Kenneth W. Hudnut U. S. Geological Survey Pasadena, California

Earthquake Hazards SeminarUSGS - Menlo Park, California

May 13, 2003

Measuring Fault Slip -Measuring Fault Slip -Why and How?Why and How?

Measuring fault slip - why and how?Measuring fault slip - why and how? Why?

– What can details of slip variation tell us about earthquake source physics? (You may suggest or prefer other reasons … )

– Variance and other statistical properties of slip distributions - physical relation to fundamental quantities (such as maximum slip, seismic and aseismic energy, stress drop, Dc )

– Large slip variations, if real, could constrain rupture process models and explain high-frequency seismic energy radiation

How?

my bias here is that great earthquakes do differ from small ones– Attempt to observe slip pulses or other crack propagation phenomena

Real-time ‘GPS Fault Slip Sensor’ - to complement inertial sensors

– Variation in slip along-strike and with depth - quantify the errors Airborne Laser Swath Mapping - to observe near-fault deformation

to observe these quantities, need to devise & develop new methods

earthquake earthquake scalingscaling

Are stress drops constant?– e.g., Brune (1970, ‘71)

What about L-model scaling for large events?

– e.g., Scholz (1982, 1994) and Romanowicz (1992)

Bi-linear scaling model– Hanks and Bakun (2002)

Great continental strike-slip earthquakes are of special interest - their slip (and stress drops) may become larger with longer ruptures (up to 10 x W):

– 1857 and 1906 SAF– 1905 Bulnay and 1957

Gobi-Altay– 1920 Haiyun– 1939 Erzincan– Kunlun & Denali

some questions …some questions … How may friction drop co-seismically?

– Opening? What mode of crack propagation?– Key observation - accurate 3D particle motions close to the

fault --- inertial sensors are unable to discriminate between tilt & acceleration; GPS fault slip sensors can help to observe this for future large events

What impedes and stops rupture?– Roughness and variation in slip - heterogeneity of stress, as

well as fault interaction and dynamic effects– Key observation - objective systematic measurements of slip

along-strike at surface for bedrock-on-bedrock fault with large amount of slip; ALSM for Hector Mine

GPS is now vital to earthquake monitoringGPS is now vital to earthquake monitoring(array technology and GPS satellites were(array technology and GPS satellites were

developed in Southern California)developed in Southern California)

GPS is now vital to earthquake monitoringGPS is now vital to earthquake monitoring(array technology and GPS satellites were(array technology and GPS satellites were

developed in Southern California)developed in Southern California)

Measures buildup of strain on faults due to accumulating tectonic motion

Used to detect damage to large engineered structures such as dams, and effects of ground tilt and subsidence on water systems

Can be used in real-time to detect fault slip at surface, for early warning system

Science Review

• List of publications - updates on the main project web page at http://www.scign.org/• 45 papers from 1996 through April 2002 (includes several on Hector Mine co-seismic) -

many important contributions that would have been impossible without SCIGN.• BSSA Hector Mine special issue (May, 2002) contains 16 papers (out of a total of 36)

that made direct or indirect use of SCIGN data. Nearly all 36 then also cited these 16.• Fall AGU 2002 abstracts contain reports on several new projects using SCIGN data in

innovative ways, as well as reports of the new results from the ongoing and coordinated SCIGN Analysis Committee effort, chaired by Nancy King. The use of continuous GPS data for various geophysical and other uses is increasing worldwide, and SCIGN has provided data used in a far wider range of studies than was ever imagined (e.g., Varner and Cannon, 2002). The open data policy has been a key to success.

• SCIGN has become an integral part of what the broader SCEC community does in southern California. These results influence peoples’ thinking well outside of our regional scope, just as we all learn greatly from studies of other regions. Others see the value inherent in having a state-of-the-art array like SCIGN available (hence the PBO part of the EarthScope initiative). New data products are making SCIGN data more easily accessible to a larger and broader base of earthquake and other earth scientists.

