Tremor

Slow Slip episodes affecting southern British Columbia and northern Washington have been occurring every 14 months or so since at least the 1990s. The PNSN monitors the non-volcanic tremor associated with slow slip and has deployed additional seismometers from time to time to record expected tremor events to gain insight into the process and into the stresses that eventually will lead to the region's next major earthquake.

Many different techniques are used to study this phenomenon. The two primary areas of research the PNSN and related researchers are involved in include; 1. A semi-automatic tremor detection and location process that uses continuous waveform data from the PNSN and cooperating networks and has a web interface called, Interactive Tremor Map; 2. Experimental algorithms applied to waveform data from special installed small aperture arrays to better characterize the space and time distribution of tremor. The last detailed experiment was back in 2009 - 2011 called an Array of Arrays.

Episodic Tremor and Slip (ETS) periods in northern Washington have been individually studied over a number of years. During each of these periods web pages were constructed at the time describing the events and the research efforts made to study them.  Here we list references to the original pages as then constructed.

We have made some comparative tremor map snapshots showing tremor locations by week of several previous northern Washington ETS events.  There is also a set of comparative density maps for the past three ETS episodes.