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/
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/
12 or so hours after yesterday's M6 Antelope Valley #earthquake, the sequence is on the energetic side, which bumps up chances of more large events: estimated 6% chance of M>6 in the next month, 9% chance of M>6 in the next year 3/
This means that, of past sequences that were like this one statistically, 1 out of 11 of them produced another M6+ quake in the following year. Not expected, but also not that unlikely. The odds of M7+ are much lower, <1% over the next year 4/
Antelope Valley is relatively sparsely populated, but, at a minimum, folks in the immediate area should expect to keep feeling 3s and 4s for a while, and could be hit with something bigger 5/5

• • •

Missing some Tweet in this thread? You can try to force a refresh

Keep Current with Dr. Susan Hough 🦖

Dr. Susan Hough 🦖 Profile picture

Stay in touch and get notified when new unrolls are available from this author!

Read all threads

This Thread may be Removed Anytime!


Twitter may remove this content at anytime! Save it as PDF for later use!

Try unrolling a thread yourself!

how to unroll video
  1. Follow @ThreadReaderApp to mention us!

  2. From a Twitter thread mention us with a keyword "unroll"
@threadreaderapp unroll

Practice here first or read more on our help page!

More from @SeismoSue

29 Jan 20
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.
Never any guarantees in the earthquake business, of course, but the tendency for aftershocks to cluster allows seismologist to make statistical forecasts of both the expected number of aftershocks and their likely spatial distribution.
Read 4 tweets
29 Jan 20
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.
Thing two is that the high tones damp out faster as they move through the crust. If a small quake happens nearby you feel the high tones ("shaking") strongly because they haven't damped out yet.
Read 8 tweets
4 Dec 18
*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.
Fundamentally, moment magnitude reflects the size of the fault patch that moved in an earthquake and the average movement (slip) along that patch. It is not a direct reflection of radiated energy.
Read 11 tweets

Did Thread Reader help you today?

Support us! We are indie developers!

This site is made by just two indie developers on a laptop doing marketing, support and development! Read more about the story.

Become a Premium Member ($3/month or $30/year) and get exclusive features!

Become Premium

Too expensive? Make a small donation by buying us coffee ($5) or help with server cost ($10)

Donate via Paypal Become our Patreon

Thank you for your support!

Follow Us on Twitter!