slide1
Download
Skip this Video
Download Presentation
Antonella Cirella, Alessio Piatanesi, Elisa Tinti, Massimo Cocco

Loading in 2 Seconds...

play fullscreen
1 / 24

Antonella Cirella, Alessio Piatanesi, Elisa Tinti, Massimo Cocco - PowerPoint PPT Presentation


  • 146 Views
  • Uploaded on

INGV. Ground Motion and Source Process of the 6 th April 2009 L’Aquila, central Italy, Earthquake. Antonella Cirella, Alessio Piatanesi, Elisa Tinti, Massimo Cocco. NERA Project- JRA3 (WP13) : INGV, Roma, 17-18 May 2011. Goals.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about ' Antonella Cirella, Alessio Piatanesi, Elisa Tinti, Massimo Cocco' - yaron


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
slide1

INGV

Ground Motion and Source Process of the

6th April 2009 L’Aquila, central Italy, Earthquake

Antonella Cirella,

Alessio Piatanesi,

Elisa Tinti,

Massimo Cocco

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

slide2

Goals

Global search kinematic inversion technique of seismological & geodetic data;

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

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

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

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

slide3

Kinematic Inversion TechniqueData & Fault Parameterization

  • finite fault is divided into sub-faults;
  • Inverted Parameters:
  • Peak Slip Velocity;
  • Rise Time;
  • Rupture Time;
  • Rake.
  • joint and separate inversion of strong motion, GPS and DInSAR data;
  • kinematic parameters are allowed

to vary within a sub-fault;

  • models having a local rupture velocity

larger than P-wave velocity are discarded

(not acausal rupture propagation);

  • several analytical slip velocity source

time functions (STFs) are implemented;

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

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

slide4

Kinematic Inversion TechniqueOutput

  • Average Model:
  • Standard Deviation:

Output of kinematic inversion:

Ω

Rupture Models m

&

Cost Function C(m)

Model EnsembleΩ =

  • Best Model

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

slide5

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

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

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

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

slide6

Input

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

Datasets:

2009 April 6th 1:32 UTC

  • 14 accelerograms (strong motion records from the RAN and the MedNet station AQU);
  • 36 GPS stations (INGV-Ring, GNSSA, ISPRA, ITALPOS and ASI network, Cheloni & al, 2010);
  •   70 km;
  • frequency-band: (0.02÷0.5) Hz;
  • 60 sec (body & surface waves);

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

slide7

Input

DInSAR

  • 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.

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

slide8

Crustal Structure

Input

  • Receiver function: 1D velocity model resulting from the analysis of receiver functions at AQU & AQG sites (Bianchi & al., 2010). Used to compute synthetics at AQU and AQG.
  • nnCIA.mod: 1D velocity model resulting from the surface wave dispersion analysis (Herrmann & Malagnini, 2009). Used to compute synthetics at all other stations.

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

slide9

Fault Geometry

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

Fault Parametrization

  • W=17.5km; L= 28km; =3.5km;
  • all kinematic parameters are inverted simultaneously
  • (0-3.5) m/s psv; (0.75-3)s ; (1.4-4.0)km/s vr; (230-310)° rake angle.

Input

  • hypocenter: 42.35°N, 13.38°E, 9.5km depth (Chiarabba et al., 2009);
  • strike: N133°E;
  • dip: 54° to SW;

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

slide10

Inversion Results - Rupture History

Output

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

slide11

Output

Inversion Results - Slip Velocity History

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

slide12

Output

Local Rupture Velocity & Rupture Index Mode

Pulido & Dalguer (2009)

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

slide13

Conclusions

  • We investigate the rupture history of the 2009 L’Aquila (Central Italy) earthquake using a nonlinear inversion of strong motion, GPS and DInSAR data.
  • Both the separate and joint inversions reveal a complex rupture history and a heterogeneous slip distribution characterized by a shallow slip patch located up-dip from the hypocenter and a large, deeper patch located southeastward.
  • The rupture history is characterized by two distinct phases: a rupture initiation with a modest moment release lasting nearly 0.5 sec, followed by a sharp increase in slip velocity and rupture speed (4.0 km/s) located 2 km up-dip from the hypocenter and a second stage (starting 2.0 sec after the nucleation) characterized by a slower along strike rupture propagation and the failure of the deep larger slip patch.
  • The up-dip and along-strike rupture propagations are separated in time and associated with two distinct rupture modes: Mode II and Mode III, respectively.

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

slide14

Conclusions

Cirella, A., A.Piatanesi, E. Tinti, M.Chini and M.Cocco, Source Complexity of the 2009 L’Aquila, Italy, earthquake: Evidence for a Rheological Control on Rupture Process, submitted to Geophysical Journal International.

Cirella, A., A.Piatanesi, M.Cocco, E. Tinti, L. Scognamiglio, A. Michelini, A. Lomax and E.Boschi (2009), Rupture history of the 2009 L\'Aquila (Italy) earthquake from non-linear joint inversion of strong motion and GPS data, Geophys. Res. Lett., 36, L19304, doi:10.1029/2009GL039795

  • Our rupture model confirms the evident along strike directivity (Pino&Di Luccio (2009), Akinci&al (2010)) and it also reveals an initial up-dip directivity that lasted for nearly 2sec and likely affected the ground motion observed in the L’Aquila town;
  • Our results show that the 2009 L’Aquila mainshock featured a very complex rupture history for a moderate Mw 6.1, with strong spatial and temporal heterogeneities suggesting a strong frictional properties’ control of the rupture process.

..for details see..

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

slide16

Key Issues

  • To investigate the relationship between the observed ground motion variability & the kinematic source parameters taking into account the strong heterogeneity of the rupture process;
  • To study the effects of the observed directivity;
  • To better analyze the effect of frictional properties on the retrieved rupture history;
  • These aspects are crucial to generate & to interpret shaking scenarios in near source regions.

This afternoon..

13:45 – 14:00 Task 2 “Identification of ground motion dominated

by the source” (A. Piatanesi - INGV)

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

slide18

Kinematic Inversion TechniqueStage I: Building-up the Model Ensemble

START

random model m0

Loop over temperatures

Loop over iterations

Loop over parameters (Vr,…)

Loop over model values

Simulated annealing

Heat-bath algorithm

Forward Modeling: Compsyn

Misfit computation

end

end

end

To quantify the misfit…

end

Strong motionL1+L2 norm

DInSAR

L2

norm

GPS

L2

norm

=

C(m)

+

+

Aux

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

slide19

Aux

Inversion Results - DataFit

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

slide20

Aux

Inversion Results - DataFit only DInSAR & only GPS

slide21

Aux

Inversion Results - DataFit: only SM

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

slide22

Aux

Inversion Results - Snapshots

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

slide23

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

Rupture Process & on-fault Seismicity Pattern

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

slide24

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

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

ad