Solid Earth Seismology
Theory, Practice, and Application to the Earth's Interior
GEOL 595 SP/L
Text Book: Introduction to Seismology
By Peter M. Shearer
What is Seismology ?
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From the Greek root word: “seismos” to shake
Seismic Waves: elastic wave energy
that propagates in solid or fluid materials.
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Seismology: the study of earthquakes and
the elastic waves generated by the rupture.
What is Seismology ?

Seismic Waves: elastic wave energy
that propagates in solid or fluid materials.
- energy creation
(earthquakes, nukes, bombs, eruptions, sonic booms)
- energy transmission
(propagation, absorption, scattering, reflection, diffraction)
- energy recording
(seismometry, computer storage, data transmission, etc)
- societal
(e.g., forecasting earthquakes, tsunami, seismic)
What is Seismology ?
Seismology bridges:
Geology +
Geophysics + Earth Science
Seismic imaging at depth can verify whether geological
observations (e.g. faults, plate boundaries,ancient sutures, granitic outcrops)
on the surface continue to deeper depths in the crust or mantle.
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Earthquake aftershocks can help us map faults and plate boundaries
at depth in the crust and mantle.
Measurements of seismic anisotropy can indicate whether
mineralogical alignment occurs during plate movement or shear.
Volcano seismology measure earthquake patterns that may
indicate magma rising through a volcano chamber
Mount St Helen's
movie
* Erupted 1980, Washington State
* Local earthquakes felt 2 months before
* Evacuations saved 1000's of people
* 57 people died including Inn keeper
Harry Truman, a photographer,
a geologist, and many animals.
Earthquakes can tell us about
Magma Flow beneath Volcanoes
- An eruption event at Mt St Helen's in September, 2005
- Can be seen in the earthquake record by deep events of magma flow
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
The map on the right shows historic
earthquake activity near the epicenter
(star) from 1990 to present.
As shown on the cross section,
earthquakes are shallow (orange
dots) at the Japan Trench and
increase to 300 km depth (blue dots)
towards the west as the Pacific Plate
dives deeper beneath Japan.
Seismicity Cross Section across the subduction zone
showing the relationship between color and
earthquake depth.
Images courtesy of the US Geological Survey
Northridge Earthquake, 1994
San Fernando, 1971
Northridge, 1994
Seismic image of a blind thrust fault at depth
Seismology and Society
Study of Seismology, seismic waves, and earthquakes
Also aid in hazard analysis for communities in earthquake country.
- Earthquake risk
- Earthquake Engineering
- Tsunami hazard analysis
Northridge Earthquake, 1994
- January 17, 1994, 4:30 am
- Magnitude = 6.9
- Blind thrust fault
- Difficult to find or predict
- Duration 10-20 seconds
CSUN Parking Structure
Many Active Faults in Southern California
And more offshore!
 How close do you live to a fault ?
 Los Angelino's need to know and need your help to prepare!
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L.A. mayor's proposals for concrete, wood
quake retrofits
Los Angeles Times
Monday, Jan 26, 2015
The mayor's proposals for mandatory retrofits target two of the riskiest types of
structures built in Los Angeles before 1980: brittle concrete buildings and multistory wooden buildings supported by weak columns on the ground floor.
lRelated L.A. mayor calls for mandatory earthquake retrofitting for thousands of
buildings
L.A. mayor's proposals for concrete, wood quake retrofit
The mayor's proposals for mandatory retrofits target two of the riskiest types of structures
built in Los Angeles before 1980: brittle concrete buildings and multi-story wooden buildings
supported by weak columns on the ground floor.
lRelated L.A. mayor calls for mandatory earthquake retrofitting for thousands of buildings
Concrete Buildings:
Retrofit deadline: 30 years
Cost of retrofit: Varies. Could be more than $1 million for a 10-story building
Affected buildings: About 1,500 need further study to determine if retrofit is needed
Vulnerabilities: Many don't have enough steel reinforVulnerabilities: Many don't have enough
steel reinforcement to hold columns in place during shaking. The collapse of two concrete
office towers killed 133 people in a 2011 quake in New Zealand.
