Geodetic evidence for aseismic subduction of the Juan de Fuca Plate

Abstract

A down‐to‐the‐east crustal tilt rate across western Washington disclosed by precise leveling over a 70‐year period suggests that the Juan de Fuca plate is aseismically underthrusting the North American plate. According to this hypothesis, the frequent occurrence of large thrust earthquakes that ordinarily accompany plate convergence need not be expected along the Juan de Fuca subduction zone. This conclusion is consistent with the fact that there have been no great earthquakes in western Washington in historical time (the past 140 years).

Turbidite event history—Methods and implications for Holocene paleoseismicity of the Cascadia subduction zone

“…First thought to be aseismic owing to the lack of historical seismicity, great thickness of subducted sediments, and low uplift rates of marine terraces (Ando and Balazs, 1979;West and McCrumb, 1988), Cascadia is now thought capable of producing great subduction earthquakes on the basis of paleoseismic and tsunami evidence (for example, Atwater, 1987;Atwater and others, 1995;Darienzo and Peterson, 1990;Nelson, A.R., and others, 1995;others, 1996, 2003), geodetic evidence of elastic strain accumulation (for example, Mitchell and others, 1994;Savage and Lisowski, 1991;Hyndman and Wang, 1995;Mazotti and others, 2003;McCaffrey and others, 2000), and comparisons with other subduction zones (for example, Atwater, 1987;Heaton and Kanamori, 1984). Despite the presence of abundant paleoseismic evidence for rapid coastal subsidence and tsunamis, the Cascadia plate boundary remains the quietest of all subduction zones, with only one significant interplate thrust event ever recorded instrumentally (Oppenheimer and others, 1993).…”

Preliminary estimates of recurrence intervals for great earthquakes of the past 3500 years at northeastern Willapa Bay, Washington

“…The net uplift implies that cumulative interseismic uplift has slightly exceeded cumulative coseismic subsidence (Atwater, 1987). However, rates of interseismic uplift at Willapa Bay are poorly known; geodetic estimates for the past 50 years range from near zero (Holdahl and others, 1989;Mitchell and others, 1994) to several millimeters per year (Ando and Balazs, 1979;Hyndman and Wang, 1995).…”

Proceedings of conference XXXIX; directions in paleoseismology

“…3) (Ando and Balazs, 1979;Reilinger and Adams, 1982). By analogy with contemporary deformation in Japan, Ando and Balazs (1979) suggested that tilting in Washington resulted from aseisrnic subduction of the Juan de Fuca plate.…”

“…3) (Ando and Balazs, 1979;Reilinger and Adams, 1982). By analogy with contemporary deformation in Japan, Ando and Balazs (1979) suggested that tilting in Washington resulted from aseisrnic subduction of the Juan de Fuca plate. Reilinger and Adams (1982) and presented evidence that contemporary tilting along the Pacific Northwest coast is accumulating at rates comparable to the long-term averages (~ 10,000 yrs) inferred from tilted 290 marine terraces.…”