The Forest of Nisene Marks

Well the votes are in and I’m planning on just heading straight on down the list. First up: The Forest of Nisene Marks: better known as that one sinister place that killed 63 people, injured 3700, destroyed dozens of towns, and issued this little critique of 1950s freeway design:  Yup, in the heart of this idyllic woodland likes Loma Prieta, The Dark Hill, where no one knew there was a major earthquake fault until the middle of a SF Giants/Oakland A's World Series Game 3. It was October 17, 1989. It was a 6.9 on the Richter scale, and wikipedia says that it only lasted for 15 seconds, but Joe, who was in Hollister at the time, informs me that the super strong shaking there lasted for over a minute. Before the quake, there had been intense interest in forecasting earthquakes on the San Andreas fault, and the scientists missed this one, though they tried. (it occurred on a ‘previously undiscovered’ fault) Earthquake prediction still remains a very hotly studied, and elusively infuriating science, especially since vulcanologists have gotten their act together so well and are at the academic equivalent of winning 12-0 in the bottom of the 8th. The quake did have two recognized foreshocks though, enough that UC Santa Cruz had sent some instruments up to take more precise recordings on a known ‘dark spot’ on the San Andreas fault. There was even a death in one of the aftershocks, and Wiki’s writeup is one of the worst examples of passive voice in writing that I’ve seen in a while: “one man died when he exited a building through a window and fell five stories” no word whether the victim was one Mr. Wile E. Coyote.    

A couple of interesting phenomena occurred during the quake, 

Liquefaction - soil turned into quicksand. If you shake a jar with big pebbles and little pebbles and sand, things tend to start sorting themselves. A little bit of water in the soil turns into a big puddle of quicksand. Oakland and San Francisco have several areas of city that are built on rocks that were dumped in the bay. The jar was shook. Bad things happened. 

Sand Volcanoes - This is a little water driven geyser of sand that spurts up from the ground as soil is undergoing the liquefaction process. As all the little particles shake down and compact, the water is put under enormous pressure and spurts up and out of the ground, carrying the small particles with it and accelerating the process. Very cool. In SF, these ran so deep that they brought up debris from the 1906 earthquake.  

Landslides - These are pretty self explanatory. 4000 are estimated to have occurred in Nisene Marks Park during the quake. A big one entirely blocked Highway 17 from the Bay Area to Santa Cruz. Took weeks to clear and repair.  

Magnetic Disturbances & Infrasound - Before the earthquake, for 12 days straight, a magnetometer in Corralitos, only a few miles from the epicenter, recorded a substantial increase in super low frequency sound, far lower than even whales and elephants can hear.  This increased abruptly on the day of the quake, peaking at about 3 hours before the quake. Unfortunately for Team Seismologist, this neat little warning has not been repeatable in subsequent earthquake prediction studies and now the data is thought to be due to poor instrument calibration. 

Soft-Story Building Collapse - this is the exceedingly popular building design where there’s apartments/offices up top and shops and lots of glass and things down below instead of a shear wall. These are at a much higher risk of collapse. Not a great idea. Manhattan, think about it. Previously undiscovered fault. Hipster coffee shops. In the 1989 quake, 160,000 apartments were destroyed by this phenomenon.  

Aftershocks - There were 51 subsequent earthquakes with at least a 3.0 magnitude in the following 24 hours. This caused most everyone to not want to be inside. So everyone went camping. On the sidewalk. Including my mother-in-law. Her family coaxed her back inside after a few days.

Your Freeway Was Built By Idiots - Namely, an outfit that went by the name of Grove, Wilson, Shepard and Kruge Contractors, Address 400 Madison Ave. NY, NY, inactive since 1976. It was the only double-decker in California when it opened. In California, space considerations have usually never gotten in the way of a good 14 lane freeway. It was also built on rocks dumped into the bay silt.  This resulted in 42 of the 63 earthquake deaths, as you may imagine from the photographs. The earthquake happened during rush hour too, there were 165,000 cars on this freeway when the quake hit.  Here’s a human interest story to give the flavor of the event: 

Your Bay Bridge Is Like Little Baby - The San Francisco - Oakland Bay bridge has seen a lot of grief in its time. Sailors trying to fly planes. DWA Ships.   No Worries, It Just Scraped the Paint.  Dunno Why But It’s Broken Now.  See We Fixed It With Plan C Anyhow, this double decker bridge also broke during the earthquake, but did the hinge thing rather than the pancake thing. It also popped off a ton of super-important rivets, and we don’t make ‘em like that anymore. The bridge itself moved 7 inches in the quake.  SF and Oakland finally got around to finishing the retrofit in 2013, only 24 years later. I refuse to drive this bridge. There’s lots of perfectly good bridges. More scenic. Other ones.  

Oakland A’s Fans Eternally Disgruntled - To this day, the A’s guys are mad that they lost the 1989 world series, and contend that if only the earthquake hadn’t upset their concentration, the Giants wouldn’t have swept them 4-0. They will talk about this at length. Just bring it up and sit back. It’s better than watching a baseball game. The Giants are immune to earthquake distraction, apparently. One of their many superpowers. 

This week in Chateau Grief, Xander causes an earthquake too.