Forecast vs' Prediction

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ESS 8 - Earthquakes - Week 9
Prof. Didier Sornette TAs Sara Cina and
Jelena Tomic
Shock Waves Through Los AngelesThe Northridge
Earthquake
http//www.ess.ucla.edu/academics/courses/web/fall
_2005/ess_8/index.asp
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Plan

• Dangers of living in fault zone
• Where are the faults
• How zoning relates to faults
• Landslides

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Puente Hills Thrust Fault System
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"We are currently in a seismic lull that has
lasted at least since the first Europeans
arrived here more than 200 years ago," Dolan
said, "and that can't last forever."
http//www.scec.org/research/030404dolan.html
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All known big faults in SoCal
Most faults have longer repeat times than San
Andreas
SCEC web page
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How close is dangerous?

• Magnitude of quake is the most important factor
• Also construction quality
• And softness of ground
• On the fault is a special problem
• Danger is sum of all active faults
• Most dangerous when many nearby faults are
  active, like LA and Bay areas

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Fault zone

• Width
• Legal definition for Special Studies Zone
• 220 m on either side of mapped fault trace
• Physical definition depends on how active and
  well-developed the fault is
• Width of San Andreas fault zone 1-2 km
• Significance few structures can withstand ground
  rupture

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Hazards of faulting

• Generally, quake hazard is from ground shaking
• But ground shift (rupture) can be devastating
  right on fault trace
• Greater ground shift and ground shaking in fault
  zone

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Fault scarp in Armenia, 1988
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Faulting damages buildings

• Foundations are cracked and thrust apart
• Vertical supports collapse or are knocked askew
• Floors and roofs sag or fall
• Thus, building can be torn apart

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Example from Nicaragua

• 4-story building on the fault
• Reinforced concrete structure
• Just 20 cm of fault offset
• Building pancaked

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Building on fault
Yanev, p. 29
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Artists renditionof house torn in two
Yanev, p.30
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Normalfaulting
San Fernando Yanev, p. 31
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Damageinside
(Uninhabitable, a different house)
Yanev, p. 31
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Ominous furrowsafter San Fernando quake
Yanev, p. 30
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1959quakeinIdaho
Mighty scarp
EQ engineering 205
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Idaho destruction
Flat house
Scarp
Yanev, p. 30,
EQ Eng. 208
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Where are faults, exactly?

• Alaska
• Oregon, Washington, British Columbia
• California
• Wasatch Fault Zone

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Alaska

• Most dangerous in US
• 8 quakes over M8 in last 90 years
• Main fault is subduction thrust
• Only surfaces on ocean floor
• Many secondary faults
• Sparsely populated
• Also has volcanoes, tsunamis

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1899-1979 Alaska quakes
Stars - M gt 7.5 Triangles - 6.5 to 7.5
Yanev, p. 175
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Oregon-Washington

• M 9 every 1000 years, last in 1700
• Recent quakes
• M 6.5 in 1965 in Seattle
• M 7.1 in 1949 in Olympia
• Main fault is subduction zone
• Also volcanoes (like Mt. St. Helens)
• Not adequately prepared
• Weve looked at these faults before

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PacificNorthwest
Iacopi, 27
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California

• Last 150 years, 2 or 3 quakes of M8
• Main fault is strike-slip, on land
• San Andreas fault zone
• Easy to map in detail
• Many secondary faults
• Some offshore, some farther East
• Weve talked about these faults already

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Carizzo

• San Andreas Fault zone in the Carrizo Plains

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Officialfaults
San Andreas, Garlock, SoCal and Bay Area branches
Yanev, p. 42
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Northern California

• San Andreas
• Runs through Point Arena, Point Reyes, San
  Francisco, San Jose, Watsonville
• East Bay Faults
• Calaveras-Hayward-Rodgers Creek
• Some farther east
• Offshore faults?