Wooden Buildings:
Cost of retrofit: About $60,000 to $130,000 for a modest-sized apartment building
Affected buildings: About 17,000 need further study to determine if retrofit is needed
Vulnerabilities: These types of buildings have collapsed during both the 1989 Loma Prieta
and 1994 Northridge earthquakes. Sixteen people died when the Northridge Meadows
apartment complex pancaked.
ALBACORE Project
Caltech, UCLA, CSUN
Offshore faults, seismicity, tsunami risk analysis, bathymetry
 Body wave, surface wave tomography, ambient noise, SKS splitting
 Recorded passing of Honshu earthquake tsunami on seafloor
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Northridge Earthquake, 1994
* CSUN Parking Structure (near G3 and G4 parking lot today)
* Built in 1991, three years before the earthquake.
Northridge Earthquake, 1994
Earthquake damage to freeways, buildings, cars, gas li
Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
This tsunami
propagation
forecast model
shows the forecast
maximum tsunami
wave height (in
cm).
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Interference of
water waves with
seafloor
bathymetry affects
the wave
trajectory, and
reflections.
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Travel up a
continental shelf
raises wave height
quickly.
.
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Magnitude 9.0 NEAR THE EAST COAST OF HONSHU, JAPAN
Friday, March 11, 2011 at 05:46:23 UTC
Projected travel times
for the arrival of the
tsunami waves across
the Pacific.
Nearby the earthquake
there are only minutes
to evacuate. However,
in many other regions
there is advance
warning.
A tsunami map shows projected
travel times for the Pacific
Ocean. This map indicates
forecasted times only, not that a
wave traveling those distances
has actually been observed..
NOAA
Magnitude 7.3 Earthquake near El Salvador
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Earthquake Mg 7.3 (Aug 26, 2012)
Offshore Elsalvador (9:30 pm California time)
Tsunami warning was put into effect for Costa Rica, Nicaragua,
El Salvador, Honduras, Guatemala, Panama and Mexico.
What is Seismology ?
The underlying physics is simple:
Force,
F = ma
Velocity,
V=d/t
But assumptions can quickly become complex when considering
realistic sources, Earth structure that changes with depth and pressure,
and receiver instrumentation.
Requires more sophisticated math and computation.
Earthquake Source Theory
Quantification of the earthquake rupture process
Early Detectors of Ground Movement
Zhang Heng was a celebrated astronomer of ancient China. An inventor of the
seismoscope and armillary sphere, he made great contributions to the development of
astronomy in ancient China.
132 AD, Eastern Han Dynasty
Seismology and Plate Tectonics
Earthquakes generally occur at plate boundaries.
 Thus plate tectonics is intimately linked with earthquakes and seismology
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Seismology and Plate Tectonics
Most of the largest earthquakes occur at collisional plate boundaries.
Planetary Seismology ?
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What kind of living would a seismologist make on another planet ?
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What is the plausibility of earthquakes on other planets, on the moon ?
- Is there active plate tectonics on other planets ?
Seismic waves inside the Earth
How does earthquake energy travel through the Earth's interior ?
Movie: Wysession
Seismic Tomography: from Seismic rays in the Earth
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Many seismic stations placed across a region of interest
Create Images of “velocity” or seismic structure
US Array
www.iris.edu
Earth's Interior Structure
Seismology is the chief method of determining the interior
Structure of the Earth.
Indirect methods of studying the Earth's Interior
Can we just go
to the center of the Earth ?
• Deep interior of the Earth must be studied indirectly
– Direct access only to crustal rocks and
small upper mantle fragments brought
up by volcanic eruptions or slapped
onto continents by subducting
oceanic plates
– Deepest drill hole reached about
but did not reach the mantle
• Geophysics is the branch of geology
that studies the interior of the Earth
12 km,
SE Germany – 10 km drill hole
Indirect Study of the Earth's Interior - Geophysics
- Seismic Waves
- Gravity
- Heat Flow
- Magnetic Field
The Mantle Lithosphere
• Crust and upper mantle together form the
lithosphere, the brittle outer shell of the
Earth that makes up the tectonic plates
– Lithosphere averages 70 km thick
beneath oceans and 125-250 km
thick beneath continents
The Asthenosphere
• Beneath the lithosphere, seismic wave speeds abruptly decrease in
a plastic (ductile) low-velocity zone called the asthenosphere
• Are low seismic velocities caused by partial melt, water, density?
