NS

Looking Inside the Continents from Space: Insights into Earthquake Hazard and

Crustal Deformation

NS

IndiaTibetan Plateau5 cm/yr

Earthquake Hazard in the Alpine-Himalayan Belt

Alpine-Himalayan Belt

75% of earthquakes killing more than 10k since 1900.

Mapping Surface Deformation (Strain)

• Although they can not be predicted, earthquakes are preceded by the slow build up of tectonic strain.

• Repeated satellite radar measurement can be combined to measure surface displacements at the mm level over large areas.

• The team have pioneered methods for mapping deformation using satellite radar.

• A radical increase in radar data quality and quantity from the Sentinel-1 mission will allow strain to be mapped with high accuracy over large regions for the first time.

Wright, Parsons & Fielding, GRL 2001

0

6

-6

mm/yr

North Anatolian Fault, 23 mm/yr

Objectives

A: Make fundamental advance in the mapping of tectonic deformation (for

Alpine-Himalayan Belt and East African Rift)

B: Improve seismic hazard

assessment

C: Understand how the continents deform

in space and time

Basic Question 1: What is the Mechanical Structure of Fault Zones Controlling the Earthquake Cycle

~20 mm/yr

Postseismic, 1997 Manyi EarthquakeRyder, Parsons, Wright & Funning, GJI, 2007

LOS

disp

lace

men

t (cm

)Poro-elasticity

Visco-elastic relaxation

Afterslip

0

4

-4

cm

Earthquakes with Mw ≥ 6.7. Black: 1991-2012 (InSAR era); Red: 1978-1991

Poro-elasticity

Visco-elastic relaxation

Afterslip

• Modelling the earthquake cycle has been hampered by the lack of observations (relatively few events where data available + short time periods compared to length of cycle)

• We will build and test dynamical models of the earthquake cycle, constrained by observations of different parts of faults at different stages in the cycle

Basic Question 1: What is the Mechanical Structure of Fault Zones Controlling the Earthquake Cycle

x

y

Red = weak lower crustBlack = strong lower crust

Horizontal

VerticalBasic Question 2: What is the Mechanical Structure of

Continental Lithosphere?

Copley, 2008

a

ba b

Accuracy Requirements and Earthquake Hazard

• 96% of all earthquake deaths are in regions with strain rates greater than 1mm/yr over 100 km (10-8/yr)

• 77% of fatalities occur where deformation rates are ≤ 5 mm/yr over 100 km.

Cum

ulati

ve p

erce

ntag

e of

ear

thqu

ake

deat

hs

Magnitude of tectonic strain (x10-9 /yr)

Sentinel-1 makes this possible

Envisat Sentinel-1

Stand-alone mission not specifically designed for InSAR

20 year operational program, designed for InSAR

Haphazard acquisition strategy (multiple modes)

Systematic acquisitions over deformation belts

Archive typically has ~30 images over 7 years

12 day revisit → 30 images per satellite per year

Loss of signal due to long time gaps or large orbital separations

6 day revisit (with two satellites), small orbital separation

Achieving 1 mm/yr accuracy

Wang, Wright et al, 2008

Accurate Orbital Models

Atmospheric Corrections

0

5

-5

mm/yr

Achieving 1 mm/yr accuracy

Wang, Wright et al, 2008

Error for mission with 12-day repeat

Duration of time series (years)

Leng

th s

cale

of o

bser

vatio

n (k

m)

0

5

-5

mm/yr

Wang & Wright, GRL 2012

Producing High-resolution Velocity and Strain Fields from InSAR and GPS

East Velocity Strain

17/11/12

SRTM Digital elevation data

N

10 km

Lepsy fault

Single event? Length 100 km, slip 10 m .....Magnitude 8.0

10 m

Richard Walker, pers comm

++

++

+ +

Identifying previously unknown faults with high-resolution imagery and DEMs

Lepsy fault, Kazakhstan (Walker, Jackson et al, in preparation)

