1. Looking Inside the Continents from Space: Insights into Earthquake Hazard and Crustal Deformation

2. India
Tibetan Plateau
5 cm/yr S N

3. Earthquake Hazard in the Alpine-Himalayan Belt
75% of earthquakes killing more than 10k since 1900.
. Each of these circles is an earthquake that has killed more than 10,000 people.
. 35 since 1900.
. [click] 26 of these, including 4 in the 21st century, have been in the broad zone of continental deformation spanning from Italy to China – the Alpine-Himalayan Belt.
. Most occurred on faults that had previously been unidentified or whose hazard underestimated.
. Although short-term earthquake prediction seems impossible, all earthquakes are preceded by the slow build up of tectonic strain. 3

4. Mapping Surface Deformation (Strain)
North Anatolian Fault, 23 mm/yr
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. 6 -6
mm/yr
COMET has pioneered methods for mapping such surface strain – the map on the left shows deformation in Turkey around the North Anatolian Fault, and was the first measurement of tectonic strain made completely remotely from space.
About 20 interseismic strain accumulation studies in the Alpine Himalayan belt.
The radical increase in the quality and quantity of radar data from the EC Sentinel-1 mission, due for launch next year, combined with large archives of existing data, now allow strain to be mapped over large regions.
This project will exploit these methods and data sets to test physical models of the earthquake cycle and continental deformation, and to radically improve seismic hazard maps
ADD ashkabad figfure from rich
Wright, Parsons & Fielding, GRL 2001

5. Objectives B: Improve seismic hazard assessment
A: Make fundamental advance in the mapping of tectonic deformation (for Alpine-Himalayan Belt and East African Rift)
This project will deliver the first high resolution strain maps for the AHB and EAR. To obtain an equivalent result with ground-based instruments would require on the order of 100,000 instruments.
We will use these measurements, informed by these models, to produce an improved seismic hazard assessment.
Spatial variations in the strain will be used to constrain 2D and 3D models of variations in the properties of the lithosphere throughout the region,
and variations in space and time will be used to constrain models of the earthquake loading cycle.
C: Understand how the continents deform in space and time

6. Basic Question 1: What is the Mechanical Structure of Fault Zones Controlling the Earthquake Cycle4 -4 cm
LOS displacement (cm)
~20 mm/yr
Poro-elasticity
Visco-elastic relaxation
Afterslip
Deformation isn’t always steady state. Here is the postseismic deformation measured in the year following the Manyi earthquake.
Rates are as high as 20 mm/yr initially, decaying back to an intereseismic deformation rate of <5 mm /yr.
The way strain and hence stress is distributed around earthquake faults depends on the mechanical structure of the medium. Can determine through constructing models of the earthquake cycle.
Simple models cannot explain both the rapid postseismic deformation observed in places like Manyi, and the focused interseismic strain seen around most faults
Postseismic, 1997 Manyi Earthquake
Ryder, Parsons, Wright & Funning, GJI, 2007

7. Basic Question 1: What is the Mechanical Structure of Fault Zones Controlling the Earthquake Cycle
Earthquakes with Mw ≥ 6.7. Black: (InSAR era); Red:
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
Poro-elasticity
Visco-elastic relaxation
Afterslip
Instead of being limited to studies of a few faults, we will have data from thousands. This is despearately needed if we are to make progress in understanding cyclical strain associated with earthquakes.

8. Basic Question 2: What is the Mechanical Structure of Continental Lithosphere?
Horizontal y
Red = weak lower crust
Black = strong lower crust x
We also require high resolution, high accuracy measurements of surface deformation to make advances in our understanding of continental tectonics.
As an example, one of the current major controversies in continental tectonics is whether there is a low viscosity region in the lower crust of Tibet.
These two models for deformation in SE Tibet from co-investigator Alex Copley shows that the pattern of horizontal movement is relatively insensitive to the strength of the lower crust. Accurate measurements of vertical deformation, however, can enable these models to be discriminated.
To do this also requires dense displacement measurements with an accuracy of ~1 mm/yr. a b b
Vertical
Copley, 2008

9. Accuracy Requirements and Earthquake Hazard
Cumulative percentage
of earthquake deaths
This graph shows the relationship between the number of casualties in earthquakes and the magnitude of tectonic strain, as estimated from the existing low-resolution global model.
The cumulative histogram in grey shows 96% of all earthquake deaths occur in regions that are straining at rates above 1.2 x 10-8 yr-1 (1mm/yr over 100 km). 77% of deadly earthquakes occur where deformation rates are less than 5 mm/yr.
Magnitude of tectonic strain (x10-9 /yr)
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.

