Seismologists tracking series of tremors south of Seattle

The Pacific Northwest Seismic Network is sharing an image that shows a series of tremors along the West Coast they've been tracking since April.

"Tremor bursts have continued to excite and confuse all of us tremor watchers over the past month," PNSN Professor Emeritus Steve Malone said in a May 16 blog post.

Seismologists are studying the tremors, with the strongest, according to the blog, south of Olympia and in Oregon and whether they could indicate a “significant slow slip.”

Slow slips are actually fairly common and involve pressure building up in tectonic plates.

The wave of tiny tremors are thought to increase stress on locked faults -- the areas plates cannot move past each other.

However, scientists don't believe the activity is a sign of the "big one."

Slow slips have been shaking the Pacific Northwest about every 14 months or so since at least the 1990s, but blog posts from PNSN say the usual tremor event usually occurs in July or August.

“It is far from obvious that there has been a normal, mostly unilateral progression of tremor up or down the region.  Rather tremor has jumped around with significant batches concentrated in an area for a while and then either moving a bit or dying out,” Malone said in the blog post.