antonella cirella, alessio piatanesi, elisa tinti, massimo cocco ground motion and source process of...

Antonella Antonella Cirella,Cirella,

Alessio Alessio Piatanesi, Piatanesi,

Elisa Tinti, Elisa Tinti,

Massimo CoccoMassimo Cocco

Ground Motion and Source Process of theGround Motion and Source Process of the66th th April 2009 L’Aquila, central Italy, EarthquakeApril 2009 L’Aquila, central Italy, Earthquake

NERA Project- JRA3 (WP13) : INGV, Roma, 17-NERA Project- JRA3 (WP13) : INGV, Roma, 17-18 May 201118 May 2011

INGV

1.1. Global search kinematic inversion technique of Global search kinematic inversion technique of seismological & geodetic data;seismological & geodetic data;

2. We retrieve the rupture process of the 2009 April 62. We retrieve the rupture process of the 2009 April 6thth L’Aquila, central Italy, mainshock (ML’Aquila, central Italy, mainshock (Mww 6.1), by using a 6.1), by using a nonlinear separate and joint inversions of strong nonlinear separate and joint inversions of strong motion, GPS, DInSAR data;motion, GPS, DInSAR data;

3. In order to capture the heterogeneity of the rupture 3. In order to capture the heterogeneity of the rupture history, we give particular attention to the history, we give particular attention to the variability of model parameters and we attempt to variability of model parameters and we attempt to constrain the local rupture velocity on the fault constrain the local rupture velocity on the fault plane;plane;

4. The goal is to constrain the mechanics of the 4. The goal is to constrain the mechanics of the causative fault as well as the observed ground motion.causative fault as well as the observed ground motion.

GoalsGoals


joint and separate inversion of strong motion, GPS joint and separate inversion of strong motion, GPS and DInSAR data;and DInSAR data;

several analytical slip several analytical slip velocity source velocity source time functions (STFs) are time functions (STFs) are implemented;implemented;

finite fault is divided into finite fault is divided into sub-faults;sub-faults;

Inverted Inverted Parameters:Parameters:

•Peak Slip Peak Slip Velocity;Velocity;

•Rise Time;Rise Time;

•Rupture Time;Rupture Time;

•Rake.Rake.

kinematic parameters are kinematic parameters are allowed allowed to vary within a sub-to vary within a sub-fault;fault;

different crustal models can be different crustal models can be adopted adopted to compute Green's functions at to compute Green's functions at different receivers.different receivers.

Kinematic Inversion TechniqueKinematic Inversion TechniqueData & Fault ParameterizationData & Fault Parameterization

Kinematic Inversion TechniqueKinematic Inversion TechniqueData & Fault ParameterizationData & Fault Parameterization

models having a local rupture models having a local rupture velocityvelocity larger than P-wave velocity larger than P-wave velocity are discardedare discarded (not acausal rupture (not acausal rupture propagation);propagation);


Kinematic Inversion TechniqueKinematic Inversion TechniqueOutputOutput

Kinematic Inversion TechniqueKinematic Inversion TechniqueOutputOutput

Best Model Best Model

Average Model:Average Model:

Standard Deviation:Standard Deviation:

Output of kinematic Output of kinematic inversion:inversion:

ΩΩ

Model EnsembleModel Ensemble ΩΩ = = Rupture Models Rupture Models m m &&

Cost Function Cost Function C(m)C(m)


1.1. The 2009 L’Aquila earthquake (MThe 2009 L’Aquila earthquake (Mww 6.1) occurred 6.1) occurred in the Central Apennines (Italy) on April 6in the Central Apennines (Italy) on April 6thth at the 01:32 UTC and caused nearly 300 at the 01:32 UTC and caused nearly 300 casualties and heavy damages in the L’Aquila casualties and heavy damages in the L’Aquila town and in several villages nearby.town and in several villages nearby.

2.2. The main shock ruptured a normal fault The main shock ruptured a normal fault striking along the Apennine axis and dipping striking along the Apennine axis and dipping at nearly 50° to the SW. Most of the at nearly 50° to the SW. Most of the aftershocks are also associated with normal aftershocks are also associated with normal faulting, which is consistent with the faulting, which is consistent with the present-day tectonic setting of this sector of present-day tectonic setting of this sector of the Apennines.the Apennines.

2009 L’Aquila (central Italy) 2009 L’Aquila (central Italy) Earthquake, MEarthquake, Mww=6.1=6.1



DatasetDatasets:s: 2009 April 62009 April 6th th 1:32 1:32

UTCUTC 14 accelerograms 14 accelerograms (strong motion records (strong motion records from the RAN and the from the RAN and the MedNet station AQU);MedNet station AQU);

36 GPS stations 36 GPS stations (INGV-Ring, GNSSA, (INGV-Ring, GNSSA, ISPRA, ITALPOS and ASI ISPRA, ITALPOS and ASI network, network, Cheloni & al, Cheloni & al, 20102010););

70 km;70 km;

frequency-band: frequency-band: (0.02÷0.5) Hz; (0.02÷0.5) Hz;

60 sec (body & surface 60 sec (body & surface waves);waves);



InputInput


DInSARDInSAR Satellite: Envisat

descending. SAR Sensor: C-band, wavelength = 5.6 cm, look angle: 23°;

Each fringe represents a deformation of 2.8 cm in Line of Sight (LOS).

