Systematic analysis of temporal changes in site response associated with strong ground motion in Jap...
This presentation is the property of its rightful owner.
Sponsored Links
1 / 12

Chunquan Wu Advisor: Prof. Zhigang Peng Collaborator: Prof. Dominic Assimaki (CEE) PowerPoint PPT Presentation


  • 134 Views
  • Uploaded on
  • Presentation posted in: General

Systematic analysis of temporal changes in site response associated with strong ground motion in Japan. Chunquan Wu Advisor: Prof. Zhigang Peng Collaborator: Prof. Dominic Assimaki (CEE) EAS Graduate Student Symposium 11/14/2008. Introduction.

Download Presentation

Chunquan Wu Advisor: Prof. Zhigang Peng Collaborator: Prof. Dominic Assimaki (CEE)

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Systematic analysis of temporal changes in site response associated with strong ground motion in Japan

Chunquan Wu

Advisor: Prof. Zhigang Peng

Collaborator: Prof. Dominic Assimaki (CEE)

EAS Graduate Student Symposium

11/14/2008


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Introduction

Site Effects: Ground motion can be significantly affected by the near-surface geological configuration.

From http://www-tamaris.cea.fr, http://eqseis.geosc.psu.edu, http://www.ce.washington.edu


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Nonlinear Site Effects

  • dynamic properties are strain-dependent

  • widely observed during major EQs

  • significant influence on ground shaking

  • important for realistic ground-motion predictions

  • the controlling parameters are still under discussion

Kokusho, Current Science, 2004


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Region and Data

  • KiK-net: 659 stations with a surface/downhole pair of strong-motion seismographs

  • ~70 station-event pairs with PGA above 300 gal

  • download records of ~17000 events

  • focus on the records of several large earthquakes


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Data Analysis Procedure

10s window

5s sliding

10s window

10s window

An M5.2 earthquake on Nov 04, 2004 recorded by NIGH06


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Temporal Changes of Spectral Ratio

MYGH04, 2003 Miyagi-Oki earthquake, PGA: 664.7 gal

MYGH03, 2003 Miyagi-Oki earthquake, PGA: 809.1 gal

TTRH02, 2000 Western Tottori earthquake, PGA: 927.2 gal

  • Surface-to-downhole horizontal spectral ratio

  • Peak spectral ratio decrease: 20-80%

  • Peak frequency drop: 15-85%

  • Recovery time scale: tens of seconds to several years


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Investigating the Role of PGA

  • 3 M>6 events within 1 hour after the Niigata MS.

  • 9 Nearby stations with PGA larger than 200 gal during the MS.


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Temporal Changes of Spectral Ratio

NIGH06, 2004 Niigata earthquake sequence

PGA: mainshock 409.8 gal, aftershock1 232.0 gal, aftershock2 202.8 gal, aftershock3 258.3 gal.


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Stacked Spectral Ratio Traces


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Drop & Recovery vs. PGA (peak ground acceleration)


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

The role of site condition: inversion (ongoing work)

  • Hybrid two-step optimization scheme

  • Successfully applied in Japan and California (Assimaki and Steidl, 2007; Assimaki et al., 2008a,b).

  • Currently applying to the Niigata mainshock and aftershock sequence.

MYGH04, 4 aftershocks of 2003 Miyagi-Oki earthquake

Assimaki, et al., BSSA, 2008a


Chunquan wu advisor prof zhigang peng collaborator prof dominic assimaki cee

Conclusions and Future Plan

  • Surface-to-downhole peak spectral ratio decreases 20-80%, peak frequency drops 15-85%

  • Recovery time scale: tens of seconds to several years

  • The co-seismic peak frequency drop and the post-seismic recovery time increase with the PGA at a given site.

  • The co-seismic peak frequency drop and the post-seismic recovery time can vary significantly at a certain PGA level under various site conditions.

  • The controlling mechanisms for the time scale of recovery is still not clear.

  • The ongoing work of seismogram inversion would shed more light on the role of soil properties & layer structures.


  • Login