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Merging geodesy and geology: SCIGN, laser topographic mapping …. … and some aspects of the 1999 Hector Mine earthquake. Ken Hudnut USGS Pasadena, California. CSUN Northridge, California April 23, 2002. The major objectives of the SCIGN array are:.

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ken hudnut usgs pasadena california

Merging geodesy and geology: SCIGN, laser topographic mapping …

… and some aspects of the1999 Hector Mine earthquake

Ken Hudnut

USGS

Pasadena, California

CSUN

Northridge, California

April 23, 2002

the major objectives of the scign array are
The major objectives of theSCIGN array are:
  • To provide regional coverage for estimating earthquake potential throughout Southern California
  • To identify active blind thrust faults and test models of compressional tectonics in the Los Angeles region
  • To measure local variations in strain rate that might reveal the mechanical properties of earthquake faults
  • In the event of an earthquake, to measure permanent crustal deformation not detectable by seismographs, as well as the response of major faults to the regional change in strain
slide5

“SCIGN data quality is excellent – probably the best

of any network in the world…”– Tom Herring, 6/19/01

Scientific Director, UNAVCO

at the 2001 SCIGN Annual Meeting

plate boundary observatory pbo
Plate Boundary Observatory (PBO)
  • Existing sites:
    • PANGA, BARD, EBRY, BARGEN, LVC, SCIGN
  • New sites:
    • Backbone and clusters:
      • Alaska and Cascadia
      • Volcanic complexes
      • San Andreas fault zone
pbo san andreas plan
PBO San Andreas plan
  • Existing sites:
    • BARD, SCIGN, LVC,
    • and BARGEN
  • New sites:
    • Clusters along San Andreas fault, especially along transitions from creeping to locked sections
slide8

High resolution topography along surface rupture of the October 16, 1999 Hector Mine, California Earthquake (Mw7.1) from Airborne Laser Swath Mapping

HUDNUT, K. W., U. S. Geological Survey

BORSA, A., IGPP/SIO, UCSD

GLENNIE, C., Aerotec LLC

MINSTER, J.-B., IGPP/SIO, UCSD

In press, Bulletin of the Seismological Society of America

Special Issue on the Hector Mine earthquake (2002)

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

alsm insar and tm imaging and mapping before after
ALSM, InSAR and TM imagingand mapping before & after

Laser scan of land

surfaces and urban

infrastructure –

buildings & lifelines

- damage assessment

ALSM – 9/11/01 NYC

LANDSAT 7 – earthquake damage - Bhuj, India

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

surface rupture
Surface Rupture
  • Previously mapped, but un-named
  • Lavic Lake fault in recognition of breaks through dry lake bed
  • Up to 5.25 meters of right-lateral motion
  • 48 km overall length of surface rupture
  • Only ruptured once prior through ~50 ka alluvium
hector mine m w 7 1
Hector Mine (Mw7.1)

Photo by Paul ‘Kip’ Otis-Diehl,

USMC, 29 Palms

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).
slide14

R

v

v

r

r

R

Geolocation Vectors and Error Sources

Vector from CMearth to GPS phase center

Magnitude & directional errors both are

stochastic, time and location variant.

Vector from GPS phase center to laser

Magnitude error is constant if no airframe

flexing. Directional error due to constant

and time-varying biases in INS.

Vector from laser to ground footprint

Magnitude error due to timing, instrument

and atmospheric delays. Directional error

from constant mirror mounting offsets and

time-varying biases in reporting of scan

angles (both pitch and roll).

Note: additional errors due to imperfect

synchronization of GPS, INS, mirror scan

and laser firing times must be modeled

and removed as well.

flight plan
Flight 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

slide16

GPS Sites at ≥1Hz During ALSM Mission

Calibration maneuvers at Hector Mine and Lavic Lake

1Hz

2Hz

AGMT

HCMN

NBPS

OPCL

OPCX

OPRD

BMHL

OPBL

OPCP

RDMT

SIBE

TROY

slide19

Southwest Corner of Lavic Lake

dry lake bed for calibrations

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

1999

Hector Mine

earthquake

surface

rupture

  • 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
to assess geodetic capability of repeat pass alsm calibration requirements
To assess geodetic capability of repeat-pass ALSM:calibration 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”).
slide27

Exploded

ordnance

(crater)

Lavic Lake

Roll & Pitch

Maneuvers

pitch maneuvers

slide28

10 cm

vert.

15 cm

vert.

cal val maneuver stacks
Cal/Val Maneuver Stacks
  • Ramp probably due to roll or scan bias
  • End biases are real (low roll/ pitch section)
  • Excellent shot- to-shot varia-bility (5cm rms)
geological quantification and questions
Geological quantification and questions
  • 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 (in press, BSSA)
    • 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
conclusions and some open questions
Conclusions - and some open questions
  • Airborne LIDAR imaging (ALSM) offers remarkable promise for geomorphology, 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 geomorphological 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?