The images have been acquired on April 27, 2008 and April 12, 2009, respectively.

In green the 2625 resampled pixels (size=300 m) selected for the inversion.

InputInput


Crustal StructureCrustal Structure

Receiver function:Receiver function: 1D velocity model resulting from 1D velocity model resulting from the analysis of receiver functions at AQU & AQG sites the analysis of receiver functions at AQU & AQG sites ((Bianchi & al., 2010Bianchi & al., 2010). Used to compute synthetics at ). Used to compute synthetics at AQU and AQG.AQU and AQG.

nnCIA.mod:nnCIA.mod: 1D velocity model resulting from the 1D velocity model resulting from the surface wave dispersion analysis (surface wave dispersion analysis (Herrmann & Malagnini, Herrmann & Malagnini, 20092009). Used to compute synthetics at all other ). Used to compute synthetics at all other stations.stations.

InputInput


Fault Fault GeometryGeometry

hypocenter: 42.35°N, 13.38°E, 9.5km depth hypocenter: 42.35°N, 13.38°E, 9.5km depth ((Chiarabba et al., 2009Chiarabba et al., 2009););

strike: N133°E;strike: N133°E;

dip: 54° to SW; dip: 54° to SW;

all kinematic parameters are inverted all kinematic parameters are inverted simultaneouslysimultaneously (0-3.5) m/s psv; (0.75-3)s (0-3.5) m/s psv; (0.75-3)s ; (1.4-4.0)km/s vr; ; (1.4-4.0)km/s vr; (230-310)° rake angle.(230-310)° rake angle.

Fault ParametrizationFault Parametrization W=17.5km; L= 28km; W=17.5km; L= 28km; =3.5km;=3.5km;

The proposed fault The proposed fault geometry agrees with the geometry agrees with the DInSAR data and the DInSAR data and the aftershock pattern. It is aftershock pattern. It is also consistent with both the also consistent with both the hypocenter location and the hypocenter location and the induced surface breakages. induced surface breakages.

InputInput


Inversion Results - Rupture Inversion Results - Rupture HistoryHistory

OutputOutput


Inversion Results - Slip Inversion Results - Slip Velocity HistoryVelocity History

QuickTime™ e undecompressore H.264

sono necessari per visualizzare quest'immagine.

OutputOutput


Local Rupture Velocity & Rupture Index Local Rupture Velocity & Rupture Index ModeMode

OutputOutput

€

rup = 1− 2ϕ ij

π

Pulido & Dalguer (2009)


We investigate the rupture history of the 2009 We investigate the rupture history of the 2009 L’Aquila (Central Italy) earthquake using a nonlinear L’Aquila (Central Italy) earthquake using a nonlinear inversion of strong motion, GPS and DInSAR data. inversion of strong motion, GPS and DInSAR data.

Both the separate and joint inversions reveal a Both the separate and joint inversions reveal a complex rupture history and a heterogeneous slip complex rupture history and a heterogeneous slip distribution characterized by a shallow slip patch distribution characterized by a shallow slip patch located up-dip from the hypocenter and a large, located up-dip from the hypocenter and a large, deeper patch located southeastward. deeper patch located southeastward.

The rupture history is characterized by two distinct The rupture history is characterized by two distinct phases: a rupture initiation with a modest moment phases: a rupture initiation with a modest moment release lasting nearly 0.5 sec, followed by a sharp release lasting nearly 0.5 sec, followed by a sharp increase in slip velocity and rupture speed (4.0 increase in slip velocity and rupture speed (4.0 km/s) located 2 km up-dip from the hypocenter and a km/s) located 2 km up-dip from the hypocenter and a second stage (starting 2.0 sec after the nucleation) second stage (starting 2.0 sec after the nucleation) characterized by a slower along strike rupture characterized by a slower along strike rupture propagation and the failure of the deep larger slip propagation and the failure of the deep larger slip patch. patch.

The up-dip and along-strike rupture propagations are The up-dip and along-strike rupture propagations are separated in time and associated with two distinct separated in time and associated with two distinct rupture modes: Mode II and Mode III, respectively.rupture modes: Mode II and Mode III, respectively.

