Abstract

Coseismic vertical displacements and interevent uplift rates associated with 12 episodic tremor and slip events on the Cascadia subduction zone occurring between 1996 and 2011 have been determined from hourly water level records from four National Oceanic and Atmospheric Administration (NOAA) tide gauges (Neah Bay, Port Angeles, Port Townsend, and Seattle). Whereas vertical displacements during individual events are on the order of millimeters with centimeter uncertainties, 12‐event average displacements by site are resolved to a few millimeters (1.35±1.50  mm at Neah Bay, 3.86±1.29  mm at Port Angeles, 2.38±1.22  mm at Port Townsend, and 0.13±1.78  mm at Seattle), which agree with displacements inferred from modeling Global Positioning System (GPS) data. Examination of water levels between events shows an interseismic deformation rate approximately equal in magnitude but opposite sign (but with higher uncertainties) with episodic tremor and slip events, on average, releasing strain accumulated between events. Analysis of pre‐GPS (1980–1995) water levels suggests that the time interval or average displacement pattern has changed between 1980 and 2011.

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