SDAG Monthly Meeting
Wednesday - February 19 |
Location:
Tom Hams Lighthouse
2150 Harbor Island Drive
San Diego, CA 92106
(619)291-9110
Directions:
Head toward San Diego International Airport. Turn on to Harbor Island Drive. Turn right and go to the end of the island.
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6:00pm -
Social hour
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SDAG Monthly Meeting
6:00pm - Happy Hour
7:00pm - Dinner
8:00pm - Program
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7:00pm
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Menu: Grilled Petite Top Sirloin / Vegetarian Penne Pasta
if pre-registered by the deadline, $5 extra if you did not make a reservation.
Click the SDAG member checkbox on the reservation form if you are a member.
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Cost: $ 65.00 Member; Non-Member $ 75.00; Student $ 30.00
Reservations:
Make/Pay your reservation online by clicking the button below
by Noon Sunday, February 9
RESERVATIONS CANNOT BE ACCEPTED AFTER by Noon Sunday, February 9
(Please note beginning January 2024 all meeting reservations will require on-line pre-payment due to venue costs,
venue contracts, and loss of money due to no shows.)
IF YOU DO NOT PRE-PAY YOUR FOOD RESERVATION, WE CANNOT GUARANTEE YOU A MEAL.
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8:00pm - Program
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"A New Seismotectonic Framework for Active Faults in Metropolitan San Diego"
Speaker: Dr. Karl Mueller, Professor of Geology, University of Colorado, Boulder
This talk presents evidence for a recently recognized active right lateral
fault system and two extensional stepovers that extend from Poway, CA
to Ensenada, Mexico. Mapping of structures using digital elevation
models derived from pre-urbanization (1953) air photos and visualization
of faults and folds using 3D mapping of contacts suggests the fault
system connects the La Nacion Fault Zone (LNFZ) and Salsipuedes
faults with three, newly recognized fault segments. These include a right
lateral fault that extends the LNFZ 23 km north from a small, 4 km wide
pull-apart basin in Allied Gardens, an 8 km long normal fault along the
US Border, and a 15+ km long, right lateral fault and splays in Imperial
Beach. Scarps along the border offset the Tijuana River floodplain and
mark the surface trace of a large listric normal fault, or detachment that
extends north beneath much of San Diego. Folding of the hanging wall
(i.e., a rollover) above the curved detachment has formed an extensional
half graben, the primary structure that drives subsidence in San Diego
Bay. The surface expression of the rollover is best defined by the south-
tilted flight of terraces south of Mission Valley. Bending moment faults at
the crest of the rollover have formed an axial graben (Mission Valley) that
is marked by faceted spurs and an offset fluvial terrace at the I-15.
Progressive folding of Eocene and Pleistocene strata across the Mission
Valley axial graben and synextensional Pliocene fill in the San Diego pull-
apart basin suggests the LNFZ likely slips at less than 0.5 mm/yr. The
Salsipuedes fault extends north from the coast along Baja into Imperial
Beach and along the Silver Strand where it is marked by pressure ridges
and scarps to the east, similar to faults defined by seismic reflection
profiles in San Diego Bay. This fault represents a plausible continuation
of the Rose Canyon fault that may be linked with the Salsipuedes. The
small pull-apart basin in Allied Gardens is defined by steeply dipping
fault strands that form a positive flower structure exposed on the face of
the large rock quarry along the San Diego River. An associated pressure
ridge deforms Eocene strata and deflects stream channels in Tierra
Santa that marks the newly recognized right lateral fault segment that
extends the LNFZ 23 km north to Poway. Faults in the pull-apart basin
deform early Pleistocene terraces in a small rollover into the San Diego
River channel that creates another axial graben at its crest (Alvarado
Canyon). The drop in base level in the Allied Gardens pull-apart is
recorded by dramatic stream channel incision and steepened hillslopes,
leading to the development of cliff faces in Mission Gorge. The surprising
discovery of a seismically active fault system in a densely urbanized city
of 3M inhabitants was aided by improved methods for visualizing a lidar-
scale DEM made from 1953 air photos and structure contour maps of
stratigraphic contacts extracted from geologic maps.
Karl Mueller is a professor of Geology in the Department of Earth and
Science at the University of Colorado, Boulder. A native of San Diego,
Karl first earned degrees in Geology at SDSU, working with Tom
Rockwell (MSc, '84) on the Laguna Salada Fault. His subsequent time
in the oil industry included work on gravity-driven extensional
structures in the Gulf of Mexico and a PhD on upper crustal extension
in a metamorphic core complex in NE Nevada. These were followed by
a postdoc at Princeton working on active blind thrusts in southern
California. Karl then teamed up with Tom Rockwell to determine how
and why far-field uplift occurs in Southern California and Baja, leading
to the rift flank model for marine terrace uplift in coastal San Diego.
Other projects included studies of active blind thrusts in Japan, the
New Madrid seismic zone, Taiwan, and Utah, exploring how erosion
might affect active faulting. Karl has also worked on blind thrusts on
Mars and Mercury and their implications for early heat loss on these
planets. Karl is now focused on developing new techniques for
identifying subtle, slowly slipping active faults in the densely urbanized
landscape of San Diego.
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Upcoming SDAG meetings - 2025
March 19 - Don Barrie on New Zealand Geology
April 16 - Student research presentations by student scholarship recipients
May 21 - TBA
June 18 - SDAG / SCGS Joint Meeting
July 16 - TBA
August 20 - Dr. Mario Caputo on Sedimentary Rocks in the Grand Canyon
September 26-28 - SDAG Annual Field Trip, San Andreas Fault in the Wrightwood area, Transverse Ranges (no meeting this month)
October 15 - Todd Wirth on “First report of marine invertebrate megafossils from the Eocene Mount Soledad Fm at Tourmaline Surfing Park”
November 19 - Joint Meeting with AEG Inland Empire Section
December 17 - Traditional Holiday Celebration at the San Diego Natural History Museum with Tom Deméré
Recordings of past meetings
Note: If the video or sound does not play, try using another web browser. Firefox and Chrome may work on some of the videos. MS Edge and Safari are most likely to work.
8/21/2024 Upper Cretaceous through lower Eocene strata in San Diego: Messages for the end-Cretaceous impact, extinctions, and paleoclimates - Dr. Pat Abbott
5/15/2024 Exploring Iceland's Geological Wonders: From a Regional Perspective to a Hiking Expedition - Don Barrie & William Buckley
3/19/2024 Mighty Bad Land: A Perilous Expedition to Antarctica Reveals Clues to an Eighth Continent - Bruce Luyendyk
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2025 SDAG Secretary.
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