1st Year• Combined time

series (1996-2002)

3rd Year• Real-time earth-

quake response

5th Year• Resolve rates on

primary LA basin

faults (and others)

SCIGN Data Products

Photo by Paul ‘Kip’ Otis-Diehl,USMC, 29 Palms

Hector Mine (MHector Mine (Mww7.1)7.1)

Earthquake response rapidly assess the earthquake source

Pacoima Dam GPS structural health monitoring systemPacoima Dam GPS structural health monitoring system (with LA County since Sept. 1995)(with LA County since Sept. 1995)

Pacoima Dam GPS structural health monitoring systemPacoima Dam GPS structural health monitoring system (with LA County since Sept. 1995)(with LA County since Sept. 1995)

Damage estimation rapidly assess damage, casualties, and losses

ShakeMap/HAZUSShakeMap/HAZUS

GPS can help with…GPS can help with… Earthquake response information

– Identify fault source, extent and amount of slip– Model finite fault source– Measure and model deformation field– Provide all of the above to the public, to emergency responders,

and to other scientists

Damage estimation– Provide data for use in HAZUS, etc.– Support of remote sensing and positioning for accurate and timely

collection, reporting and control of other data that require accurate position and/or timing

– Monitor large engineered structures and lifeline systems

Basic positioning infrastructure

Early WarningEarly WarningEarly WarningEarly WarningThe speed of light >> the speed of sound

Seismic

and

GPS

Station

s

CentralComputers Utilities

EmergencyResponse

Transport-ation

(e.g; Wu & Teng, BSSA, 2002; Allen & Kanamori, Science, 2003)

Mitigative ActionsMitigative ActionsMitigative ActionsMitigative Actions

Stop trainsStop nuclear reactionsStop computersSecure hazardous materialsStop elevators

Is 30 seconds of warning enough?

GPS Fault Slip SensorGPS Fault Slip Sensor

K. Hudnut, G. Anderson, A. Aspiotes,N. King, R. Moffitt, & K. Stark

(all at USGS-SCIGN, Pasadena CA)

APEC symposium Proc. Paper, Fall AGU poster,and paper in preparation for

Bulletin of the Seismological Society of America

http://pasadena.wr.usgs.gov/office/hudnut/slipsensor/

what we cannot do…what we cannot do…because the physical process is too chaoticbecause the physical process is too chaotic

weather – weather – turbulenceturbulenceearthquakes - earthquakes - frictionfriction

Recognize a precursor for a particular event

Differentiate readily between the beginning of a M3 and a M7

GPS ‘slip sensor’GPS ‘slip sensor’can help with this!can help with this!

GPS Fault Slip Sensor is proposed to augment Earthquake Early Warning Systems

M3

M7

GPS fault slip sensorGPS fault slip sensor

Real-Time GPS Network - Enhancing SCIGNReal-Time GPS Network - Enhancing SCIGN

On 15 November 2002, first-ever GPS fault slip sensor deployed across San Andreas fault at Gorman, Calif.

Upgrade SCIGN telemetry– DSL, frame relay– Radio repeaters, WiGate and dedicated links– Data buffering

Augment SCIGN real-time acquisition and processing system– Implemented sub-daily processing (4 hr) for ~100 SCIGN

stations (down from 24 hr)– Implementing multiple real-time streaming GPS processors

(commercial software)

Lone Juniper Ranch and Frazier Park High SchoolLone Juniper Ranch and Frazier Park High School

First prototype GPS fault slip sensor

Spans the San Andreas fault near Gorman, California

Initial test results from commercialInitial test results from commercialreal-time GPS processing softwarereal-time GPS processing software

Large data gaps are common

Large and frequent outliers

Require an attentive operator

Do not output real-time resultsnext slideshows this

portion of data

cleaned-up test resultscleaned-up test resultsLJRN position variation

-0.500000

0.000000

0.500000

1.000000

1.500000

2.000000

2.500000

76000 78000 80000 82000 84000 86000 88000 90000

seconds

meters

Why is real-time GPS processing noisy and less robust than post-processing?Ambiguity resolution, multipath, atmosphere and clock errors - what can be done?

precise post-processingprecise post-processing Sub-daily and daily processing runs, e.g.,

with GAMIT/GLOBK, yield absolute station position with sub-centimeter scatter and baseline estimation with few-millimeter horizontal repeatibilities (any size array) and sub-mm/yr velocities

Approaching real-time, GPS is much noisier - inertial sensors are far better

– it can be made to work, “RTK”– many commercial applications

Fundamental limits of GPS– sub-mm phase measurements– 1-second use of precise code ‘narrow-

laning’ for ambiguity resolution

Sub-daily solutions need a bit more work and real-time streaming needs a lot of additional work to be reliable

Upgrading SCIGN telemetryUpgrading SCIGN telemetry

Low cost options such as frequent FTS dial-up, radio nets, and DSLDevelopment & testing of near real-time GPS precise processing, etc.

