Work at the #PebbleHill #reservoir began in the fall of 2021 to prepare for #NaturalDisasters in the future.
Metro #Vancouver has been steadily #upgrading its reservoirs since the '90s to ensure it can provide #water to the region following the "#BigOne " — a #megathrust #earthquake expected to hit the #BCcoast someday.
https://www.cbc.ca/amp/1.6783105

#BritishColumbia #Canada #PNW #PacificNorthwest #EarthquakeProofing #PlanningAhead #Cascadia #YVR

I am totally astounded by what I read when I compare these two texts: Maria Graham's description of the coastal #uplift due to the 1822 #Valparaiso #earthquake, versus Charles Darwin's text on very similar phenomena related to the 1835 #Concepción earthquake.

Read carefully, paying attention to the expressions used. It's like if #Darwin borrowed Maria Graham's words, but also her interpretation about the accumulation of earthquakes raising the coast on the long term. 🤔
Any comment ?

Both 1822 and 1835 earthquakes happened in Central #Chile on the #subduction #megathrust between Nazca and South America #tectonic_plates. Darwin's description, based on Fitz Roy (Beagle's captain) observations, is considered as seminal.

Thanks @haq for pointing me to the work by Maria Graham.

This recalls that even in contexts like #Java or #Sumatra, where the #subduction #megathrust may produce very big #earthquakes, much smaller shallow crustal ruptures may present significant hazards because closer to towns.
2/2

Today’s M6.9 shallow #megathrust #earthquake (approximate location as purple blob) in the context of the #rupture areas of (numerous) previous #subduction events near #Sumatra on a map from Putra et al. (2016)

A magnitude Mw6.9 #earthquake offshore south-central #Sumatra.

Mechanism and location suggest rupture on the shallow part of the #subduction #megathrust close to the trench (on the very shallow dipping fault plane). However, modelled depth of ~19km, if true, seems little too deep given the closeness with the trench (USGS gives same depth and mechanism). This means that we cannot exclude a rupture on the steep fault plane within the oceanic plate.

Map with source time function from Geoscope IPGP
http://geoscope.ipgp.fr/index.php/en/catalog/earthquake-description?seis=us7000iqpn
Larger map with epicenter of this event in red from USGS (both not yet on fediverse it seems)