ConclusionsConclusions


Our rupture model confirms the evident along strike Our rupture model confirms the evident along strike directivity (directivity (Pino&Di LuccioPino&Di Luccio (2009), (2009), Akinci&al Akinci&al (2010)) and it also reveals an initial up-dip (2010)) and it also reveals an initial up-dip directivity that lasted for nearly 2sec and likely directivity that lasted for nearly 2sec and likely affected the ground motion observed in the L’Aquila affected the ground motion observed in the L’Aquila town;town;

Our results show that the 2009 L’Aquila mainshock Our results show that the 2009 L’Aquila mainshock featured a very complex rupture history for a featured a very complex rupture history for a moderate Mmoderate Mww 6.1, with strong spatial and temporal 6.1, with strong spatial and temporal heterogeneities suggesting a strong frictional heterogeneities suggesting a strong frictional properties’ control of the rupture process.properties’ control of the rupture process.

Cirella, A., A.Piatanesi, E. Tinti, M.Chini and M.Cocco, Source Cirella, A., A.Piatanesi, E. Tinti, M.Chini and M.Cocco, Source Complexity of the 2009 L’Aquila, Italy, earthquake: Evidence for a Complexity of the 2009 L’Aquila, Italy, earthquake: Evidence for a Rheological Control on Rupture Process, submitted to Rheological Control on Rupture Process, submitted to Geophysical Journal Geophysical Journal InternationalInternational..Cirella, A., A.Piatanesi, M.Cocco, E. Tinti, L. Scognamiglio, A. Cirella, A., A.Piatanesi, M.Cocco, E. Tinti, L. Scognamiglio, A. Michelini, A. Lomax and E.Boschi (2009), Rupture history of the 2009 Michelini, A. Lomax and E.Boschi (2009), Rupture history of the 2009 L'Aquila (Italy) earthquake from non-linear joint inversion of strong L'Aquila (Italy) earthquake from non-linear joint inversion of strong motion and GPS data, motion and GPS data, Geophys. Res. LettGeophys. Res. Lett., 36, L19304, ., 36, L19304, doi:10.1029/2009GL039795doi:10.1029/2009GL039795

..for details see..


ConclusionsConclusions

Slip Velocity History-Slip Velocity History-DirectivityDirectivity

QuickTime™ e undecompressore H.264

sono necessari per visualizzare quest'immagine.

To investigate the relationship between the observed To investigate the relationship between the observed ground motion variability & the kinematic source ground motion variability & the kinematic source parameters taking into account the strong parameters taking into account the strong heterogeneity of the rupture process;heterogeneity of the rupture process;

To study the effects of the observed directivity;To study the effects of the observed directivity;

To better analyze the effect of frictional properties To better analyze the effect of frictional properties on the retrieved rupture history;on the retrieved rupture history;

These aspects are crucial to generate & to interpret These aspects are crucial to generate & to interpret shaking scenarios in near source regions.shaking scenarios in near source regions.

Key IssuesKey Issues

This afternoon..This afternoon..13:45 – 14:00 Task 2 “Identification of ground motion dominated 13:45 – 14:00 Task 2 “Identification of ground motion dominated by the source” (A. Piatanesi - INGV) by the source” (A. Piatanesi - INGV)


Kinematic Inversion TechniqueKinematic Inversion TechniqueStage I: Building-up the Model EnsembleStage I: Building-up the Model Ensemble

Kinematic Inversion TechniqueKinematic Inversion TechniqueStage I: Building-up the Model EnsembleStage I: Building-up the Model Ensemble

random model m0random model m0STARTSTART

+=Strong motion L1+L2 norm

To quantify the misfit…

GPSL2 norm

C(m)C(m)

DInSARL2 norm

+

Forward Modeling: CompsynForward Modeling: CompsynMisfit computationMisfit computation

Loop over parameters (Vr,…)Loop over parameters (Vr,…)Loop over model valuesLoop over model values

Loop over iterationsLoop over iterationsLoop over temperaturesLoop over temperatures

endend

endend

Simulated annealingHeat-bath algorithm

AuxAux


Inversion Results - Inversion Results - DataFitDataFit

AuxAux


Inversion Results - DataFit only DInSAR Inversion Results - DataFit only DInSAR & only GPS& only GPS

AuxAux

Inversion Results - Inversion Results - DataFit: only SMDataFit: only SM

AuxAux


Inversion Results -

Inversion Results -

Snapshots

Snapshots

AuxAux


2009 L’Aquila (Central Italy) Earthquake, M2009 L’Aquila (Central Italy) Earthquake, Mww=6.1=6.1

Rupture Process & on-fault Seismicity Pattern Rupture Process & on-fault Seismicity Pattern


€

ru = ∇t =

∂t

∂x

√ x +

∂t

∂y

√ y

€

rV rij

=cosϕ ij

∇tij

√ x +sinϕ ij

∇tij

√ y

is the angle between the rupture velocity vector and the fault strike direction

€

ϕ ij = tan−1 ∇tij ⋅ √ y ∇tij ⋅ √ x ( )


antonella cirella, alessio piatanesi, elisa tinti, massimo cocco ground motion and source process of...

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inputnera project jra3

goalsnera project jra3

rupture models

d velocity model

laquila earthquake mw

rupture process

central apennines italy

local rupture velocity