YES Media : elasticity or visco ... rate- and state

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Earthquakesmechanism and prediction

• Koshun Yamaoka
• Earthquake Research Institute,
• The University of Tokyo
• yamaoka_at_eri.u-tokyo.ac.jp

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Earthquakes and Their disaster reductionSummary
of the course

• Earthquakes, their mechanism and prediction by
  Koshun Yamaoka.
• Innovative technology for monitoring the surface
  of the earth from the space, by Makoto Murakami.
• Strong ground motion and earthquake disaster,
  Analysis and Prediction, by Hiroshi Kawase.
• Seismic imaging of the earths deep interor and
  the dynamics of the subducting oceanic plate, by
  Hitoshi Kawakatsu.
• Long-term earthquake forecasts and earthquaek
  preparedness, by Kunihiko Shimazaki.

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ERI and history of earthquake research in Japan

• 1880 First Seismological society in the world is
  established in Japan
• 1891 Nobi earthquake (M8.0)
• 1892 Committee for Earthquake research and
  disaster reduction is established by the
  government
• 1923 Great Kanto Earthquake (M7.9)
• 1925 ERI is established
• 1962 Blue print of earthquake prediction
  research
• 1965 National program for earthquake prediction
  started
• 1995 Kobe earthquake (M7.3)
• 1998 New national project for earthquake
  prediction started

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Plate tectonics and earthquakes
Large deformation and Earthquakes
Inland earthquakes
Ridge and transform fault
Collision
Subduction
Interplate Earthquakes
Most of earthquakes concentrate around subduction
and collision boundaries
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Global tectonic map
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Global activity of earthquakes
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Earthquakes in the circum-pacific region (USGS)
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Seismic activity around Japan(USGS)
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Plate configuration around Japan
North-American plate
Eurasian Plate
Pacific Plate
Philippine Sea Plate
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Seismicity map in the Southeast Asia (NEID)
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Plate tectonics in Asia
Eurasian plate
Philippine Sea plate
Pacific plante
Indo-Australia plate
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Topography of Central Asia
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Seismicity of Central Asia(USGS)
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Strength of earthquakeIntensity and Magnitude
Intensity
Scale showing severity of surface shaking
Scale showing energy of underground phenomena
Magnitude
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Faults that appeared at the time of 1995 Kobe
earthquake (M7.3). Nojima Fault (Awaji, Japan)
Origin of earthquake or result of earthquake ?
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Generation of Earthquake
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Generation of earthquakePropagation of slippage
Epicenter
Ground surface
Faultsurface
Magnitude corresponds to the Size of fault
Faulting
Hypocenter (Start point of rupture)
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Magnitude and Fault size(M1-M4)
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Magnitude and Fault size (M3-M6)
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Magnitude and Fault size (M5-M8)
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Actual slip of 1923 Kanto earthquake(M7.9)
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2004 Off Sumatra Earthquake (M9.3)
200km x 1000km
1000km
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Mainshock and Aftershocks at 2004 Sumatra
earthquake (USGS)
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Intensity depends on distance to the hypocenter
and magnitude
M6
M7
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Seismic Intensity (Shindo) by ten grades in
Japan
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How do we predict earthquakes?

• Based on
• Unusual behavior of animals?
• Unusual cloud, which is called earthquake cloud ?
• Catfish ?

NO
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Three requirements in earthquake prediction

• WHEN (Time)
• WHERE (Place)
• HOW BIG (Magnitude)

Earthquake prediction is to know these components
with practical accuracy before an earthquake.
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Classification of earthquake prediction in terms
of time accuracy.

• Long-term prediction
• Statistical prediction using time history of
  earhtquake occurrence.
• Mid-term prediction
• Computer simulation based on physical model using
  monitoring data.
• Short-term prediction
• Prediction using precursory phenomena of
  earthquakes.

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Present State of earthquake prediction (in Japan)
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Why can we predict place and magnitude ?

• Based on Asperity model.
• Established recently for inter-plate earthquakes.
• Segmentation of active faults.

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Plate tectonics and earthquakes
Large deformation and Earthquakes
Inland earthquakes
Ridge and transform fault
Collision
Subduction
Interplate Earthquakes (Sunduction-type
earthquake)
Most of earthquakes concentrate around subduction
and collision boundaries
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Interplate earthquakes
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Asperity model
Rate-and-state friction law are applied on the
plate boundary
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Asperity Model
Asperity does not change during
earthquakes. One or more asperities rupture
simultaneously, results in variation in
earthquake magnitudes.
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Simple experiment on slow-slip and stick-slip
Sand paper
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(No Transcript)
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Stable sliding and Stick Slip
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Long-term earthquake prediction

• Stochastic estimate of earthquake occurrence
  based on earthquake history
• Time predictable model
• The probability of the occurrence of Tonankai
  earthquake in the next 30 years is 50.

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Historical earthquakes
Historical earthquakes repeatedly occurred in the
southern part of Japan with various combinations
of three asperity patches.
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Estimation of probability
For a specific fault
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Mid-term earthquake prediction

• Computer simulation based on physical model using
  monitoring data.
• Mathematical formulation is necessary
• Do we have Differential Equation for Earthquake
  prediction ?
• YES
• Media elasticity or visco-elasticity
• Faulting rate- and state- dependent friction law
• Stable sliding and Stick Slip are produced.

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Rate and state dependent friction law
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Seismic or Aseismic controlled by (a-b) and L
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Methodology of modern earthquake
prediction-learning from Sinking of Japan
Research on Mechanism
Create a Physical model
Monitoring of Activity
Predictive simulation with computers
Prediction for future events
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Mid-term earthquake prediction
Is earthquake impending?
Monitoring strain Seismic activity slip on
earthquake fault ...
Computer simulation for stress state on
earthquake fault.
Physical model based on research on earthquake
process throughout earthquake cycle
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Monitoring with GPS network
Traditional leveling survey
GPS observation stations
More than 1300 stations
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We can monitor the deformation in the period when
earthquake do not occur.
Geographical Survey Institute
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Computer Simulation on Earthquake Cycle
Simulation results
Tokai EQ
Tonankai EQ
Nankai EQ
Houei Ansei Showa
1707
1854
1854
1946
1944
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Short-term earthquake prediction

• Predict the occurrence of earthquakes by
  detecting phenomena which show the state
  immediately before earthquake.
• Only Pre-slip has a theoretical and experimental
  basis for precursors, but yet be detected.
• Short-term prediction requires intensive
  observation, because pre-slip can be very small.
• Search for precursore where big earthquakes are
  found to be impending by mid-term prediction.

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What is pre-slip
EARTHQUAKE!
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Simulation on earthquake occurrence
Velocity strengthening
Velocity weakening
Model
Simulation on Slip velocity
Kato(2004) JGR
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Summary of the lecture

• An earthquake is a slip along fault surface.
• Fault surface of (at least) inter-plate boundary
  composed of asperities that are surrounded by
  region of aseismic slip (or steady sliding)
• Long-term earthquake prediction, which is based
  on the statistics using time history of
  earthquake occurrence, can be made, and issued in
  Japan.
• Mid-term earthquake prediction, which is based on
  computer simulation with physical model using
  monitoring data, are now developing.
• Short-term earthquake prediction, which is based
  on precursory phenomena such as pre-slip, is
  still difficult.