Seismologist, writer, reader, road warrior, grandma. Excited about my new book, THE GREAT QUAKE DEBATE. Tweets are mine mine all mine. #BlackLivesMatter
Jul 9, 2021 • 5 tweets • 2 min read
Did you know that the USGS now issues operational aftershock forecasts for significant events? Start with the event page, e.g., URL below, and scroll down to the aftershock forecast link. These forecasts are based on well-established aftershock stats 1/ earthquake.usgs.gov/earthquakes/ev…
although, like snowflakes, no two aftershock sequences are entirely alike, so forecasts can only give statistical likelihood. Initial forecasts use average parameters for a region, but are updated over time based on how productive a given sequence is 2/
Jan 29, 2020 • 4 tweets • 1 min read
Aftershocks commonly bunch up near the ends of an initial earthquake rupture, in this case suggesting that yesterday's M7.7 broke about 200 km of the plate boundary. Statistically, if another significant quake occurs, it is most likely to be near the most active aftershock zone.
That's what happened in Nepal in 2015: The Dolakha aftershock occurred near where the Gorkha rupture ended to the east, in an area that lit up with aftershocks right after the mainshock.
Jan 29, 2020 • 8 tweets • 2 min read
Let's talk about earthquake shaking. Ppl who feel earthquakes sometimes talk about "rollers" versus "shakers." The shaking you feel in any earthquake depends to some extent on geology: if you live in a valley, you tend to feel waves sloshing, or rolling.
But shaking also depends on earthquake magnitude and distance. Earthquakes release energy with a range of frequencies, like music has a range of tones. The bigger the quake, the stronger the booming low tones. That's thing one.
Dec 4, 2018 • 11 tweets • 2 min read
*THREAD* Okay let's talk about magnitude. For non-specialists, the important point is that magnitude reflects overall earthquake size, whereas the shaking that you feel at any given place depends a lot on what happens to waves after they leave the fault.
The question is, what do we mean by "size." The seismology community has adopted moment magnitude as the "best measure" on an earthquake size; whether we say so or not, we're almost always reporting moment magnitudes, at least for big earthquakes.