The whole 2010-2011 New Zealand seismic sequence revealed by DInSAR and time-series data

Stefano SalviE. Trasatti, C. Tolomei,, J. Merryman, A. Antonioli, S. Atzori and M. Moro

Istituto Nazionale di Geofisica e Vulcanologia, Italy

P. Riccardi, P. Pasquali , A. Cantone

SARMAP sa, Switzerland

S. C. Bannister

GNS Science, New Zelaland

The following results have been produced in the framework of the SIGRIS project funded by ASI to demonstrate operational services for seismic risk management

(www.sigris.it)

• SIGRIS is a HW/SW infrastructure devoted to the generation of information products to support Civil Protection activities for Seismic Risk management.

• SIGRIS products are based on satellite imagery and integrate ground data where available.

• SIGRIS is operated by INGV (scientific institution).

• Main focus is on the use of COSMO-Skymed data.

The SIGRIS system

• Knowledge & Prevention, i.e. support to the Seismic Hazard assessment (demonstrated for the Italian territory)

• Warning & Crisis, i.e. support to the Emergency management (demonstrated worldwide)

The SIGRIS product families

SIGRIS demonstration for earthquake crises worldwide

• Central Pakistan , Mw=6.4, October 2008

• Chile, Mw=8.8, February 2010

• L’Aquila, Italy, Mw=6.3, April 2009

• Yushu, China, Mw=6.9, April 2010

• Canterbury, New Zealand, Mw=7.1, September 2010

• Christchurch, Mw=6.3, New Zealand, February 2011

• Tohoku, Japan, Mw=9.0, March 2011

The 2010-2011 New Zealand earthquake sequence

• September 4, 2010, the Darfield earthquake: Mw=7.1

• February 21, 2011, the Christchurch earthquake: Mw=6.3

• June 12, 2011, a further large earthquake: Mw=6.3

The Darfield earthquake

• Magnitude 7.1• September 4, 2010

Data sets for the Darfield EQ:

• ENVISAT • ALOS/Palsar

• EROS B (Optical)

• Seismological data

SIGRIS product: map of the fault scarps(EROS B data, 0.6 m resolution)

Map of the fault scarps

SIGRIS product: co-seismic deformation maps

ALOS

August 13September 28

Co-seismic deformation maps

ENVISAT

September 1October 6

Co-seismic deformation maps

ALOS

Dextral slip ~3.7 m

LOS

Co-seismic deformation maps

Azimuth displacement from ALOS dataIntensity cross-correlation ; 1 km x 1 km windows ; 200 m x 200 m posting

Displacement corrected for ionospheric

errors [Raucoules

and De Michele, GRSL 2010] :

Co-seismic deformation maps

Slant-range displacement from offset-trackingMean accuracies (coherence = 0.5) = 1/60th of the resolution cell (20 cm)

SIGRIS product: seismic source models (incremental)

Non- linear inversion

Geometries constrained also by relocated seismicity

Seismic source models (incremental)

Non- linear inversion

Geometries constrained also by relocated seismicity

View from the N

View from the SW

Seismic source models Linear inversion

Geodetic Mo=4.7 1019 Nm

Seismic Mo=3.5 1019 Nm (USGS)

Variable patch size approachAtzori and Antonioli, 2011, Optimal fault resolution in geodetic inversion of coseismic data, Geoph. J. Int.

View from the NE

Red: modelGreen: ALOS data

SIGRIS planned COSMO post-seismic acquisitions after the Darfield earthquake

16-day repeat pass

At least 1 year ascending and descending coverage

The Christchurch earthquake

• Magnitude 6.3• February 21, 2011

Data sets for the Christchurch EQ:

• COSMO-SkyMed (data acquisition started October 2010)• ALOS/Palsar

• Seismological data

SIGRIS product: co-seismic deformation maps

ALOS COSMO COSMO

SIGRIS product: seismic source models (incremental)

Linear inversion

Geodetic Moment2.4 * 1018 Nm

Seismic Moment 1.9 * 1018 Nm (USGS)

The Christchurch earthquake source

Christchurch

+50 cm

- 10 cm

Further products: stress transfer analysisNo prior knowledge on other active faults in the Canterbury plain (all buried faults)

A posteriori analysis:CFF projected on the February 21 fault plane: all positive with maximum value 1.5 bar

Further products: post-seismic analysis

COSMO-SkyMed acquisitions between the Darfield and Christchurch earthquakes (~5 months):

•12 images from the ascending orbit•14 images from the descending orbit

We used the SBAS technique (SarScape version).

ALOS post-seismic interferogram (+8, 45)

GE

GW

GWGE

COSMO ascending post-seismic interferogram (+41, 170)

GE

GW

GE

COSMO descending post-seismic interferogram (+34, 170)

GE

GW

GE

‐50

‐40

‐30

‐20

‐10

0

0 20 40 60 80 100 120 140 160

Displacem

ent, mm

Days since earthquake

COSMO ascending time series

Mean Up velocity from COSMO (+40,170)

Analysis of the post-seismic time series by FEM

CONCLUSIONS

• A complex sequence of fault ruptures• Possible stress triggering for the Christchurch earthquake• Important role of fluids• Complex mix of post-seismic signals: afterslip, pore pressure

readjustment, possibly dilatancy recovery• Dense InSAR time series are the only way to fully analyse

these phenomena