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BayAreafaults
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Southern California

• San Andreas
• Runs 30 km north of LA, thru San Bernadino, Palm
  Springs, Salton Sea, into Mexico
• Faults under LA are hard to find
• Mostly not strike-slip
• Surface reworked by civilization
• LA to San Diego - system of faults
• SAF, San Jacinto, Elsinore faults

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LA regional faults
Yanev, 195
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Los Angeles faults
Keller, 4-2
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Faults across Los Angeles
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Geologists cross-section
Arvid Johnson
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Newport-Inglewoodand hospitals
Yanev, 33
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San Andreas near LA
Yanev, 187
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San Andreas meets I5at Tejon Pass
Iacopi, 48
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Northern LA faults
Yanev, 193
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Faults in San Bernardino
Yanev, 191
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Faultssouthof LA
Yanev, 187
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Rest of US

• Wasatch fault zone
• Utah, Idaho, Montana, Wyoming
• About 10-25 as active as San Andreas
• Mainly normal faults
• New Madrid
• Had some big quakes
• We dont know how often they strike
• Charleston, plus a few others

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Wasatchfaultzone
Yanev, 203
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National map of quakes
Subduction
Wasatch
New Madrid
Mostly small events
San Andreas
Rio Grande Rift
Yanev, 208
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Examples of problems

• Zoning
• Daly City
• Old laws not very good
• Hayward fault
• Old laws not very good
• Salt Lake City
• No laws
• San Fernando
• What were they thinking?

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Daly City

• Zoning ignores the presence of the fault

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Daly City1956
Yanev, 34
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Daly City in 1966
Yanev, 34
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Bad neighborhood plan
Hayward Fault Yanev, 44
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Better neighborhood plan
Hayward Fault Yanev, 44
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Bad building site
Fault trace
Yanev, 45
Salt Lake City
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Bad building site? Yes
San Fernando, 1972
Yanev, p. 45
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Avoid living in fault zone

• Should be zoned for parks
• Or, at a minimum, roadways
• It's best to live 5 miles or more away from
  faults
• Often unrealistic
• Even creeping faults are bad news

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How strong will the shaking be? The
importance of the site

• The strength of shaking depends on
• Earthquake size
• Distance to epicenter (actually to region of
  large slip)
• also focusing or defocusing that may occur along
  the path from source to site
• Site
• nature of the ground just under the structure

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Hazards of various geological foundations

• Soft soils - stronger shaking
• Wet soils - liquefaction potential, landsliding
  potential
• Cliffs and ridges - stronger shaking, landsliding
  potential

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Soft Sites

• Stronger shaking on
• Soft soil
• Landfill
• Waterside sites
• Seismic waves grow in amplitude when they pass
  from rock into less rigid material such as soil
• Soils behave like jelly in a bowl, which shakes
  much more than the plate

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Soft vs. hard sites

• Two quakes
• 1906 San Francisco
• 1989 Loma Prieta
• Hills of San Francisco and Santa Cruz Mts felt
  moderate motions
• But damage was concentrated in
• Soft and deep soil sites
• Especially landfill

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Soft ground deforms
Yanev 49
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Makes skewed streets
Yanev 49
1906 SF scene
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Soft ground causes trouble
Missing story
Yanev 49
1989 Loma Prieta
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Influence of soft ground

• Softness can vary on a fine scale
• Old filled stream beds
• Sand dunes
• Water-saturated muds
• Motion can vary by factor of 4 in 100 m
• 1906, near-surface geology mattered
• Santa Rosa and San Jose as hard hit as SF due to
  soft ground downtown

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Bay Areasoilconditions
Keller, 4-14
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1906 SF damage pattern
Yanev 50
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1906 damage in Santa Rosa
Iacopi 91
City Hall
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1906 SF settling
Yanev 53
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LA shaking pattern
Yanev 52
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More on soft ground

• Mexico City badly damaged in 1985
• Quake more than 200 miles away
• Extremely soft soil downtown
• Soft sites common
• LA, Bay Area, Seattle, Salt Lake City, Anchorage,
  Boston, New Orleans ...

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High-rise buildingMexico City, 1985
Keller, 4-13
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Destruction of subway in Kobe, Japan
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Soil Liquefaction

• Liquefaction compaction of water-saturated soil
  during intense shaking allows water to flow
  upward and the soil loses its shear strength and
  flows, becoming liquefied into a kind of
  quicksand
• Liquefaction strikes soft, sandy water-saturated
  soils
• Usually low-lying and flat
• Buildings may tilt or sink into liquefied
  sediments tanks may float

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Liquefaction during 1995 earthquake Kobe, Japan
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More liquefaction
Watsonville, 1906
Kovach, 3-9
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Sinking in quick sandin Niigata 1964
EQ Eng 230
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Rising sewage tank
EQ Eng 230
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TiltingbuildingsinNiigata
EQ Eng 232
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Niigata 1964
Yanev 55
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Landfills

