@clive@evan The largest earthquake in the history of Canada had an epicentre near La Malbaie, Québec. That was in 1663, so there weren't many vulnerable buildings around...
Nearly 75% of U.S. could experience damaging #earthquake shaking, recent U.S. Geological Survey-led team of 50+ scientists and engineers. This was one of several key findings from the latest #USGS National Seismic Hazard Model (NSHM). The model was used to create a color-coded map that pinpoints where damaging earthquakes are most likely to occur based on insights from #seismic studies, historical geologic data, and the latest data-collection technologies. https://www.usgs.gov/news/national-news-release/new-usgs-map-shows-where-damaging-earthquakes-are-most-likely-occur-us
Most people have never heard of frost quakes (sometimes called cryoseisms, although this normally refers to cracking of lake and sea ice). New scientific observations suggest that populations in regions prone to frigid winter temperatures will experience them more often. So, now is the time to get up to speed on this icy topic of spooky geology.
Frost quakes are one cause for mysterious booms and shaking heard by northern residents who are not used to earthquakes. They are not uncommon in the upper Midwest and New England, from January to March. Caused by the rapid expansion of water (thermal stress) as it freezes underground, the energy from the expansion releases suddenly, creating a cracking or booming sound, breaking rock layers, fracturing roads, and ripping tree roots.
Frost quakes are more likely to occur where the ground is saturated (after heavy rains or having a high groundwater table) and when rapid freezing occurs – when the temperatures drop to far below freezing over 8 hours.
Frost quake events are very localized and short-lived, however, if the explosive expansion happens near homes or structures, there is the chance that the shaking can cause moderate damage similar to small earthquakes. Frost quakes cannot create shaking and damage to the extent that a geologic quake can, but ground fractures and heaves can damage foundations, land surfaces, and roads. Frost tremors, which have more irregular waveforms, are less violent expressions of the stress release.
Finland seems to be particularly susceptible to frost quakes. In January 2023, the Finnish town of Talvikangas experienced 26 frost quakes in 7 hrs, the greatest number recorded so far. A recent study from Finland will soon be published showing that wetlands, swamps, and irrigated areas, will more likely experience frost quakes.
Frost quakes are typically associated with lack of snow cover. Snow provides some insulation against the rapid freezing that creates the stress leading to the sudden release. Climate change suggests that greater rainfall and less snow will be the trend in northern areas. The reduction in Arctic ice creates a destabilization of the Jetstream that allows frigid air masses to dip south, resulting in the cold zap like we got this month.
As the Finnish study showed, we would be wise to take frost quakes more seriously, as their occurrences may be increasing. Certain structures (utility lines, roads, water towers, power generating facilities, bridges, etc.) should be evaluated for risk from frost quakes even though they are outside typical fault-related seismic risk zones.
Close to a next episode of #EruptionOrNot in #Iceland? Inflation of #Svartsengi is back to pre-dec18th eruption. And now #seismic activity drops. Happens once in a while without following #eruption, the other way around: all eruptions happened after a low in seismic activity...
We were meant to be back working in Iceland from next month, slightly disrupted plans as a colleague who was living in Grindavik is now in the house with her family. Better pack a good tent (for us).
A very cool use for backscatter on a fibre optic link is for #seismic detection, which is currently being used on #Iceland to monitor #earthquake activity.
Outstanding thread on the ongoing #seismic activity in SW #Iceland by @RagnarHeidar but also about the importance of clear mapmaking to help communication.
Our high-level nuclear waste, spent fuel from nuclear reactors, is the most substantive creation of human civilization. It will outlast everything else humans have made.
It is how our descendants will know us, we are the people who made that.
How do we warn the 1,000s of generations who will experience risk from this radioactive waste?
@bojacobs@sts@histodons it is mind-warping to think about how long nuclear #waste lasts, but safe locations with extremely low #seismic activity (like #Finland) can be used to safely store waste for 10s of thousands of years. This, together with how small the waste really is, is enough for me to feel safe knowing that #nuclear is part of the #energy chain.
🇨🇱 #Chile experiences on average two #earthquakes above a magnitude of 1.5 every 24 hours, with a total of 677 in the past year.
One specific challenge is posed by the gaps between the 798 segments that make up the primary mirror 📡. For observing reasons, these gaps must be as small as possible — but the mirrors must still be separated, as any contact between them during an earthquake would be devastating.
In case of an #earthquake, the telescope 🔭 and the dome foundation can slide horizontally on isolators by as much as 30 centimetres 📏 to compensate for the ground movements, minimising shocks to the telescope. https://www.eso.org/public/blog/protecting-elt-from-earthquakes/