Mega‐earthquake vs. small size seismic events: tradeoff and limits of Remote Sensing in thetradeoff and limits of Remote Sensing in the application to source parameters retrieval

Stramondo S. 1, Bignami C.1, Cannelli V.1, Melini D.1, Moro M.1, P l i M 1 S S 2 S li M 3 V li P 1Polcari M.1, Samsonov S.2, Saroli M.3, Vannoli P.1

1Istituto Nazionale di Geofisica e Vulcanologia, Rome, Italy (salvatore.stramondo@ingv.it)2Canada Centre for Remote Sensing, Ottawa, Canada 3University of Cassino and Southern Lazio, Dept. of Civil and Mechanical Engineering, Cassino, Italy 

OUTLINE‐Differential SAR Interferometry (DInSAR): how it works

‐ Satellite missions: state of art

‐Trade‐off Magnitude‐Depth: which limitations for DInSAR

‐ Small‐scale earthquakes: case studies

“Picture” of time vs space evolution of a seismic swarm‐ Picture  of time vs space evolution of a seismic swarm 

‐Mega‐earthquakes:g q

‐ Conclusions

DInSAR: how it works

Earthquakes studied in 1992-2012 (from Wright T.J. et al., 2013) based on the use of DInSAR

Satellite missions: state of art

Sentinel-1 IWSswath ~250 km

COSMO-SkyMed Stripmap swath ~40 km

~ 3 m average and up to 6.2 meters of right-lateral displacement

~ 25 cm of vertical displacement

InSAR derived seismic moment tends to be the larger than GCMT (Funning et al., 2007 L h d Si 2005 W i ht t l 1999) F i l (2002) t d2007; Lohman and Simons, 2005; Wright et al., 1999). Feigl (2002) reported differences of up to 60% between geodetically and seismically estimated moments.

The incl sion of interseismic triggered aseismic and post seismic deformation inThe inclusion of interseismic, triggered aseismic and post-seismic deformation in coseismic interferograms due to the longer measurement periods of geodetic data, were suggested as reasons for the trend.

In general, whenever we strictly refer to the coseismic moment release, there is a slight tendency for the moments calculated using InSAR data to be smaller than those reported in the GCMT cataloguethose reported in the GCMT catalogue.

strike-slippthrustnormal

Weston et al., 2012strike thrust normal

Trade‐off Magnitude‐Depth: which limitations for DInSAR 

Dawson and Tregoning, 2007g g

Small‐scale earthquakes: case studies

Katanning earthquake (10 October 2007, Mw 4.7 ) is a very shallow event

The earthquake rupture extends from a depth of around 640 m to the surface, making it a rarely

b d i t l t f t i tobserved intraplate, surface-rupturing event.

The average slip magnitude is 42 cm, over a rupture area of 1 km2rupture area of 1 km2.

Dawson et al., 2008

ALOS PALSAR 8ALOS PALSAR 8 September 2007 and 24 October 2007 (Fine Beam Double - FBD) mode.Double FBD) mode.

The perpendicular baseline between the repeat-pass satellite trajectories is 423 m.

Mw 4.4 composite Kalannie earthquake sequence (21–22 September 2005),

InSAR long-term time series analysis toimprove the measurement of the co-seismic i l i 27 i LOSsignal, maximum 27 mm in LOS

Dawson et al., 2008

ENVISAT ASAR C-band datasetincludes 24 descending and 14 ascending passes, observedfrom November 2004 to August 2007

“Picture” of time vs space evolution of a seismic swarm

EARTHQUAKE SWARMS:EARTHQUAKE SWARMS:sequences of earthquakes clustered in time and space, lacking a clear main shock(Mogi 1963; Sykes 1970; Hill 1977), covering an unusually large spatial arearelative to their total seismic moment release, and failing to decay in timerelative to their total seismic moment release, and failing to decay in timeaccording to standard aftershock scaling laws distinctive of main shock andaftershocks (Roland & McGuire 2009).

OBSERVED IN A VARIOUS RANGE OF GEOLOGICAL SETTINGS:volcanic (Bianco et al. 2004; Guglielmino et al. 2011)geothermal regions (Dziak et al. 2003)along transform plate boundaries and active rift zones (Baer et al. 2008; Pallister etal. 2010)associated with surface fault scarps and extensional cracks (Pollard et al. 1983;Rubin & Pollard 1988).

WHEN: In the period 2011 June–October, a tectonic swarm of nearly 1222 earthquakesdoccurred.