• Often poorly compacted material that often
  decays, producing voids and weak soils
• Therefore
• Strong shaking in earthquake
• Ground can settle substantially
• Newer landfill better compacted, but may still
  have problems in large quake
• Often impossible to detect
• Pre-WWII methods often leave voids
• Clues
• Sidewalk cracks, misalignment of adjacent
  buildings, doors, or windows can be clues

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Tilting buildings
Differential settlement
Yanev 56, 58
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Riverbanks

• Riverbanks are often thick layers of soft, silty
  clay with a lot of water
• Same problems for edges of bays and soil under
  levees
• Many downtowns are on riverbanks
• Riverbank towns often have old buildings

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Riverbank collapse
River
Yanev 59
Salinas River in 1906
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Waterside Sites

• Like riverside sites
• Soft soils, so stronger shaking
• Alluvial soils clay and sand, often build up to
  very thick layers
• Wet soils, so high liquefaction potential
• Many roadways, railways, pipelines along the water

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Roadwaycollapse
Road through Portage, AK in 1964
Iacopi, 19
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Liquefaction in1989 Loma Prieta EQ under Highway
1 near Watsonville
Riverbed
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Liquefaction damage at Hyogo Port, Kobe , Japan
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Liquefaction damage on landfill at Port Island,
Kobe, Japan
Notice seaward slump
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Disruption of hydrofoil service, Kobe, Japan
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Cliffs and Ridges

• Experience greater shaking because unsupported by
  ground and rock on one or both sides
• As waves emerge from ground, they are reflected
  back from cliff face and cause further
  amplification of shaking
• Energy trapped within peak of the ridge
• Example Glenridge, Bel Air
• Landslide and rockfall potential

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Steep cliff

• Landslide,
• Kobe Japan

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But hills can be okay

• Generally, it is better to be on hard rock in
  mountains than on a soft basin, despite some
  amplification from cliffs and ridges.
• Examples
• Santa Monica Mts. did OK in Northridge
• Santa Cruz Mts. had some problems in Loma Prieta
• But mainly due to bad construction

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Tagged buildings after Northridge Earthquake,
1994
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Demonstration of focusing effect by a
curved Interface between two different layers
P. Davis
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GAO S LIU H DAVIS PM KNOPOFF L. LOCALIZED
AMPLIFICATION OF SEISMIC WAVES AND CORRELATION
WITH DAMAGE DUE TO THE NORTHRIDGE EARTHQUAKE -
EVIDENCE FOR FOCUSING IN SANTA MONICA. BULLETIN
OF THE SEISMOLOGICAL SOCIETY OF AMERICA, 1996
FEB, V86 N1S209-S230.
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Landslides

• Landslide a chunk of ground, usually wet and
  weak, breaks loose, then slides down hill
• Earthquakes often trigger landslides
• Landslide most common on hillsides, steep slopes
• From both natural and man-made causes
• Seasonal problem, worst after heavy rains
• Luckily, Loma Prieta, San Fernando, and
  Northridge struck in dry weather
• San Fernando (Northridge) earthquake
• Even in dry season, caused 1000 (10000)
  landslides, with 50 feet of sliding

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Landslide schematic
Keller, 7-3
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Kinds of slides

• Landslides
• Mud slides
• Debris flows (volcanoes)
• Rock falls
• Generic landslides
• Snow and Ice
• Avalanches
• First well look at slow slides

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Earthflow
Australia, also visible along Hwy 5
NOAA slides
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Pacific Palisades slumps
NOAA slides
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Glen Canyon talus cones
NOAA slides
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Swiss slump
NOAA slides
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Big slide
1906, Frank, Alberta, over in 2 minutes, buried a
whole town
NOAA slides
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LandslidePeru, 1970due to quake,60,000
killed,16 km slide,4 km drop,with glacial ice
Before
After
Keller, 13-9
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Path ofPeru slide


Picture in previous figure
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In 1970, an earthquake-induced rock and snow
avalanche on Mt. Huascaran, Peru, buried the
towns of Yungay and Ranrahirca. The total death
toll was 66,700. The avalanche started with a
sliding mass of glacial ice and rock about 909 m
(3,000 ft) wide and 1.6 km (1 mi) long that swept
downslope about 14.4 km (9 mi) to Yungay at an
average speed of over 160 km (100 mi) an hour.
Ice picked up morainal material and by the time
the mass reached Yungay, it is estimated to have
consisted of about 2,200,000 m3 (80,000,000 ft3)
of water, mud, and rocks.
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Translational landslide about 30 - 40 meters deep
that blocked a valley in March - April, 1973. The
slide occurred in Neogene molasses on the
southern slope of Blidisel Hill in the Buzau
Subcarpathians. The slide was reactivated during
the March 4, 1977 earthquake in the eastern
Carpathians. Photograph Credit Dr. Dan
Balteanu, Romanian Academy.
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Slides major California problem