Subduction Zones in North America
Subducting Farallon slab is
imaged through seismic
tomography extending to at
least 2000 km depth
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Farallon reaches this depth
somewhere beyond the east
coast of North America
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Grand et al., 2001.
Earth's resources
Oil exploration
Active source
Reflection seismology
Gasoline contamination
Environmental compliance
The Earth's Natural Resources
• Energy
• Water
• Raw Materials
• Energy
1. Oil
2. Natural Gas
3. Coal
4. Solar
5. Wind
6. Dams
Fossil Fuels
Oil Resources
New technologies used aboard offshore platforms in the Gulf of Mexico can
recover oil and gas from rock reservoirs below very deep waters. [Larry Lee Photography/CORBIS.]
Oil Resources: New Find in Gulf of Mexico!
(Will this solve all our problems ?)
New find in GOM
(Jack No. 2 test well)
• up to 3-15 billion barrels of oil
• US consumption 20 million barrels/day
(that's ~7.3 billion barrels/year)
• 5 months - 2 years
• reservoir is 8 km under sea level
Oil Consumption in U.S.
• U.S. Oil consumption
in 2007 was
20.68 million barrels per
day!
• This is 3 times as
much as China,
8 times Germany, 10
times France,
12 times England,
12 times Iran,
28 times Venezuala,
usage of oil.
• We are the biggest oil
consumer in the world.
Oil Peaks – 1960's
In the 1850's oil mainly used for
kerosene lamps – remaining
was burned or disgarded.
Current oil production rates peaked
in 1960's but U.S. consumption rates
increase dramatically above this.
Don't panic!
-Try to conserve energy
-Seek alternative energy sources
Petroleum Reserves
• As petroleum prices rise, alternate
petroleum sources, such as heavy
crude, oil shale and oil sand, will be
increasingly exploited
– Heavy crude is dense, viscous petroleum
– Oil shale is black or brown shale with high solid
organic matter content from which oil can be
extracted by distillation
– Oil sands (or tar sands) are asphalt-cemented sand
or sandstone deposits
Seismologists must image anticlines, petroleum traps,
liquid reservoirs, partial melt along grain boundaries.
Petroleum Exploration and Production
Depiction of a three-dimensional seismic survey collected from airguns
dragged behind a ship. Sounds waves reflect off the seafloor and deeper
sediment layers. The colors show the layers of sediments beneath the seafloor,
some trapping oil and natural gas. [ (b) Courtesy of Satoil, Veritas, and BP.]
Exploration Geophysics
CSUN students (Robin Sehler) in the field in south Africa
 Learn geophysical exploration techniques\
 Map and locate palladium veins in crustal rocks
 GPS, active source seismology, GPR, gravity, Magneto tellurics

( Robin Sehler, Carol Zamora, Gabrielle Zamora, Cristo Ramirez, Melissa Nunley
Jasmyn Nolasco, Brittany Huerta, Christian Mirreles)
The Seismogram
A seismogram is made up of a series of signals only one of which
is the earthquake.
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Earthquake source
 Scalar
 Explosion
• Rupture along a plane (e.g. shear or vertical slip)
Medium wave travels through
Receiver characteristics
Earthquake Sources and Seismometer Receivers
Stein and Wysession (figure 1.1-1)
Seismology: What is Known a
What we know for sure!
- Vp speed
- Average radial velocity of Earth
- Earthquake locations
- EQ radiation patterns
(fraction of a percent)
Known very well fo 50 years!
Mapped daily by GSN
“
What we are still studying:
- Physics of earthquake rupture
largely unknown.
- Damping by inner core
Only approximate
– Anisotropy in the inner core ? Still trying to find the J phase!