WHERE: The swarm occurred in the Messenia’s Upper Quaternary basin, 25 km NW of the cityof Kalamata, and migrated from NNW towards SSE.

EVENTS: The largest earthquakes occurred in 2011 August 14 (Mw = 4.8), September 14 (Mw= 4.6) and October 10 (Mw = 4.7), caused moderate structural damages mainly in old houses infour villages and produced particular unrest to the local population.

TECHNIQUE: We have investigated the monthly migration of the swarm using DifferentialSynthetic Aperture Radar Interferometry (DInSAR), presenting a very close look at thedeformation evolution that may reveal an aseismic slip component of the total movement.

RESULTS: The geodetically derived slip distribution for the first 4 months revealed that slipmigrated laterally along strike (north to south) and vertically from a deep portion, at 2.8 kmdepth, to a shallow portion, at less than 0.5 km, of the fault plane, and concluded its migrationt d th f ith h ll M 4 7 t f 2011 O t b 10towards the surface with a very shallow Mw 4.7 event of 2011 October 10.

SEISMIC MOMENT EVOLUTION and

AVAILABLE SAR IMAGES

OBSERVED SEISMICITYand

SWARM MIGRATION

From Kyriakopoulos et al., 2013, Geoph. J. Int

OCTOBERJULY AUGUST SEPTEMBER

A C D

B

AUG+SEPT NOV+DECJUL+AUG+SEPT JUL+AUG+SEPT+OCTAUG+SEPT NOV+DEC JUL+AUG+SEPT JUL+AUG+SEPT+OCT

E F HG

From Kyriakopoulos et al., 2013, Geoph. J. Int

On June 21st 2013 (10:33 UTC) a MwOn June 21st, 2013 (10:33 UTC), a Mw 5.3 (Ml 5.2) at about 5 km depth, north of the Apuan Alps, a mountain range of the Northern ApenninesNorthern Apennines.

- “Noisy” InSAR resultsNoisy InSAR results.- X- and C-band SAR data used.- Few cm (up to 3) displacement detected

Stramondo et al., 2014

X-band CSK images dated on June 21 and June 22, 2013 with a spatial baseline , pof 139 meters (asc orbit).

C-band RDR images dated on June 18 and July 12, 2013 with 69 m spatial baseline (asc orbit)

Mega‐earthquakes:

-A destructive (Mw 7.9) earthquake affected the Sichuan province (China) on May 12, 2008. ( ) y

- The seismic event ruptured approximately 270 km of the Yingxiu–Beichuan fault and about 70 km of the Guanxian–Anxian fault.

S f ff t ff d- Surface effects were suffered over a wide epicentral area (about 300 km E–W and 250 km N–S).

OUTLINE

Fukushima HamadoriFukushima Hamadori, Japan Earthquake (M7.0)

On-shore GPS (1200 sites) show that the coast of ( )northeast Japan moved 5m eastward, and the coastline subsided about 0.5m with a maximum subsidence of ~1.1m in the eastern Miyagi Prefecture.

InSAR measures up to 2.5 m LOS

On-shore data alone do not well constrain the source!

For the first time seafloor geodetic sites recordedFor the first time, seafloor geodetic sites recorded the offshore displacement for a megathrust event, allowing for unprecedented geodetic constraints on the source characterization.

Observations include horizontal displacements of ~24m and vertical displacements of 1.5–3m, over the hypocentral area.the hypocentral area.

Offshore geodetic sites precisely define the position of the polarity change for the offshore

ti l d f ti hi h t l t l thvertical deformation, which strongly controls the general depth of the estimated slip.

From Kyriakopoulos et al., 2013, Journ. Geoph. Research

Slip distribution, seafloor uplift and horizontal displacement (from top tohorizontal displacement (from top to bottom) for the heterogeneous (left) and the homogeneous (middle) model, respectively.p y

CONCLUSIONS

- DInSAR can be profitably used for a wide range of earthquake size (Mw), the lower threshold of detectable surface displacement is a function of surrounding conditions (SAR data used, hypocentral depth, topography,)

- The criteria for the selection of data is a critical issue: VHR SAR data suitable for moderate to small seisms, medium resolution SAR for large scale events

- The long history of DinSAR studies demonstrates the complementarity of this technique with respect to further geodetic data (GPS, Leveling, ...)

- Sentinel-1 (and the forthcoming S1b) is a versatile, novel, tool with an unprecedented compromise between wide area coverage and medium resolution Well suited for a large scale of earthquakesresolution. Well suited for a large scale of earthquakes