Refining the Magnitude of Shallow Slip Deficit

XU, Xiaohua1; TONG, Xiaopeng2; SANDWELL, David T. 1; MILLINER, Christopher W.D3.; DOLAN, James F. 3; HOLLINGSWORTH, James3; LEPRINCE, Sebastien4; AYOUB, Francois4

1 University of California, San Diego

2 University of Washington, Seattle

3 University of Southern California

4 California Institute of Technology

Radar Interferometry

Fialko et al. 2001 (Hector Mine)

Radar Interferometry

Fialko et al. 2001 (Hector Mine)

Shallow Slip Deficit (SSD)

Simons & Filako, 2002 (Hector Mine)

Cumulative Strike Slip (m x km)

Shallow Slip Deficit: Large Strike Slip Eqs

Fialko et al. 2005, 2010

Shallow Slip Deficit

Scholz 1998

Shallow Slip Deficit

Possible Explanations for SSD

Shallow Creep/Aftershocks? ◦ No - Wei et al., [2010] Wei et al. [2011]

Triggered Slip? ◦ No - Sandwell et al.,[2000]

Off Fault Deformation? ◦ No - Shelf and Oskin [2010], Dolan et al. [2014]

Inelastic Deformation? ◦ Up to 15% - Kaneko and Fialko [2011]

Possible Explanations: Shallow Earthquakes

Scholz, 1998 (Parkfield) Wei et al., 2011 (El-Mayor)

Not Much Shallow Earthquakes

Possible Explanations: Shallow Creep

Jacobs et al. 2002

Fialko, 2004

Interseismic (Before Landers) Landers: 5.7 mm/year Hector: 2.9 mm/year

Savage et al., 2003

Possible Explanations: Triggered Slip

Sandwell et al. 2000

Hi-Pass Filtered Phase Gradient (East Direction) 1999 Hector Mine

Possible Explanations: Off-Fault Deformation

◦ Calico Cum-Slip 9.6 km Off-Fault Deformation ~ 23%

◦ Harper Lake Cum-Slip 3.6 km Off-Fault Deformation 31% ~ 46%

Shelf & Oskin, 2010

10%

Possible Explanations: Inelastic Deformation

Maximum 15% Deficit by Inelastic Deformation Extra 10% might be caused by using Elastic Model for

inversion.

Kaneko & Fialko, 2011

Possible Problems Cause By Large SSD

◦ Incorrect Slip Rate Estimation

◦ Ground Motion Prediction

◦ Paleo-Earthquake Magnitude

◦ Seismic Hazard Evaluation

Is the SSD Real? -Radar Decorrelation

Fialko, 2004

Synthetic Test

Xu et al. in prep

Synthetic Test

Xu et al. in prep

Data Preparation: Aerial Image Xcorr

Milliner et al. submitted

-National Aerial Photography Program/USGS

Data Preparation: Aerial Image Xcorr

Data Preparation: Aerial Image Xcorr

Along-Strike

Stri

ke S

lip

7m

70km 0

Data Preparation: Unwrapping

Xu et al. in prep

Non-Boxcar Filter New Unwrapping with SNAPHU Corr Mask and DEFOMAX Ramp estimated and removed during Inversion

Data Preparation: Unwrapping

Xu et al. in prep

Data Preparation: Additional GPS

Xu et al. in prep 2010 El Mayor Cucapah

In All: 82 for 1992 Landers 77 for 1999 Hector Mine 158 for 2010 El-Mayor Cucapah

Joint Inversion Results

GPS InSAR Aerial Image

Xu et al. in prep 1992 Landers

Joint Inversion Results

Xu et al. in prep 1992 Landers (Elastic Half Space)

New Shallow Slip Deficit

Xu et al. in prep

Discussions

Can the Shallow Slip Deficit be compensated now? ◦ Yes. Recall the Inelastic Deformation Study.

Is SSD uniform for these large strike-slip earthquakes. ◦ No, Varies from 3% - 19%

What affects SSD? ◦ Fault Maturity – Dolan & Haravitch [2014] ◦ Geological Structure

Conclusions

Our synthetic test showing missing data around fault may cause shallow slip deficit.

With acquiring more close-to-fault data, our inversion showed a large reduction in SSD.

The SSD now can be explained.

Mechanisms that can quantitatively explain why SSD varies with earthquakes is still in enigma. Assessing this deficit could give us a primary hint of the geological structure complexity along the fault.

Thank you

Questions? Comments?

Selected References

Simons, M., Fialko, Y., and Rivera, L. (2002). Coseismic deformation from the 1999 mw 7.1 hector mine, california, earthquake as inferred from insar and gps observations. Bulletin of the Seismological Society of America, 92(4):1390-1402.

Fialko, Y., Sandwell, D., Simons, M., and Rosen, P. (2005). Three-dimensional deformation caused by the bam, iran, earthquake and the origin of shallowslip decit. Nature, 435(7040):295-299.

Chen, C. W. and Zebker, H. A. (2001). Two-dimensional phase unwrapping with use of statistical models for cost functions in nonlinear optimization. JOSA A, 18(2):338-351.

Kaneko, Y. and Fialko, Y. (2011). Shallow slip decit due to large strike-slip earthquakes in dynamic rupture simulations with elasto-plastic o-fault response. Geophysical Journal International, 186(3):1389-1403

Okada, Y. (1992). Internal deformation due to shear and tensile faults in a half-space. Bulletin of the Seismological Society of America, 82(2):1018-1040.

Tong, X., Sandwell, D. T., and Fialko, Y. (2010). Coseismic slip model of the 2008 wenchuan earthquake derived from joint inversion of interferometric synthetic aperture radar, gps, and eld data. Journal of Geophysical Research: Solid Earth (1978{2012), 115(B4).

Backup Slides

Model Resolution

Fialko 2004

Tong et al. 2010

Need Far Field GPS to constrain the bottom

Resolution Test

Xu et al. in prep

Parkfield

Johnson et al. 2006

Data Preparation

Xu et al. in prep 1999 Hector Mine

Data Preparation

Xu et al. in prep

Data Preparation

Xu et al. in prep

Xu et al. in prep

Inversion Results

Xu et al. in prep

1999 Hector Mine

Inversion Results

Xu et al. in prep 2010 El Mayor-Cucapah

Weigh of On-fault Data

Xu et al. in prep 1999 Hector Mine

Smooth Factor

Xu et al. in prep 1999 Hector Mine

Discussion

Dolan & Haravitch. 2014