Integrating GPS and InSAR to Measure Moment Rates along the San Andreas Fault System

David T. Sandwell, Meng Wei, Xiaopeng Tong, Bridget Smith-Konter

IGARSS, July 28, 2011

IntegratingGPS and InSAR

• strain rate and seismic moment rate measure earthquake potential

• strain rate not well resolved by GPS, need InSAR

• L-band correlation >> C-band (Rosen et al., 1996; Wei and Sandwell, 2010)

• remove-filter-stack-restore to integrate GPS and InSAR

• SAF results

• need MORE L-band data, ALOS-2 and DESDynI

[data from JAXA and provided through the ASF; funding - NASA, Geodetic Imaging]

M = µΛ(∆ − δ)ς Τ&ΜΛ

= µς (∆ − δ)

strain rate

&ε =

V

p d=

velocity

locking depth

&M

L= µς ∆

moment rate

IntegratingGPS and InSAR

• strain rate and seismic moment rate measure earthquake potential

• strain rate not well resolved by GPS, need InSAR

• L-band correlation >> C-band (Rosen et al., 1996; Wei and Sandwell, 2010)

• remove-filter-stack-restore to integrate GPS and InSAR

• SAF results

• need MORE L-band data, ALOS-2 and DESDynI

[data from JAXA and provided through the ASF; funding - NASA, Geodetic Imaging]

strain rates from 16 groups

InSAR can resolve near-fault velocity

need ~2 mm/yr precision

IntegratingGPS and InSAR

• strain rate and seismic moment rate measure earthquake potential

• strain rate not well resolved by GPS, need InSAR

• L-band correlation >> C-band (Rosen et al., 1996; Wei and Sandwell, 2010)

• remove-filter-stack-restore to integrate GPS and InSAR

• SAF results

• need MORE L-band data, ALOS-2 and DESDynI

[data from JAXA and provided through the ASF; funding - NASA, Geodetic Imaging]

interseismic vector velocity model

east north up

[Smith-Konter and Sandwell, 2009]

locked zone

InterseismicLOSVelocity

high-passfilteredλ < 40 km

ALOShas the best sensitivityto interseismic motion.

ERSascending

ERSdescending

ALOSascending

ALOSdescending

[Wei et al., 2010]

locked zone

InterseismicLOSVelocity

high-passfilteredλ < 40 km

Ascending ALOS has 8-20 repeats

ERS/Envisatascending

ERS/Envisatdescending

ALOSascending

ALOSdescending

poorcorrelation

poorcorrelation

too fewrepeats

[Wei et al., 2010]

remove/restore this LOS model

align and stack with GMTSARunwrap phase with snaphu[Chen and Zebker, 2002]

IntegratingGPS and InSAR

• strain rate and seismic moment rate measure earthquake potential

• strain rate not well resolved by GPS, need InSAR

• L-band correlation >> C-band (Rosen et al., 1996; Wei and Sandwell, 2010)

• remove-filter-stack-restore to integrate GPS and InSAR

• SAF results

• need MORE L-band data, ALOS-2 and DESDynI

[data from JAXA and provided through the ASF; funding - NASA, Geodetic Imaging]

mean LOS red 10 mm/yrblue -10mm/yr

std edit > 6 mm/yr

southern SAF red 10 mm/yrblue -10mm/yr

southern SAF red 10 mm/yrblue -10mm/yr

San Jacinto stepover red 10 mm/yrblue -10mm/yr

San Jacinto stepover red 10 mm/yrblue -10mm/yr

LA Basin red 10 mm/yrblue -10mm/yr

LA Basin red 10 mm/yrblue -10mm/yr

Parkfield SAF red 10 mm/yrblue -10mm/yr

Parkfield SAF red 10 mm/yrblue -10mm/yr

Creeping SAF red 10 mm/yrblue -10mm/yr

Creeping SAF red 10 mm/yrblue -10mm/yr

Creeping SAF

LOS error~4 mm/yr

frame processing

frame processing

frame processing

frame processing

frame processing

frame processing

frame processing

frame processing

frame processing

frame processing

frame processing

Conclusions

•strain rate and seismic moment rate measure earthquake potential

•combining GPS and InSAR provides full spatial resolution

•C-band InSAR does not have adequate coherence for interseismic studies

•ALOS provides 10-20, long time span (2.4 yr), interferograms along ascending orbits resulting in 4 mm/yr noise. ~ 800 SAR images were used for this analysis.

•Need more repeats as well as descending coverage from ALOS-2 and DESDynI to achieve 2 mm/yr. Need > 60 repeats for each of 58 frames or ~3400 scenes.[data from JAXA and provided through the ASF; funding - NASA, Geodetic Imaging]

interseismic model

velocity

strain rate

momentrate

v(x) =ςπ

ταν−1 ξ∆

&ε x( ) =V

p D

1

1+x

Dæèç

öø÷

2

&M

L= µς ∆

= velocity depth

= velocity X depth