Estimation of the Fault Constitutive Parameter As and Stress Accumulation Rate from Seismicity Respo

1
Estimation of the Fault Constitutive Parameter As
and Stress Accumulation Rate from Seismicity
Response to a Large Earthquake

• Kenji MAEDA
• Meteorological Research Institute, JMA

2
Objectives

• Estimate the fault constitutive parameter As from
  the seismicity response to a large earthquake.
• Estimate the stress accumulation rate from the
  seismicity response to a large earthquake.
• Estimate the stress change from seismicity data.

3
Slip Speed vs. Time to Instability
Dieterich(1994)
4
Seismicity rate after the stress step
Dieterich(1994)
5
Seismicity rate after the stress step
Dieterich(1994)
6
Seismicity rate after the stress step
Dieterich(1994)
7
(No Transcript)
8
Stress Step Seismicity Rate Change
9
When we select the target area to apply the
method, we pay attention to

• The fault model of a large earthquake is well
  determined.
• The seismicity rate change caused by a stress
  step is clearly recognized.
• The area is far enough from a large earthquake
  not to be effected by a slip inhomogeneity of the
  earthquake.
• The rate change tend to follow Omoris formula.

10
dCFF by the 2003 Tokachi-oki Eq.
11
Seismicity in Hokkaido
12
Space-Time Distribution of Eqs.
13
Investigated Regions
14
Region A (No decluster)
15
Declustering Algorithm
16
Region A (Decluster 1km,1day)
17
Region A (Decluster 2km,2day)
18
Region C (No Decluster)
19
Region C (Decluster 3km,7day)
20
Fitness of (Modi-)Omori Form.
21
Parameters of (Modi-)Omori Form.
22
Obtaining Stress Change from Seismicity Rate
Change
Dieterich(2000)
23
Declustered Seismicity Change and Estimated Stress
24
Horizontal Movement (1/1/032/28/05)
GPS data from GSI
25
Baseline Length and Estimated Stress
26
Estimated Values
27
Estimated Values
28
Non-declustered Seismicity Change and Estimated
Stress
29
Summary

• The fault constitutive parameter As is estimated
  from the declustered seismicity that is activated
  by a large earthquake.
• The reference stress accumulation rate is also
  estimated by assuming no large stress change
  followed the mainshock.
• The time variation of stress is estimated from
  the seismicity rate change by using estimated As
  and stress accumulation rate .