The Plate Boundary The Plate Boundary ObservatoryObservatory

BARD, mini-PBO & SCIGN are prototype deployments for PBO

PBO will extend the GPS & strain arrays throughout the Western U. S. A. and Alaska

With Canada and Mexico, we hope to cover the North American – Pacific plate boundary

Has been funded($30M for FY03)

Mike Jackson summary:

•~170 new continuous GPS stations

•~60 borehole and 5 laser strainmeters

•Full time staff of six personnel located in Southern CA

•125 SCIGN stations proposed for support under NSF existing networks proposal

•After 5 years SCIGN stations transition to PBO operations and maintenance

SoCal PBO and SCIGN

before moving on …before moving on … State-of-the-art GPS networks and technology development have

become vital infrastructure for earthquake research and response:– Static deformation field data; source models & rapid tilt and strain mapping– Monitoring of large engineered structures (e.g., dams, buildings)– Understanding earthquake source physics - e.g., slip pulses (near-field

accurate particle motions and static displacement field mapping)

New enhancements to telemetry support wider range of applications– Real-time GPS sub-networks of SCIGN

Precise RTK positioning for surveying, AVL and GIS applications– InSAR, Airborne Laser Swath Mapping (ALSM) and digital photography

SCIGN provides ground control for airborne imaging and surveys Mapping and imaging for rapid assessment of damage to buildings, lifeline

infrastructure, etc. (The National Map; Homeland Security)

Collaboration between Scientific, Surveying, GIS, Engineering and Transportation communities has mutual benefits - this is expected to help with funding our projects in the future

ATC-20 building safety inspectionsATC-20 building safety inspections(red, yellow and green tagging)(red, yellow and green tagging)

ATC-20 building safety inspectionsATC-20 building safety inspections(red, yellow and green tagging)(red, yellow and green tagging)

Infrastructure for positioning supports data collection and mapping

during disaster recovery efforts imageryimagerybefore &before &afterafter

Courtesy of City of Glendale

Courtesy of Ron Eguchi

High resolution topography along surface rupture of the High resolution topography along surface rupture of the October 16, 1999 Hector Mine, California Earthquake October 16, 1999 Hector Mine, California Earthquake

(M(Mww7.1) from Airborne Laser Swath Mapping7.1) from Airborne Laser Swath Mapping

Hudnut, K. W. (USGS), A. Borsa (UCSD),C. Glennie (Aerotec, LLC) and J.-B. Minster (UCSD)

Bulletin of the Seismological Society of AmericaSpecial Issue on the Hector Mine earthquake (2002)

http://pasadena.wr.usgs.gov/office/hudnut/docs/

ALSM, InSAR and TM imagingALSM, InSAR and TM imagingand mapping before & afterand mapping before & after

Laser scan of landsurfaces and urbaninfrastructure – buildings & lifelines- damage assessment

Pre- and post-disaster images can be differenced to measure damage and track recovery

LANDSAT 7 & SRTM - damage in Bhuj, India

ALSM – 9/11/01

NYC

USGS:“The

NationalMap”

Active Faults in Southern CaliforniaActive Faults in Southern California

Surface RuptureSurface Rupture

Previously mapped, but un-named

Lavic Lake fault in recognition of breaks through dry lake bed

Up to 5.7 meters of right-lateral motion

48 km overall length of surface rupture

Only ruptured once prior through ~50 ka alluvium

from Treiman et al. (BSSA 2002)

ALSM (Scanning LIDAR imaging)ALSM (Scanning LIDAR imaging)

Slow, precise helicopter flight line data acquisition at 200-300 m AGL.

6888 pps near infra-red (1064 nm) laser.

Scan Width: +/- 20 degrees. Nominally, 180 meters full-width.

200 pulses across swath, ~ 80cm spacing.

Footprint Diameter: Nominally 40cm. Half-meter posting, 15cm horizontal one-sigma

absolute accuracy specified.

Integrated GPS & INS navigation and attitude determination.

Pitch Mirror Correction: maximum +3.5/-6.5 degrees (+ forward bias).

R r

v

Geolocation Vectors and Error Sources

r

Vector from CMearth to GPS phase centerMagnitude & directional errors both arestochastic, time and location variant.

R

vVector from GPS phase center to laserMagnitude error is constant if no airframe flexing. Directional error due to constant and time-varying biases in INS.

Vector from laser to ground footprintMagnitude error due to timing, instrument and atmospheric delays. Directional errorfrom constant mirror mounting offsets and time-varying biases in reporting of scanangles (both pitch and roll).

Note: additional errors due to imperfectsynchronization of GPS, INS, mirror scanand laser firing times must be modeled and removed as well.