• Rapid tectonics
• Particularly fast-rising mountains
• Ample rain for lubrication
• Coast heavily built-up
• Presence of quakes

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Californiatroublesin 1997-98
Cities with slides are red
Next figure
http//geology.wr.usgs.gov/wgmt/elnino
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Example San MateoCountyslides
San Fran
The Bay
Daly City
Red areas have slid
San Jose
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MoreproblemsforDaly City
Davidson, 15-9
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The Blackhawk landslide (17kyrs BP)
5 miles
2 miles
Certainly the largest slide in the Transverse
Range province is the Blackhawk, on the north
slope of the San Bernardino Mountains This
prehistoric slide is one of the largest known in
North America. It was studied in detail by R. L.
Shreve, who showed that the slide moved to it's
resting place on a cushion of compressed air.
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Southern California mess
Tarbucks, 3-23
Made worse by loss of vegetation
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A slide at night

• Castle Rock Road, in Laguna Canyon
• February 23, 1998
• Heavy rains
• A dozen small soil slips converged
• Powerful enough to take some houses for a ride
• Typical hillside in a residential area

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Castle Rock Road slide
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Side of a slideCleveland Corral slide
Left edge
http//vulcan.wr.usgs.gov/Projects/CalifLandslide/
Images
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Mill CreekJan. 1997
http//vulcan.wr.usgs.gov/Projects/CalifLandslide/
Images
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Mill Creekslide,blockedHwy 50
Hwy 50
http//vulcan.wr.usgs.gov/Projects/CalifLandslide/
Images
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Nationwide

• Slides problems mainly coincide with mountains
• Pacific coast
• Colorado
• Appalachians
• New Hampshire
• Alaska, Hawaii
• North America
• 50 deaths, 2,000,000,000 per year

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National slide hazard
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Coal slide tragedy

• In Aberfan, South Wales
• October 21, 1966
• Pile of debris from coal mine
• called a tip
• which had been weakened by water
• Slid 1 km
• Thru cottages, over a canal, then
• into Pantglas Junior High School
• Killed 144 people, 116 school kids

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SouthWalescoalslide
Murphy, 14-41
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Sinkhole, Floridatook 3 days to form, not really
a landslide
Keller, 7-21
Even flat land can have problems
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Hong Kong slide
Press, 1-20
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Rio de Janeiro
Keller, 7-13
Many landslide risk factors - steep, fractured
rock, rain, denudation
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Slides started by quakes

• 1971 San Fernando, lots of little ones
• 1994 Northridge, coastal slide
• Turkey, road closure
• Tadzhikistan slides, mud slide
• Montana, slide as a dam
• 1970 Peru quake had bad slide
• 1964 Alaska most dramatic example

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Before

• Sherman Glacier, Alaska

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After

• 1964 Alaska quake

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Dust from an aftershock
San Fernando quake
Iacopi, 28
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Obscure quake risk

• 1994 Northridge quake
• Lots of dust floated out over LA
• Valley Fever (not related to disco)
• Carried by spores in near-surface dust
• Incidence of Valley Fever doubled in months after
  quakes
• An extra 60 deaths
• Doubled death toll from Northridge

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Northridge slide
Davidson, 384
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Same Northridge plunge
Was a big house
Front cover - Vogel
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Slide from quake in Turkey
200 m
1966
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15 m high mudflow quake in Tadzhikistan, 1989
slopes weakened by rain
People now living on roof
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Landslide as a dam
100m high 28 buried 1959 quake
NOAA slides
Montana
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Turnagain Slide, Anchorage1964 Alaska

• Slide 3 km wide and 400 m deep
• A second slide dropped the business district 10
  feet
• Slide was previously recognized and mapped
• Area that slid has been rebuilt
• Best views in town

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1964 Turnagain Heights Landslideup close
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Slumping in downtown Anchorage from 1964 Alaska
earthquake
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Summary of soft ground

• Landslides
• Can result from natural or man-made problems
• Biggest slides are natural
• Soft soils have several problems
• Liquefaction, landslide, settling, river banks
• Indications of various problems are similar
• Yanev (an engineer) says to consult an engineer
• Tsunamis can hit some of the same areas