10. 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
Also spare avaialble if launch fails. Second 10

11. Achieving 1 mm/yr accuracy
Accurate Orbital Models 5 -5
mm/yr
Although much of this is already developed, considerable effort required in making this automatic for sentinel-1
[Could replace the figure with an alternative… colours weren’t clear in your Ashkabad example. Possibly red/green not good here either, but hey)
I propose cutting the slides on atmosphere and orbits all together – leave for questions?
But say “We will produce 1 cm orbits for Sentinel-1, which will effectively eliminate long-wavelength errors from the orbits”
“We will use data from weather models to correct atmospheric path delays – this will remove 50%+ of the noise”
Atmospheric Corrections
Wang, Wright et al, 2008 11

12. Achieving 1 mm/yr accuracy
Error for mission with 12-day repeat
Length scale of observation (km) 5 -5
mm/yr
Duration of time series (years)
Wang, Wright et al, 2008 12

13. Producing High-resolution Velocity and Strain Fields from InSAR and GPS
We have recently developed a method for combining InSAR data from different viewing geometries with GPS to produce continuous velocity and strain fields
The method works by solving for the best-fitting 3D velocities on a pre-defined mesh
Result was noisy, but surprising… strain in strange places. Is this continuous deformation or are there faults there that we didn’t know about?
East Velocity
Strain
Wang & Wright, GRL 2012

14. Identifying previously unknown faults with high-resolution imagery and DEMs
Lepsy fault
SRTM Digital elevation data + N
10 km
Lepsy fault, Kazakhstan
(Walker, Jackson et al, in preparation)
Richard Walker, pers comm
The way you introduced this before was good… one of the reviewers queried whether any faults that remained unknown etc.
I don’t think you need the first slide. Justification is that we recognise hazard associated with faults slipping at < 1mm/yr.
Lepsy fault
10 m
Single event? Length 100 km, slip 10 m .....Magnitude 8.0
17/11/12 14

15. The Team Impact Partners Tectonic Deformation
Wright
Tectonic Deformation
A1: 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 Hazard
B4: 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]
Modelling
C7: 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]
Parsons
Plus 5 PhD students, Partner Nocquet (GPS)
Emphasise world-leading expertise for all the objectives
Barry – the table on page 4 of JoR was supposed to highlight lead of each objective in bold font. Couldn’t see that in the version I have. Can you check leads?
Impact Partners

16. Why us? Why now? Ambitious, Frontier Science Timely Achievable
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.
Finally, I wish to leave you with 4 reasons why this project should be funded….

17. What this project will deliver
Precise Orbits for Sentinel-1
Data
High-resolution deformation measurements from Sentinel-1
Fault Map for Alpine-Himalayan Belt
Water Vapour measurements
Derived products
Earthquake source models
Regional Strain Maps
Earthquake Cycle Deformation Models
3D Models of Continental Tectonics
Models
Earthquake Hazard
Information

19. Q. Management

20. 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)
Need to make assumptions about the size distribution of earthquakes (Gutenberg Richter), and style of faulting, and thickness of seismogenic layer. 20

21. Q. Can we be confident of achieving 1cm orbital precision?
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)
Sentinel-1
Jason-1
JPL/UCL orbit (1cm accuracy)
True trajectory
Biased orbit (mismodelled dynamics)
5cm error

22. Q. How well can we remove atmospheric noise?
Jolivet et al., 2011
We assume, conservatively, that weather models will correct 50% of single interferograms

23. Q. Can we really estimate water vapour in near-real time?
Error on retrieval for an epoch goes as 1/sqrt(N)
For N=15, error in path delay ~ 2 mm; For N=100 (~3 years), error ~1 mm

24. 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

25. Q. Why East Africa? Hammond et al., 2013 Craig, Jackson et al., 2011
Lithospheric thickness
Hammond et al., 2013
Shear-wave anomaly (75 km)
Craig, Jackson et al., 2011
“One of the most exciting developments in the last decade has been the incredible information we are getting from broadband seismology about both the detailed 3D structure of the mantle in deforming zones, and the thickness of the lithosphere itself.
In East Africa, on a large scale, deformation appears to be controlled by variations in lithospheric thickness. Note how the seismicity and faults wrap around this area of thick lithosphere.
On a local scale in Afar, detailed tomographic images from the Afar Rift Consortium, which Tim led, published in geology last week show an intimate relationship between the mantle structure and the surface tectonics. The red zone shows hot, melt-rich region at 75 km depth, directly beneath the surface rift segments.
An unresolved question is the extent to which these deeper structure control the surface deformation, or are completely decoupled, as some suggest. 25

26. Q. How much better than existing missions?
Envisat Data, 70 Day Repeat, 7 years data
40% of areas straining above 10-8 yr-1
Sentinel-1A Data, 12 Day Repeat, 3 years data
80% of areas straining above 10-8 yr-1 [90 % with two satellites]
Wright et al., Fringe 2011

27. Q. How to turn strain into hazard maps?
Need to make assumptions about the size distribution of earthquakes (Gutenberg Richter), and style of faulting, and thickness of seismogenic layer.
Number of earthquakes forecast with M > 5.66, from Bird et al., Green = 1 earthquake per century in a 100 x 100 km area .
[Crude because strain data is low resolution]

28. Q. Time dependent Hazard?
New Zealand Earthquakes
3 September 2010: Darfield, M7.1
21 February 2011: Christchurch, M6.3