Tectonics Laboratory

Paul Lundgren, Susan Owen, Danan Dong, Eric Gurrola, Eric Fielding, Zhen Liu, Rowena Lohman,

Brian Newport, Paul Rosen, Frank WebbJet Propulsion Laboratory, California Institute of Technology

Fundamental science questions• How does strain accumulate along faults and plate

boundaries, and how is it released during the earthquake cycle?

• What are the appropriate rheological descriptions of the lithosphere that span different spatial and temporal scales?

• What is the relationship between observed short-term geodetic behavior and the formation of long-lived geologic structure?

• Focus on time variable deformation and fault mechanics in subduction and diffuse plate boundary zones.

• Combine high spatial and temporal resolution deformation maps over broad areas with geodynamic modeling.

Approach

Technology Development

• Bias-fixed high-rate GPS solutions– True coseismic deformation– Study transients on subdaily time scales

• Reprocessed GEONET data with new orbits, better troposheric mapping functions

– Better long term (decadal) transient detection.– Smaller seasonal signal in time series

• InSAR applications and processing development– InSAR time series development – scanSAR processing

• Incorporating InSAR time series into NIF– Critical for transient slip models using So Cal InSAR time series

Geodetic imaging of earthquake cycle deformation

Geodetic imaging of earthquake cycle deformation

Time series analysis challenges:-Common mode error

-Seasonal signals

-Sub-daily solutions

-Multiple changes in orbit analysis strategy over 10 years.

SoCal time series (preliminary)

InSAR time series using WInSAR archived ERS data.

Oil

Plate boundary profile

Santa Ana aquifer

Separate tracks require referencing to a common reference frame - either model-based or using GPS

Subduction Zone Processes

• Understanding nature of transient deformation– Transient slip detection using NIF– Study of large-spatial-scale Tokai transient

• Understand effects of non-uniform rheology on inversions for fault slip – Finite element models of elastic time scale events – Coseismic, short transient events.

• Understand interseismic plate coupling in Nankai segment – Inverse solutions based on FEM Greens fcns– Visco-elastic models combining realistic rheologies with great eq. recurrence

• Improving understanding of subduction zone fault mechanics, dynamics.– Integration of different time scale (transient, coseismic, interseismic) models.

Diffuse Plate Boundaries• Understand effects of non-uniform rheology on inversions for fault slip

– Coseismic, short transient events: Parkfield, Bam

• Understand nature of transient deformation.– Use combined InSAR and GPS time series to characterize transient events

• Generate an interseismic model for Southern Cal– Combined InSAR and GPS time series, with a FEM approach

• Understand source mechanisms of postseismic deformation– Use InSAR time series for Bam EQ postseismic– Compare with Parkfield and other recent large earthquakes

Eberhart-Phillips and Michael, 1993

Correlated noise Fault plane parameterization

Rigidity structure

Community fault model, SCEC

Imperial valley atmospheric noise

More accurate error bounds on earthquake/time series parameters

(Qeshm EQ location)

Bam 2003 coseismic slip

• preferred model two rupture planes

• main strike-slip fault beneath surface rupture and city

• second oblique thrust projects to surface fold previously mapped

• fits seismic waveform analysis

• nearly all slip shallower than 8 km Gareth Funning et al., JGR, 2005

Bam aftershocks

• aftershocks recorded by local network starting 3 days after 2003 quake

• strong motion data from Bam show strong directivity to city

• aftershocks all > 6 km, dip west, extend to 20 km

• illuminate unruptured deeper fault so continued risk for cityJackson, Bouchon, Fielding et al., GJI,

Sept. 2006

Postseismictime series

• Descending track 120, 20 epochs Jan. 2004–Mar. 2006, also two ascending tracks

• 44 interferograms

• plane fit removed from each epoch

• referenced to epoch 3 (Mar. 2004) with less atmospheric noise

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are needed to see this picture.

Post-seismic processes depend

on t time since Bam earthquake

2) s + A (1–exp(-t/τ))

s -1.4 cmA 2.6 cmτ 0.45 y

s is deformation from EQ to ref.

2004/3/17

A is deformation from EQ to

infinity

τ is time constant

1) a + b log(t)

west lookingtrack

Shallow afterslip model

North South

Dep

th (

km)

UTM northing (km)

more at AGU postseismic session

SCIGN stations 3-D fault model (remeshed from CFM)

Triangular Network Inversion Filter

San Andreas fault region – transient slip rate Jan. 2001- June. 2006

NW

SE

Increase of N-S contraction rate in northern Los Angeles Basin

Transient deformation around the onshore Oakridge fault in Ventura Basin

E,N,U comp. of position time seriesat GPS station VNCO

Inverted cum. Slip fromNetwork inversion filter

Map view of the deviation from linear trend

1.913.6

-0.274.0

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9.39 7.27 nanostrain/yr2

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Strain rate tensor time series

Thanks, and come see our posters!

Available dense GPS networks

Crustal strain vs time (sec, hours, days, years)• interseismic, preseismic (?), coseismic, postseismic, mechanics

Postseismic time series

Descending track (west look)

Relationship to JPL Strategic Goals

• Enhances InSAR and GPS core competency for the Lab in science and technology areas that have suffered from lack of NASA sponsorship, offsetting deficiencies in these areas and setting the stage for a Solid Earth InSAR mission and advanced GNSS science applications.

• Developing the technological infrastructure to maintain JPL science in the forefront of geodynamics research

– InSAR time series– InSAR scan-SAR interferometry– Integration into mROI_PAC– High-rate GPS solutions from large networks– GPS analysis using cluster computing– GNSS capability

• Builds up solid Earth science at the Lab – Broadens and deepens JPL science in plate boundary processes research.– Enhances numerical modeling capabilities in geodynamics

• Hired two post-docs with expertise in geodynamic modeling of plate boundaries• Acquiring state-of-the-art finite element and Network Inversion Filter modeling capabilities

– Addressing the key scientific questions of time varying plate boundary deformation and mechanics• Time varying fault and mechanical models for California and western US• Plate coupling and transient slip models in Japan subduction zone• Postseismic deformation and implications for lithospheric rheology (Bam, Landers, Hector Mine, Parkfield)

• Will strengthen our ties with Caltech and the Tectonic Observatory– Collaboration on

• Modeling (scientific interaction, postdoc selection, meshing and FEM capabilities)• Time series analysis (GEONET analysis, cluster computing, periodic signal analysis)

– Building a team with Caltech based on• JPL researchers, Caltech Faculty, JPL and Caltech Post-docs, and computational infrastructure.

• Strengthens our position for lead science role on space geodesy missions, such as an InSAR mission – Will strategically position JPL to play a major role in NSF PBO research and in future NASA missions