Source

Tsunamis

Unknowns

Caribbean subduction zone—Faults from oblique convergence between the North America and Caribbean plates near Puerto Rico and the Virgin Islands

A tsunami in 1946, which caused an estimated 1,790 deaths in the Dominican Republic, resulted from a thrust earthquake on or near the plate boundary.14 A tsunami in 1867, with some 30 fatalities in the Virgin Islands, was generated during an earthquake southeast of Puerto Rico in the Anegada Trough (Fig. 3-1b).

What is the tsunami potential of the plate boundary north and northeast of Puerto Rico, and of a probable backthrust south of the island (Muertos Trough)?15 What far-field tsunami hazard does the plate boundary pose to the U.S. Atlantic seaboard?16

Subduction zone off south-central Chile—Source of largest known earthquake, of 1960, and of a predecessor in 183717

The 1837 and 1960 tsunamis each took some 60 lives in Hawaii. The 1960 tsunami also produced strong currents in Los Angeles–Long Beach Harbor. In the source area of the 1960 tsunami, a swath of ocean floor almost 100 km by 800 km probably rose 2 m or more during the 1960 mainshock.18 Tsunamis like the big one in 1960 may have recurred at roughly four-century intervals, on average, during the last 2,000 years (Fig. 3-3b). 19

What factors enabled this subduction zone to produce the outsize earthquake and tsunami of 1960,20 and what do these factors imply for tsunami hazards from subduction zones—including the Kuril, Japan, and Mariana examples below—that are not known to have produced earthquakes of magnitude 9.0 yet may be capable of doing so?21,22

Subduction zone along the Kuril Trench—Produced earthquake of Mw 8.3 in 2006

The tsunami from the 2006 earthquake caused an estimated $700,000 in damage in Crescent City, California.23

How large were the unusually large Kuril earthquakes inferred from geological signs of tsunamis and postseismic uplift in Hokkaido?24,25

Subduction zone along the Japan Trench—No measured earthquake larger than Mw 8.322

In simulations with unit sources having 1 m of seismic slip on fault-rupture patches 50 km by 100 km, Crescent City’s greatest tsunami threat from the western Pacific is the subduction zone along the Japan Trench.23

Is the Japan Trench limited to earthquakes as large as those in its written historical record?26

Mariana subduction zone—No measured earthquake larger than Mw 7.221 or 7.722

Simulated for earthquakes as large as Mw 9.3 to make hazard assessments for nearby Guam27 and distant Pearl Harbor.7

What is the maximum plausible earthquake from the Mariana subduction zone, classically considered a place where plates are weakly coupled and the interplate thrust earthquakes consequently of modest size?28



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