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February 19, 2018
78 seconds of Earthquake Early Warning
Late on Friday afternoon, February 16, during the Chinese New Year street fair in la Ciudad de México, the tight hold between the North America and Cocos plates failed, the fault slipped, and the Pacific coast of Oaxaca lurched around a meter out toward the ocean. Within six seconds, the profound ripple this let loose through the crust heaved the Huazolotitlán seismic recording station westward as well, followed shortly by …
April 11, 2017
Who feels earthquakes?
Earthquakes are felt by people somewhere on the globe just about hourly (see this USGS list of felt earthquakes in just the last 24 hours). Some places are particularly prone to them–think Japan, Indonesia, Chile, Italy, California–while some stable parts of the continents will go generations, or even millennia, without anyone there feeling any quaking of the ground. But even in, say, California, where “felt” earthquakes occur daily, most individuals go months …
November 16, 2016
Complex, compound New Zealand earthquake – Part 1: Seismology by Night
Just after midnight last Sunday, the whole country of New Zealand was rocked by a massive earthquake at the north end of the South Island. From the outset, this earthquake was more confounding than most, and as more reports and data amass, we’re gaining a picture of a complicated earthquake that stemmed from the failure of several large faults in succession. These successive failures may have resulted from structural linkages …
September 24, 2015
Chile keeps having earthquakes
…and keeps surviving them barely scathed. Chile has this year been rocked by its 3rd Great earthquake this century–its 14th if you include the last. Though the earthquake’s magnitude and the resulting Pacific-wide tsunami earned it headlines, it was a very mild earthquake in the global scheme of seismic impacts. This has a bit to do with the nature of offshore, subduction zone earthquakes, and a LOT to do with …
May 29, 2015
Views of strong shaking in Nepal and what they teach us
When the ground shook throughout Nepal in April, it was neither predicted nor surprising–the paradox of inevitable but chaotic large earthquakes within well known seismic zones. Though warnings of Nepal’s catasrophic earthquake risk have been sounded for years, and though this magnitude 7.8 and its energetic 7.3 aftershock wrought plenty of death, destruction, and tragedy, scientists are finding themselves somewhat surprised at the apparently rather limited degree of overall damage …
April 17, 2015
Tearing through California Part 1: the Central San Andreas
On display in central and northern California is the rare and troublesome phenomenon that’s the mischievous cousin to sudden, wrenching earthquakes: slow, steady fault creep. Rather than remaining pressed firmly together until they lurch past each other in violent earthquakes, the two sides of a creeping fault glide gradually along, generally silently carrying along everything above them. The good news is that this process takes up strain that would otherwise be …
September 11, 2014
Lurching ground and bouncing bridges in the Napa earthquake
My rides along Amtrak California’s Capitol Corridor now include an eerie stretch where they pass the site at which the highest ground motions in the Napa earthquake were recorded mere weeks ago. Just at the south abutments of the I-80 bridges over the Carquinez Strait, where the Union Pacific tracks pass through the C&H refinery, a shallow borehole seismometer recorded an acceleration of 0.99g, nearly the full force of gravity lurching soil and …
August 30, 2014
Earthquake rupture through a U.S. suburb
In the quiet wee hours of a NorCal summer night, the ground lurched beneath the mud of the northern San Francisco Bay and sent seismic waves roaring upward and outward into the world-famous wine valley’s central city, Napa, CA. After they wreaked their havoc in Napa and nearby communities the seismic waves spread farther afield and gently rumbled most of the Bay Area and its exurbs from our weekend slumber. By the time …
April 2, 2014
Monstrous earthquake in Chile… as it unfolds
The northern coast of Chile has been struck by a Great earthquake this evening, shaking the South America continent for hundreds of miles and thrusting a tsunami onshore and across the Pacific Ocean. Notably, this earthquake occurred in a well known seismic gap, the sole reach of South America’s Pacific coast subduction zone that did not rupture in the 20th (or 21st) century. In that sense, this was one of …
February 18, 2014
How hard has your zip code shaken?
Did you feel it? …Ever? These USGS maps show the highest shaking intensity reported in every zip code throughout the U.S. (and cities of the world) in the past two decades. 1991 – 2012 The USGS’s crowd-sourced Community Internet Intensity Maps, popularly known as “Did-You-Feel-It” maps, have been collecting online surveys of seismic shaking intensity since 1997. There’ve been plenty of quakes in that time, and in 2012 researchers put together …