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Mitigation

• Land-use restrictions
• Dont live under slides
• Correct cut-and-fill techniques
• Dont denude hillsides
• Engineering
• Deflect or trap sliding material
• Keep hillside drained (more dry)
• Install retaining walls, anchors
• Monitor for sliding

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This map shows the scale of the landslide, which
slopped the contents of the reservoir over the
dam and killed more than 2000 people in Longarone
and the adjoining communitie
Upstream view of the landslide
The Vaiont landslide in the Dolomites (northern
Italy)
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A. Helmstetter, D. Sornette, J.-R. Grasso, J. V.
Andersen, S. Gluzman and V. Pisarenko, Slider-Bloc
k Friction Model for Landslides Implication for
Prediction of Mountain Collapse. J. Geophys.
Res., 109, B02409, doi10.1029/2002JB002160 (2004)
D. Sornette, A. Helmstetter, J.V. Andersen, S.
Gluzman, J.-R. Grasso and V.F. Pisarenko Towards
Landslide Predictions Two Case Studies, Physica
A 338, 605-632 (2004)
150
Key concepts
All slopes are subjected to damage and healing
processes accumulating over time. Some fail,
other take longer. It is just a matter of time
Most of our landscape is due to the
accumulation of landslides, triggered or not by
earthquakes. Like rupture of concrete in the
lab.
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European Alps pre-historical landslides
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30-yr probability of quakes in California
Parkfield
1906 repeat
1857 repeat
Yanev p. 39
1857-type is given 30 chance in 30 years
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Predicted shaking from Hayward fault event
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Combine earthquakes
From all known faults
and some model of unknown faults
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A probability map for SoCal
Number of times that 20 g will be exceeded per
century
SCEC web page
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World Hazard
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Philippines, 1990
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Europe,Middle East,and Africa
Turkey, 1999
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Americas
Mexico City, 1985
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Hazard and Risk

• Hazard probability that a given area will be
  affected by a given destructive process
• Risk Probability that a loss will occur

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Hazard and Risk, continued

• Hazard is what seismologists predict
• Includes earthquake probability
• Risk is what insurance companies, the government,
  etc. need to know.
• How do we close the gap?
• Risk hazard vulnerability value

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HAZUS Average Annualized EQ Losses

• Dr. Stuart Nishenko
• Senior Seismologist
• Building Sciences
• and Assessment
• Branch, FEMA
• WSSPC Conference
• Seattle, WA
• September 20, 2000

FEMA Federal Emergency Management Agency
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FEMA Hazus results

• Average Annual Earthquake Loss by state

Nishenko, 2002
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Average Annual Earthquake Loss per Capita for 35
Metropolitan Areas
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Cost-Benefit Analysis

• Benefit-cost ratio
• Calculate annual benefits
• Multiply by lifetime
• Calculate projected cost of
• special earthquake construction
• Take ratio to get benefit/cost ratio
• Would it be better to spend this money on new
  schools, hospitals, etc.

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Starquakes in neutron stars

• Flashes of soft g-rays repeaters
• Source of starquake fracture in the neutron star
  crust (1km thick)
• strain energy 1039 Joules gtgt 1019 Joules for
  largest earthquakes
• Star SGR1806-20 sun mass in 20km diameter,
  density 1014, rotation in 7.5s, magnetic field
  1015 Gauss.
• Crust made of solid lattice of heavy nuclei with
  free electron very heavy metal
• Stress loading magnetic forces

http//solomon.as.utexas.edu/duncan/magnetar.html
169
The Earths magnetic field, which deflects compass
needles
(measured at the N magnetic pole)
0.6 Gauss A
common iron magnet like those used to stick
papers on a refrigerator 100 Gauss
The strongest man-made fields achieved
so far in the laboratory
Sustained
(steady) 4 105 Gauss
The strongest man-made fields achieved so far
in the laboratory
Ephemeral (made using
explosives lasts only milliseconds)
107 Gauss The maximum field
observed on ordinary stars 106 Gauss
Typical magnetic field of radio pulsars
1012
Gauss (the ordinary, familiar kind of neutron
star (hundreds are known to astronomers)


Magnetars (soft gamma repeaters) 1014 -
1015 Gauss
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Case agt b application to starquakes
Comparison of numerical simulations and a
starquake sequence
(Sornette and Helmstetter, 2002)