Geoscience Reference
In-Depth Information
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-ield
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
1837
17
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 loor 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 8.3
22
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 Paciic
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 7.2
21
or 7.7
22
Simulated for earthquakes as large as
Mw 9.3 to make hazard assessments for
nearby Guam
27
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
