The Double Tree Club Hotel
Directions:
From 55 Fwy South take MacArthur offramp turn right (west). From 55 Fwy North take MacArthur offramp and turn left (west) on to MacArthur. Head west to Main Street and turn left (South). Turn Left on Sandpointe continue through Hutton Center Drive and you are there.
Menu:
Meal includes Caesar Salad, Warm Rolls and main course with Dessert. Coffee and tea are included.
Cost:
$25 for members, $15 for Students and Professors, $30 for non-members, add $5 if reservation is not received by 5pm September 5, 2008.
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Speaker: Dr. Jeffrey A. Johnson
Topic: A Preliminary Case for Secondary
Tectonic Distress in the Epicentral
Region of the M6.7 1994 Northridge
Earthquake
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Abstract:
The 1994 Northridge earthquake occurred on a blind
thrust fault below the San Fernando Valley. The SFV is
an intermontane basin within the convergent Transverse
Ranges. Coseismic rupture, on regional thrusts,
contributes to millimeter level convergence across the
Transverse Ranges west of the San Andreas. Clearly,
with time, the floor of the SFV will deform or continue to
deform as a result of regional convergence. The
question is can a single blind thrust earthquake produce
damaging secondary tectonic distress, at the surface of
a deep alluvial valley, and will future distress occur at the
same location? The answer appears to be a qualified
yes. To better understand the issue street-bystreet
reconnaissance level mapping (≈ 120 km2), of distress
to streets, sidewalks, curbs, etc., was conducted in the
epicentral region of the SFV. The distress was plotted on
1920’s topographic maps, aerial photos from the
Fairchild Collection, Whittier College and color aerial
photos taken shortly after the earthquake. The location
of failed gas and water lines were also collected, from
SoCalGas and the DWP, and plotted. Although subtle,
observed distress locally exacerbated pipeline failures,
may have contributed to fatalities at a Northridge
apartment complex and exhibited some similarities with
distress noted following the 1971 San Fernando
earthquake. Offsets, observed along crack zones, were
one to two orders of magnitude less than the estimated
meter displacements on the primary fault. However,
locally distress appears to correlate with valley floor
geomorphic features suggesting similar distress may
have occurred during prior earthquakes.
Speaker Information:
Jeff Johnson has a B.S. in
Geology from Cal State Northridge, a M.S. in Geology
from UCLA, and a Ph.D. in Engineering from UCLA with
a major in Soil Mechanics and minors in Earthquake
Engineering/Engineering Geology. Jeff is a registered
P.G. and C.E.G. in the state of California. Jeff is a
consultant; his firm is Engineering Geology and Applied
Seismology, out of San Diego. Since 1969 his career
has been divided between research, teaching and
consulting. Research has been devoted to the
understanding of geological and seismic processes and
their potential affects on the performance of engineered
structures. Studies, including the adverse effects of
landslides, subsidence, differential settlement, near
source ground motion, coseismic fault rupture and
associated deformation, and liquefaction have been
conducted in the United States, Central and South
America, the Middle East, and Japan. Current research
includes: (1) the origin and stability of deep-seated
landslides in the complex and seismically active regionalong the bend between the Hayward and Calaveras
faults; (2) the development of criteria for the identification
of seismic exacerbation of cracks in engineered
structures; and (3) the relationship between surface
distress and damage to buried pipelines and coseismic
slip on blind thrusts.
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