For California, another large earthquake is inevitable. In 1906, a magnitude 7.9 earthquake struck San Francisco and destroyed 28,000 structures, over 80% of the city’s buildings at the time. The magnitude 6.9 Loma Prieta earthquake in 1989 is estimated to have caused anywhere from $6-10 billion in property damages around the Bay Area. But these days there’s technology to help buildings resist earthquakes. One the most robust ways for a building to resist earthquake damage is base isolation. As a follow-up to the detailed New York Times article about base isolation, we take a deep dive into base isolation in San Francisco.
Whoa, was that an earthquake last night? Did you check out Nextdoor or Twitter to see if others also woke up? It’s actually good news when earthquakes hit at night instead of during the day. Night earthquakes mean fewer injuries and fewer fatalities. Let’s look into why this is the case.
So far in this series, we’ve covered proximity to fault lines in part one and soil liquefaction and landslides in part two. Another area to look into before buying a house in earthquake country is proximity to dams. Their watersheds cover vast areas, causing massive flooding downstream if the dam fails during an earthquake.
When an earthquake strikes, the intensity of earthquake shaking determines the severity of damage. In turn, the main factors affecting earthquake shaking intensity are earthquake depth, proximity to the fault, the underlying soil, and building characteristics—particularly height. Let’s take a look at the latter two (soil and buildings) and how they interact.
Recent natural disasters such as the California fires and Hurricane Michael suggest that we’re living in an increasingly precarious world. However, are earthquakes also increasing in frequency?