What do subduction zones do? They do everything! They make earthquakes and volcanos and tsunamis. 😸
When one plate slides under another, it sinks into the hotter parts of the Earth and starts a melting process. The melt floats up creating a line of volcanoes (called a chain or arc) like the Cascades volcanoes in California, Oregon, and Washington. Oceanic-continental converg...Map of Cascades volcanosMount St. Helens (left) and...
The process of sliding one plate under another creates earthquakes. When this happens underwater, if the conditions are right, the vertical motion can spawn a tsunami. Stuck area ruptures, releas...
Not all underwater quakes occur in subduction zones or have the vertical motion to make a tsunami. The Juan de Fuca plate subducts under N. America; but diverges from & slides past the Pacific plate via ridges and transform faults. This motion makes many quakes but not tsunamis. North American plate, Juan ...Catalog seismicity for Juan...
Another important ingredient for making tsunamis: water. A quake on land or one that’s deep down the subduction zone won’t make a tsunami even if it moves vertically. The 1954 Dixie Valley-Fairview Peak, Nevada, earthquakes had lots of vertical motion, but no water so no tsunami. Nevada Earthquake December ...
Learn more about all the things that subduction zones do:
ow.ly/j3XL50BFLbU
ow.ly/tZ4g50BFLbV
ow.ly/3fla50BFLbW
@USGSVolcanoes

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More from @USGS_Quakes

Oct 14, 2021
An intro to earthquake prediction 🧵🧵

Individual earthquakes can’t be usefully predicted. It’s not because they’re mystical or magical. Earthquakes obey very simple physics. The issue is that earthquakes occur deep underground.
In California, earthquakes typically rupture faults at depths of ~10 mi (~15 km). We have no eyes on the fault at depth: can’t see what materials are in the fault, where they’re lubricated by fluids, how close any point is to failure, or how large an area might fail.
If you can’t see the fault at depth, you can’t directly predict what the fault will do. Instead some researchers try to correlate large quakes with other things like having small quakes – or maybe not having small quakes? It’s not clear that there is any predictive power here.
Read 6 tweets
Sep 1, 2021
**New publication alert**
What could happen to communication networks if a large #earthquake happened in the SF Bay Area, along the Hayward fault? 📞📱☎️📳
The new #HayWiredScenario chapter on telecommunications & ICT asks “what if” & explains why we should #TextNotTalk Map depicting SCENARIO distribution of shaking severity in a
Using proxies including power shutoffs, wildfires, & other earthquakes to model what happens to #telecom in a #HayWiredScenario, they found vulnerabilities in power service, cell sites on buildings and poles, and data lines crossing the fault surface rupture. Map of the San Francisco Bay region, California, showing fib
Contributing to the issue are multiple competitive service providers in a largely unregulated industry, convergence of analog and digital systems, layers of hardware and software functionality, dependence on electric power, and the rapid evolution of technology. Photo showing co-located electrical and telecom infrastructuThese photos show repair dependence between telecommunicatio
Read 9 tweets
Jul 9, 2021
Yesterday afternoon, just before 4 pm local time, a M6.0 earthquake occurred at the California-Nevada border. Let’s dive deeper into some of the regional geology on this edition of #FaultFriday.
East of the San Andreas fault, the plate boundary doesn’t stop moving. Even though ~70% of the relative motion of the Pacific-North American plates occurs within the San Andreas fault system, that leaves ~30% to be accommodated elsewhere.
Moving east from the San Andreas fault from ~San Francisco, more plate motion is accommodated at the eastern rangefront of the Sierra Nevada. If you’ve ever wondered why the Sierra look even more impressive from the east than the west, enter: active tectonics.
Read 13 tweets
Jul 9, 2021
Update on the M 6.0 #earthquake that occurred at 3:29 pm Pacific Time July 8, in Antelope Valley, California, near the Nevada border. #califearthquake You can find up-to-date details about the earthquake here: earthquake.usgs.gov/earthquakes/ev…
Shaking of intensities up to VII was reported nearest the epicenter. The quake was felt all the way to the Pacific Coast and throughout CA’s Central Valley as well as strongly in Reno and Carson City.
Did You Feel It? Report here:
earthquake.usgs.gov/earthquakes/ev…
Our @USGS_ShakeAlert earthquake early warning system sent out some ShakeAlert-powered alerts through phone apps and @Google @Android. Check out earthquake.usgs.gov/earthquakes/ev… for more information about ShakeAlert’s performance.
Read 5 tweets
Jul 6, 2021
An M5.2 earthquake occurred 12 km (7.5 mi) NNW of Kukuihaele, Hawaii yesterday at 1:34 PM local time. So far >1,300 people have reported feeling shaking. If you felt this quake (or not!), click the link below to tell us about your experience. For more on EQs in Hawaii, see 🧵👇.
Thousands of earthquakes occur every year in the State of Hawaii most of which are small & caused by eruptive processes w/in the active volcanoes on & around the Island of Hawaii, especially in the southern districts where the Kilauea, Mauna Loa & Loihi volcanoes are most active. Image
Other EQs can occur in Hawaii along tectonic faults in the crust & upper mantle & can be related to deep structural adjustments from the weight of the lava-built islands on Earth's underlying crust. This is the most common source of damaging EQs north of the Island of Hawaii. Image
Read 7 tweets
Mar 4, 2021
Two large earthquakes have occurred beneath the southwest Pacific today. The earlier M7.3 was strongly felt across much of New Zealand. The more recent M7.4 occurred ~4 hr later, ~900 km away. Given the large distance between them, the events are probably not directly related. 🧵 map showing earthquake epicenters for March 5 in the south P
The @USGS-determined focal mechanism and origin location for the earlier M7.3 near New Zealand suggest that the earthquake resulted from complex faulting within the subducting Pacific Plate. earthquake.usgs.gov/earthquakes/ev…
@USGS The M7.4 much farther north along the Kermadec Trench has a focal mechanism and origin depth consistent with slip along the subduction interface between the Pacific and Australia Plates. earthquake.usgs.gov/earthquakes/ev…
Read 5 tweets

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