Earthquake Sources and Seismometer Receivers
To understand the seismogram observed at a seismometer
We must understand
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Earthquake sources
How the medium behaves, deforms, relaxes
The response characterists of the seismometer instrument
How seismic waves are generated and travel
Northridge Earthquake, 1994
- January 17, 1994, 4:30 am
- Magnitude = 6.9
- Blind thrust fault
- Difficult to find or predict
- Duration 10-20 seconds
CSUN Parking Structure
Northridge Earthquake, 1994
* CSUN Parking Structure (near G3 and G4 parking lot today)
* Built in 1991, three years before the earthquake.
Northridge Earthquake, 1994
Damage to freeways, buildings, cars, gas lines.
Historic Earthquakes
1994 Northridge
- 1.8 miles from CSUN
- Shaking 40 seconds
- Damaged all 53 CSUN buildings
- Damaged 300 other schools
- Lower story buildings collapsed
- 4 interstate hwy's closed for months
(Golden State, Santa Monica fwys)
- 15000 people live in tents for days
- 10000 without water, elect, gas
- Arid climate did not cause liquifaction of soils – s
(compared to 1964 Alaska and 1989 Loma Priet
- Landslides in Santa Susana, Santa Monica, San
blocked roads and traffic, damaged water lines
- Sylmar – Olive View Hospital – rebuilt from 1971
Earthquakes
1989, Loma Prieta earthquake, Mw = 7.2
Historic Earthquakes
1906 San Francisco
- 280 miles of displacement
- Shaking ~1 minute
- Damaged water mains, fires spread and caused many death
Historic
Earthquakes
1989 Loma Prieta, Mw = 7.2
- Shaking for 15 seconds
- Death toll 63
Historic
Earthquakes
1964 southern Alaska (Mw = 9.2)
- Shaking for 3 minutes
- Rupture 350,000 square miles
- Death toll from quake 15 (remote area)
- Tsunami, landslides 100 more
Historic Earthquakes
2002 inland Alaska – Denali Fault
- Propagated east 7000 miles/hr
- Offset streams, glaciers, landslides
- Trans-Alaska Oil Pipeline no
serious damaged - pre-engineered
Historic Earthquakes
2004 Sumatra – Andaman E.Q.
- Mw = 9.3
- Second largest recorded on Earth
- Major damage in Sumatra
- Tsunami damage spread far to
Indonesia, Thailand, Sri Lanka,
India, East Africa
- Death toll 220,000 from force
of tsunami wave
- Tsunami movie
Harnessing Nuclear Energy
Japan’s Kashiwazaki-Kariwa facility is the world’s largest nuclear power plant, with seven
reactors and a total generating capacity exceeding 8200 megawatts. It was damaged by a powerfu
earthquake (magnitude 6.8) that struck the region on July 16, 2007. The plant was shut down and
required extensive repairs. [STR/AFP/Getty Images.]
Petroleum Recovery
• Oil fields are regions underlain by
one or more oil pools
– Largest in U.S. are in Texas and Alaska
• Oil and natural gas are removed
through wells drilled down into an
trap within a reservoir rock
• Negative environmental effects
resulting from oil recovery and
transport include oil spills, brine
contamination of surface water,
ground subsidence
oil
and
Exploration Geophysics
CSUN students (Robin Sehler) in the field in south Africa
 Learn geophysical exploration techniques\
 Map and locate palladium veins in crustal rocks
 GPS, active source seismology, GPR, gravity, Magneto tellurics

( Robin Sehler, Carol Zamora, Gabrielle Zamora, Cristo Ramirez, Melissa Nunley
Jasmyn Nolasco, Brittany Huerta, Christian Mirreles)
Exploration Geophysics: Metals and Ores
• Metal ores - naturally occurring
materials that can be profitably mined
• Whether or not a mineral deposit is an
ore depends on chemical composition,
the percent extractable metal, and
current market value of the metal
• Metallic ore deposits originate from
crystal settling in igneous intrusions,
hydrothermal fluids cooling in pores
and factures, chemical precipitation in
water, or sedimentation in
rivers
(placers)