Flight PlanFlight Plan

Two overlapping swaths

200-500m mapped width

70 km long

GPS network ≥ 1 Hz

Temporary GPS stations

Cross-swath spurs Roll/Pitch/Yaw calibration maneuvers over dry lake

Flights over well-mapped Hector Mine

GPS Sites at ≥1Hz During ALSM Mission

1Hz 2Hz

BMHLOPBLOPCPRDMTSIBETROY

AGMTHCMNNBPSOPCLOPCXOPRD

Calibration maneuvers at

Hector Mine and Lavic Lake

New methods to explore, new synergies New methods to explore, new synergies between data types (e.g., GPS & ALSM)between data types (e.g., GPS & ALSM)

Combinations of seismic, geologic, and geodetic data in new ways– Source modelling– Hazard modelling

Cross-overs between fields– Geology and

geodesy with InSAR and ALSM

– Seismology and geodesy with high-rate GPS

1999Hector Mineearthquakesurfacerupture

ALSM-Derived Contours of Bullion Mountain Segment

(blue lines are1-foot contours)

To assess geodetic capability of To assess geodetic capability of repeat-pass ALSM:repeat-pass ALSM:

calibration requirementscalibration requirements

Geometry: mount angles, scan offsets, GPS-Laser vector, GPS antenna phase center

Delays: electronic, optical, atmospheric Reference point on laser platform Timing of various components: e.g. INS vs. GPS vs.

mirror attitude sensors Stabilization platforms (delays, accuracy) Detectors (thresholds, amplitude-range “walk”)

Lavic LakeRoll & PitchManeuvers

Explodedordnance(crater)

pitch maneuvers

15 cm vert.

10 cm vert.

Geological quantification and Geological quantification and questionsquestions

Tectonic interpretation of strain release in great earthquakes from their surface rupture– Basic documentation of surface rupture

e.g., Kurushin et al. (1997) study of 1957 Gobi-Altay eq.

How does slip vary along-strike?– e.g., need to assess variance and error in slip rate estimates from

paleoseismic methods e.g., Barka et al. (2002) and Rockwell et al. (2002) extensive studies of

1999 eq.’s in Turkey and similar studies of Hector Mine earthquake (BSSA 2002)

– is high-frequency energy radiated from fault?

Does slip vary from one earthquake to the next?– can detailed topographic mapping of geomorphic features along the

fault be modeled by repeats of exactly the same slip in successive earthquakes, or must slip vary in order to explain the topography?

– slip variation models for earthquake recurrence strongly influence seismic hazard analyses – assumptions made in these analyses necessarily simplify faulting processes, with societal repurcussions

Southwest Corner of Lavic Lakedry lake bed for calibrations

Lavic Lake – compressional stepLavic Lake – compressional step

New methods and data integrationNew methods and data integration

precise topographic mapping of surface ruptures and active fault scarps

representation of actual fault ruptures recorded and preserved in unprecedented detail for use by future earthquake researchers

Airborne platform navigationmust be highly precise andrequires high-rate GPS data

New methods and data integrationNew methods and data integration

Precise topographic mapping of surface ruptures and active fault scarps

– slip models for prehistoric events

– rapid assessment of surface slip and damage patterns after large events

– Requires precise integration of GPS & INS for flight navigation

1957Gobi-Altaiearthquakesurfacerupture

Estimating Estimating slip on slip on

‘max. slip’ ‘max. slip’ segment ofsegment of

the faultthe fault

Estimating Estimating slip on slip on

‘max. slip’ ‘max. slip’ segment ofsegment of

the faultthe fault

Is it a multiple-Is it a multiple-event offset?event offset?

Conclusions - and some open questionsConclusions - and some open questions Airborne LIDAR imaging (ALSM) offers remarkable promise for geomorphology

and fault zone studies, even over inaccessible or vegetated areas Commercial operations are reliable and affordable on well-specified targets with carefully

designed deployments (same as photogrammetry) CAL-VAL maneuvers are essential for geodetic-quality mapping of geomorphic features Turning ALSM into a geodetic-quality tool requires careful calibration and considerable

analysis

– Slip estimation: has been initially developed demonstrated new and improved methods are being developed systematic measurement along the surface rupture will be done and then

compared with geologic estimates, InSAR and other methods quantitative assessment of slip variation along-strike

– dynamic faulting models – is high-frequency energy radiating from the fault?

– Quantitative geomorphology Model tectonic landform evolution

– Did topographic features form as a result of exactly repeated slip distributions?– Can topography be explained by only certain combinations of slip in past events?

Demonstrated GPS application to augment earthquake early warning systems

– Understanding earthquake source physics - e.g., slip pulses & rupture mechanics Near-field accurate 3D particle motions and static displacement field estimation Making real-time GPS into a precise, reliable system requires considerable development work