The TeamW

right

Tectonic DeformationA1: InSAR Time Series [Leeds: Wright, Hooper, PDRA #1]A2: Atmospheric Errors [Glasgow: Li, PDRA #2; Reading: Wadge]A3: Orbital Errors [UCL: Ziebart, PDRA #3]Seismic HazardB4: Strain/Hazard Mapping [Leeds: Wright, Walters (COMET+ PDRA #4)]B5: Finding Faults [Oxford: Walker, PDRA #5; Cambridge: Jackson]B6: Time-dependent Hazard [Oxford: England, Elliott (COMET+ PDRA #6), Parsons]ModellingC7: Earthquake Cycle Models [Oxford: Parsons, PDRA #7; Leeds: Houseman, Wright]C8: 3D Numerical Modelling [Cambridge: Copley; Leeds: Houseman; Oxford: England]C9: East African Rift [Bristol: Biggs; Reading: Wadge]

Pars

ons

Plus 5 PhD students, Partner Nocquet (GPS)

Impact Partners

Why us? Why now? Ambitious, Frontier Science

Velocity and strain fields and resultant models will transform our understanding of continental deformation.

Timely Exploits radical increase in SAR data from the Sentinel-1

mission, an opportunity for leadership in this field.

Achievable Builds on more than a decade of development by the

investigators.

Societal Impact Accurate knowledge of the distribution of seismic hazard is

the first step in hazard mitigation.

High-resolution deformation

measurements from Sentinel-1

Earthquake Hazard

Earthquake source models

Precise Orbits for Sentinel-1

Water Vapour measurements

Earthquake Cycle Deformation Models

Regional Strain Maps

Fault Map for Alpine-

Himalayan Belt

3D Models of Continental Tectonics

What this project will deliverData

Derived products

Models

Information

Q. Management

Q. What will the students do?Student #1: Copley, Jackson (Cambridge)Constraining the structure and rheology of the lithosphere(Using satellite gravity and seismic structure to investigate thermal and rheological structure of the lithosphere)Student #2: Jackson, Copley (Cambridge), Elliott (Oxford)Active faulting and rift evolution in East Africa(Analysing DEMs and Optical imagery to investigate faulting in EAR. Linking this to variations in lithospheric thickness and mantle structure, and to mechanisms of recent seismic activity derived from InSAR/seismology)Student #3: Houseman, Wright (Leeds)Mechanisms of strain localisation in the Crust(Developing 2D and 3D FEMs that include anisotropic viscoelastic constitutive relationships,due to CPO, and feedback mechanisms) Student #4: Hooper (Leeds), Biggs (Bristol)Automatic detection of volcanic unrest(Applying techniques developed in the proposal to volcanic deformation on a large scale) Student #5: Biggs (Bristol), Wadge (Reading)Active volcanism and magma intrusion in East Africa(testing whether ratio of extrusion/intrusion in the crust is a function of degree of crustal extension)

Technical challenges:• Solar and Earth radiation photon pressure modelling• Atmospheric drag• Antenna thrust (recoil forces from signal transmission)• GPS phase centre determination/multipath modelling• Orbit product validation (laser ranging residual analysis, repeatability)

True trajectoryBiased orbit (mismodelled dynamics)

5cm error

JPL/UCL orbit (1cm accuracy)

Jason-1

Sentinel-1

Q. Can we be confident of

achieving 1cm orbital precision?

Q. How well can we remove atmospheric noise?

Jolivet et al., 2011

We assume, conservatively, that weather models will correct 50% of single interferograms

Q. Can we really estimate water vapour in near-real time?

For N=15, error in path delay ~ 2 mm; For N=100 (~3 years), error ~1 mm

Q. Will it be coherent at C-band?

C-band coherence (1 year = red; 1 cycle = red+orange)L-band should be coherence in most places over 13 days

Wright et al., Fringe 2011

Q. Why East Africa?C

raig

, Ja

ckso

n et

al.,

201

1

Lithospheric thickness

Ham

mon

d et

al.,

201

3

Shear-wave anomaly (75 km)

Q. How much better than existing missions?

Envisat Data, 70 Day Repeat, 7 years data

Sentinel-1A Data, 12 Day Repeat, 3 years data

40% of areas straining above

10-8 yr-1

80% of areas straining above 10-8 yr-1 [90 %

with two satellites]

Wright et al., Fringe 2011

Q. How to turn strain into hazard maps?

Number of earthquakes forecast with M > 5.66, from Bird et al., 2010. Green = 1 earthquake per century in a 100 x 100 km area .[Crude because strain data is low resolution]

Q. Time dependent Hazard?

3 September 2010: Darfield, M7.1

21 February 2011: Christchurch, M6.3

New Zealand Earthquakes 2010-11