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Restoration Point

This article explores the geological characteristics of Restoration Point in Seattle, focusing on the uplift and basin formation caused by the active Seattle Fault. It discusses the evidence of past seismic events, the identification of active faults, and the uncertainty surrounding the occurrence of devastating crustal quakes.

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Restoration Point

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  1. Restoration Point

  2. Seattle Fault Restoration Point Former sea cliff Present terrace Raised wave-cut terrace

  3. Seattle fault uplift Seattle fault North South erosion Seattle basin N-S contraction drives uplift and basin formation

  4. Seattle fault North erosion South Seattle basin • ~ 6 km subsidence in 15 million years implies about 500 m/million years offset on the Seattle Fault. • If each big earthquake moved the fault 5 m, there must have been 100 events in the last million years. • This implies one event every 10,000 years.

  5. 1998 trenches Mossy Lane Toe Jam Hill fault scarp 1999 trenches 12-ft lidar DEM Restoration Point 1 km

  6. WEST POINT West Point Sewage Treatment Plant construction excavation

  7. “Snags” in Lake Sammamish: 1100 years old

  8. Conclusions • An event that would have had catastrophic consequences occurred about 900 AD. • Individual faults have long recurrence times (1000’s of years). • Many active faults are known and more are being identified. • Jury still out on how often we can expect a devastating crustal quake.

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