Finding faults with LIDAR in the Puget Lowland

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Finding faults with LIDAR in the Puget Lowland

• Ralph Haugerud, Craig Weaver
• U. S. Geological Survey
• Jerry Harless
• Puget Sound Regional Council
• and thanks to TerraPoint LLC, Houston TX

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• Why LIDAR?
• What is LIDAR?
• How are we doing LIDAR?
• What are we finding?

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In some places, it is easy to see where the
active faults are.
30 km
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In other places, it is not.
Seattle
Tacoma
30 km
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What are the salient differences?
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age ? slip rate feature size

• 18,000 yr ? 1 mm/yr 18 m
• 106 yr ? 1 mm/yr 1 km
• In the Puget Lowland, to see a fault with the
  same slip rate as in the SF Bay area, we have to
  look more closely.

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LIght Detection And Ranging

• Airborne scanning laser rangefinder
• Differential GPS
• Inertial Navigation System
• 30,000 points per second at 15 cm accuracy
• 4001000/mi2, 106 points/mi2, or
  0.040.1 cents/point
• Extensive filtering to remove tree canopy
  (virtual defor-estation)

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10-meter DEM from contours
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12-ft DEM from LIDAR
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Picture Oblique view of S end Rockaway Beach
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High-resolution LIDAR topography
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• Fly in winter, when leaves are off
• Near-infrared laser doesnt penetrate clouds,
  rain
• Errors
• Largest are in anglesup to 1 m x-y error
• Ranging error 15 cm z error!
• 2/3 of surveyed points on trees and buildings
  remove with automatic geometric filtering
• Multiple reflections from one laser pulse
  better filtering

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• Optimum working distance circa 1 km
• Adequate reflection brightness
• Keep laser eye-safe
• Spot diameter decimeters to meters
• Spot spacing 1 to 5 meters
• Multiple passes
• multiple look angles
• higher point density
• internal consistency check
• 400 - 1,000 / mi2

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Why is LIDAR better than photogrammetry?(Its
the trees)
Suppose timber allows 1 of 3 arbitrary rays to
reach ground 1/3 of ground can be surveyed by
LIDAR
Photogrammetry requires 2 separate views of a
point only 1/9 of ground will be locatable
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Bainbridge Island,KPUD1996-1997
Seattle
Snoqualmie, USGS-NMD 1998-2001?
Tacoma
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Puget Sound LIDAR Consortium
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Puget Sound LIDAR Consortium

• No formal structure
• One agenda
• One contract
• Separate payments
• Share data
• Release all data to public domain
  (www.GetItYourselfBob, to be hosted by UW
  library)

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PSLC

• Seattle

Tacoma
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3M
LIDAR already flown
Seattle
to be flown this Winter
Tacoma
3.3M
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15 km west of Seattle
Toe Jam Hill fault scarp
Waterman Point scarp
beach uplifted during 900 AD earthquake
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• landslides

southern Bainbridge Island
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Uses for high-resolution topography

• Finding faults (earthquake frequency, kinematics)
• Geologic mapping
• Landslide hazards
• Flood hazards, groundwater infiltration, runoff
  modelling
• Fish habitat
• Precision forestry
• Noise propagation