession to about -130 feet below sea level at about A.D. 1430.
Seismic Event
1231 AD (+59, -61 yrs) (Fumal)****
1300 AD (±90 yrs) (Sieh)

Fourth Lakestand
A.D. 1430 to 1540 based on sedimentation and evaporation rates
Seismic Event
1502 AD (±52 yrs) (Fumal)
1450 AD (±150 yrs) (Sieh)****

Fifth Lakestand
A.D. 1516 and 1659 (Schaefer 1994) Partial filling
Seismic Event
1676 AD (+35, -156 yrs) (Fumal)
1680 AD (±40 yrs) (Sieh)****

Sixth Lakestand, Man Created> the Salton Sea
No Major ruptures since 1680 AD

REFERENCES

http://qfaults.cr.usgs.gov/faults/FMPro?-db=us%20web%20fault%20database.fp5&-format=record3%5fdetail.htm&-lay=scientist%20input&-sortfield=name&-op=cn&namesearch=san%20andreas&Statesearch=California&-max=10&-recid=34703&-find=

Recurence Interval ( for seismic ruptures)

150- 300 yrs (late Holocene)

Comments: Sieh (1986 #5777) identified at least four major slip events between 1000 AD and 1700 AD at the Indio site [1j-3]. The event dates, based on 14C dates of fluvial and lacustrine deposits, are 1680 AD (±40 yrs), 1450 AD (±150 yrs), 1300 AD (±90 yrs), and 1020 AD (±20 yrs). The Working Group on California Earthquake Probabilities (1995 #4945) used data reported in Sieh (1986 #5777) to calculate an average recurrence interval of 220±13 yrs. At the Thousand Palms Oasis site [1j-1] at least 4 and probably 5 large earthquakes have occurred between AD 800 and AD 1700 (Fumal and others, 2002 #5726). Fumal and others (2002 #5726) reported a preferred average recurrence interval of 215±25 yrs. Event dates at the Thousand Palms Oasis site [1j-1] are 1676 AD (+35, -156 yrs), 1502 AD (±52 yrs); 1231 AD (+59, -61 yrs); 983 AD (+168, -142 yrs), and 825 AD (+65, -55 yrs).

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Web Site; (Long but interesting archeological article)

http://gis.esri.com/library/userconf/proc00/professional/papers/PAP377/p377.htm

Prepared by: James H. Cleland, Andrew York, and Angela Johnson
KEA Environmental, Inc., San Diego, California

The most widely accepted chronology for the stands of Lake Cahuilla (Waters 1983) identifies a series of four lakestands occurring over the past 1,500 years (Figure 3). The first is thought to have begun at about A.D. 700 and ended around A.D. 940, with full desiccation. The second interval is not directly dated but based on estimated sedimentation and evaporation rates is inferred to have occurred sometime between A.D. 940 and 1210, again with complete desiccation. The third interval is thought to have begun around A.D. 1210, with a partial recession to about -130 feet below sea level at about A.D. 1430. At this time the lake began to fill again, initiating the fourth interval; this interval is estimated to have terminated around A.D. 1540 based on sedimentation and evaporation rates, as well as the lack of any direct observation of the lake by Spanish explorers traveling through the area after that time. More recently, a fifth interval has been proposed based on archaeological data from a site on a recessional shoreline. This is believed to have been a partial infilling occurring sometime between A.D. 1516 and 1659 (Schaefer 1994).