Comparisons between L-band and C-band InSAR for large 2007-2008 earthquakes in Asia: Implications for future SAR missions and

earthquake studies

Zhenhong Li(1), John Elliott(2), Eric J. Fielding(3), Barry Parsons(2) and Richard Walters(2)

(1): COMET, University of Glasgow, Glasgow, UK(2): COMET, University of Oxford, Oxford, UK(3): Jet Propulsion Laboratory, Caltech, USA

06 Nov 2008

Large earthquakes in Asia in 2007 and 2008

Comparisons between C-band & L-band InSAR

Coherence

Phase gradients

Ionospheric effects

Conclusions

Contents

Large earthquakes in Asia (2007-2008)

Sep 2007 Sumatran

earthquakes(Mw 8.4 & 7.9)

May 2008Wenchuan(Mw 7.9)

March 2008Yutian

(Mw 7.2)

Jan 2008Gaize

(Mw 6.4 & 5.9)

The 2007 Sumatran earthquakes:

Coherence+

Temporary Resolution

(Konca et al, Nature, in press, 2008)

The 2007 Sumatran earthquake

The 2007 Sumatran earthquake

Mw 8.4: 12 Sep 2007

11:10:26 UTC

Mw 7.9: 12 Sep 2007

23:49:01 UTC

12 hours interval

4 tracks of ALOS PALSAR L-band interferograms

Note:

(1) All interferograms include signals

from both events!

(2) CGPS data available to distinguish

coseismic signals.

L-band Interferogram

The 2007 Sumatran earthquake

Google image

Note: NO coherence for C-band Data!!!

Implication: L-band has advantages over C-band in terms of coherence…

The 2008 Gaize earthquake:

Temporal Resolution of InSAR data

The 2008 Gaize earthquake

The 2008 Gaize earthquake

Mw 6.4: 09 Jan 2008

Mw 5.9: 16 Jan 2008

7 days interval

2 tracks of Envisat C-band interferograms+1 track of ALOS L-band image

(Feng et al., 2008, on preparation for CGJ)

Note:

All interferograms cover both events &

NO other data available to distinguish

coseismic signals

A BIG Challenge for modeling

The 2008 Gaize earthquake

Main fault: NW-dipping

Secondary fault:

Option 1: NW-dipping

Option 2:SE-dipping

Implication: Temporal resolution is a limitation …

(Feng et al., 2008, on preparation for CGJ)

The 2008 Yutian earthquake:

Phase gradients and wavelengths

The 2008 Yutian earthquake

The 2008 Yutian earthquakeFringes lost due to

large phase gradients

The 2008 Yutian earthquake

(L-band)(C-band)

Implication: Longer wavelength can be used to resolve deformation with greater phase gradients

The 2008 Wenchuan earthquake:

Ionospheric effects

&

Coherence

The 2008 Wenchuan earthquake

The 2008 Sichuan earthquake

Fault traces from SAR Range offset Maps

471

472

473

474

475

476 Track numbers: 471 - 476

Magnitude of c. 1 m within a distance of 200km

Magnitude of c. 0.5 m within a distance of 500km

Magnitude of c. 0.8 m within a distance of 400km

Implication: Ionospheric effects on L-band interferograms

cannot be neglected…

Coherence: ALOS vs Envisat

ALOS Envisat

Current SAR Satellites

SAR Satellitesrepeatcycle(days)

Bands

European ERS-1/ERS-2 1992-2001(+) 35 C

Canadian Radarsat-1 1995-present 24 C

European Envisat 2003-present 35 C

Japanese ALOS launched Jan. 2006 46 L

German TerraSAR-X launched July 2007 11 X

Italian COSMO-SkyMed 2 launched 2007 16/2 X

Canadian Radarsat-2 launched Dec. 2007 24 C

Future SAR Satellites (incomplete)

SAR Satellitesrepeatcycle(days)

Bands

European Sentinel-1 (2011) 12 CCanadian Radarsat Constellation Mission (RCM) (2012) 4 C

Indian RISAT (2009) 13 C

Chinese HJ-1-C (2008) -- SArgentinean SAOCOM-1 (2012) 16 L Brazilian + German Multi-Application

PurposeSAR (MapSAR) (2012)

37 L

Temporal resolution of current SAR systems is still a limitation for earthquake studies:

Combination of different data sets (e.g. X-, C- and L-bands)

More SAR satellites…

Conclusions

C-band L-band Notes

Coherence - +Tropospheric effects = = Identical

Ionospheric effects + - ~17 times greater at L-band than C-band

Phase gradients /Greater deformation - +

Measurement accuracy + - ~1.6 times (Sandwell et al., 2008)

Acknowledgements

JAXA ALOS AO project (ID: P0610001; PI: I. Dowman)ESA ALOS ADEN AO project (ID: 3577; PI: B. Parsons)

ESA AOE-621(PI: B. Parsons)ESA AOE-668 (PI: E. Fielding) DRAGON 2558 (PI: Q. Zeng)