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This past Sunday morning, a short but strong earthquake gave the Bay Area a rude awakening. Measuring at a magnitude of 3.5, the tremor jiggled San Francisco’s buildings and bookshelves for several seconds at 8:41 a.m.
No damage was reported. But as the San Francisco Fire Department tweeted, the event was “a good reminder we live in Earthquake Country and #Preparedness is key.” As in, pack those go-bags, make sure you’ve got bottled water, and know which table is your sturdiest cover.
But there are only so many ways that San Franciscans can get ready for liquefaction, a terrifying seismic-induced event for which huge swaths of the city are at risk. In liquefaction zones, during the violent shaking of an earthquake (generally with a magnitude of 5.5 or above), “saturated sand and silt take on the characteristics of a liquid,” according to the U.S. Geological Survey. What seemed like solid ground turns into something like gooey cake batter, and buildings and power lines give way in the wake.
In April, the California Geological Survey (CGS) updated its Seismic Hazard Zone map, showing in stark relief which Bay Area communities are most prone to liquefaction and other quake-triggered phenomena, such as landslides. Many well-known SF neighborhoods are at risk, including the Marina, the Financial District, most of SOMA, Treasure Island, and Ocean Beach, as well as chunks of the Mission, the Castro, and the Haight. Virtually the entire shorefront of the East Bay—and two miles inland—is also at risk.
Although most damage in major earthquakes tends to be caused by the earth’s shaking, the potential for destruction is amplified in these areas where the ground can literally turn to mush. And while there are steps that building owners can take to bolster their properties, including foundation retrofits, there are still countless properties around S.F. that don’t conform to the city’s basic seismic codes. Some of the most iconic photos from San Francisco’s 1989 Loma Prieta earthquake, which caused $6 billion in damage, resulted from liquefaction. And California seismologists surmise that the state is long overdue for its next “big one.” “We can expect history to repeat itself in the next big Bay Area earthquake,” writes the U.S. Geological Survey. Let’s hope we’re awake for it.
More earthquake terror: Read the journalist Geoff Manaugh’s article in Wired magazine about the scientists mapping a previously unknown fault system near the Nevada-California border that rivals the San Andreas Fault.
Fire burn and cauldron bubble
The extent of Scotland’s centuries-long actual witch hunt is now on the map, thanks to pioneering students and historians at Edinburgh University. CityLab’s Feargus O’Sullivan reports on the bloody legacy of Scotland’s age of persecution. From the mid-16th to the early 18th century, nearly 4,000 people—the vast majority of them women—were tried for witchcraft, resulting in execution for as many as two-thirds of that number.
The student mapping project brings a wealth of details about the lives of individual victims, which ties into a recent movement in Scotland to grapple with its past and honor the victims, O’Sullivan writes:
Official belief in witchcraft drained away in Scotland in the early 18th century, until the witchcraft acts were repealed in 1735. In recent years, there has been a rediscovery of this bloody history—and a determination to commemorate more fully its victims. The skeleton of Lillias Adie, one of the few accused whose body was not burned after her death in prison in 1704, is due to be returned to a burial site reimagined as a memorial.
There are also plans to reconstruct a historic lighthouse as a national monument to victims of witch persecutions. In the meantime, Scots have use this new map as a way to reckon with this wave of cruelty that happened not just in a vaguely misty faraway time, but in places they know, in some cases just around the corner.
Read ) ♦ LIDAR, but for archaeology: A scholar discovered unknown Mayan ruins using free online digital maps. (New York Times) ♦ Mapping memories: A teenager finds a way to bond with her recently departed mother through a dusty old subway map. (CityLab)
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