Yes, a M3.5 near South Pasadena and Alhambra. I’m in South Pasadena and it was sharp and shortearthquake.usgs.gov/earthquakes/ev… Focal mechanism shows EW thrust faulting, much like the 1997 Whittier Narrows quake. Today’s quake is west of that event

The M8.2 Alaska quake is on the subduction zone interface. That means the seafloor under the Pacific Ocean is being pushed under the Alaskan peninsula. It also means it generated a tsunami.
earthquake.usgs.gov/earthquakes/ev… @NOAA Tsunami Warning System has issued a tsunami watch for the West Coast. The warning for Hawaii has been cancelled, because the waves are focused east of Hawaii and the event isn't that large. @NWS_NTWC

27 years since the Northridge earthquake. Shaken awake at 4:30, I jumped up to go to work. My 7 yr old panicked - he had learned with the Landers quake that Mommy could be at work for days. So I took him with me & he mapped cracks in the office walls. Now he's in nuclear physics Northridge quake: our old computers couldn't keep up. The algorithm to screen out analog noise bursts in the data misidentified the quake as noise and blocked the data. So much data was coming in from aftershocks, we couldn't get the bandwidth to release the mainshock for 3 hrs

Like #DrBiden, I learned that sometimes you need to add that "Dr.". In the 1980s, I had to dress in shorts and T-shirt to show I was a geologist. Nice clothes at Caltech meant you were a secretary. In the 1990s, all the Caltech/USGS seismologists were on TV explaining earthquakes. The women were called the "earthquake ladies". The men were called seismologists. I started using the Dr. to remind the reporters that women could be scientists too.

We are all dealing with the impact of the Corona virus and I though I’d share how, as a scientist, I think about the risk and my actions in response. First, I try to stay with the data. As data comes in, answers will change. That’s good science. 1/5 2/5 I’m watching the mortality rate - how likely are you to die if you get sick? Flu kills 1 in 1000. Current corona estimate is 1 in 50. This may really be lower because mildly sick people are not being tested. But right now, the rate looks worse than flu.

A tsunami primer (1 of 6):
Tsunamis begin when the shape of the seafloor changes suddenly. The water above the changed seafloor is pushed up, but then because it is a fluid, immediately falls down to both sides, creating the wave that moves towards shore 2 of 6: Tsunamis get taller when they approach shore. The whole column of seawater above a fault is moved, so there is a lot of water & energy in the wave, more if the sea is deeper at the source. As it approaches shore & depth of sea decreases, the height of the wave increases.

Now building codes.
A building is built to withstand some shaking - not some magnitude. Any building can withstand a M8 if it is far enough away.
The code says that a building should not collapse in the worst shaking that has a 10% chance of happening in 50 years. 1/4 There is not one standard for all of California. At every location, @USGS calculates what is the expected shaking from known faults and a new building is built for that. A building in San Bernardino has to be stronger than a building in Orange County. 2/4

I'm seeing lots of confusion between earthquake magnitude, shaking and damage. Here's a simple outline:
Earthquakes happen because of slip across a fault that produces shaking as one of its effects. The total energy released is the magnitude. One number per quake. 1/7 Every point on the quake's fault produces energy, so the bigger the fault, the bigger the quake. Magnitude depends on the fault length, width, and the amount of slip. Both width and slip tend to scale with length, so you can guess the length of the fault from the magnitude. 2/7

Lots of rumors going around about #Kilauea. Scared people make patterns to find safety, but we need to use science to tell us what patterns are real. This thread will have some basic facts about volcanoes. #ScienceForBetterDecisions. 1. Magna with more quartz is stickier, can grow into tall cone, traps gases & more likely to explode: Think Mt. St. Helens or Krakatoa. Low quartz magma, like Kilauea, create lava flows that travel out into a large, flatter shield volcano. Kilauea will not behave like St. Helens!

It seems we need a Calif. geology lesson. The San Andreas is a plate boundary. Everything west of it is moving towards the northwest. Everything east is going southeast. Because the San Andreas is not straight, the plates get crunched. The plates scrunched around the bend in the San Andreas break against each and get pushed up, creating the mountains north of LA and Santa Barbara. Think about how they come down in the rainstorms. Earthquakes are pushing them up faster than erosion is bringing them down.