Winthrop Center | 115 Winthrop Square | Financial District

odurandina

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Interesting that the USGS chooses SF as it's poster child;

https://earthquake.usgs.gov/learn/topics/geologicmaps/liquefaction.php

Liquefaction Susceptibility

Liquefaction is a phenomenon where saturated sand and silt take on the characteristics of a liquid during the intense shaking of an earthquake. The highest hazard areas are concentrated in regions of man-made landfill, especially fill that was placed many decades ago in areas that were once submerged bay floor. Such areas along the Bay margins are found in San Francisco, Oakland and Alameda Island, as well as other places around San Francisco Bay. Other potentially hazardous areas include larger stream channels, which produce the loose young soils that are particularly susceptible to liquefaction.

Google Earth File

This layer shows the varying susceptibility in different parts of the region. Susceptibility is delineated in five units from “Very High” to “Very Low” hazard. Roughly one quarter of the San Francisco Bay region may be exposed to liquefaction—the area mapped in the “Very High”, “High” and “Moderate” categories makes up about 25% of the 9-county region.


To follow up on Weigh's post about landfilling: Keep in mind, the USGS makes it sound like man made landfill is the area of greatest concern. But all alluvial sediments of the western Sierra's are highly susceptible. When the Big One hits the LA basin, you may hear about rolling waves and sand geysers.
 

BeeLine

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Semass

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Also some interesting steel laid down on site. Some very large rebar "boxes" too large to fit in one of the slurry rig holes and a number of I beams festooned with bolts.
 

Suffolk 83

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I saw somewhere on FB that the slurry wall is supposed to be finished and they would start excavating in September so we should see more visible phases very soon
 

BeeLine

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Czervik.Construction

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I wish these guys had a Oxblue webcam. These types of projects are fascinating to me to watch and see how they wrestle with mother nature to put up a skyscraper.
 

odurandina

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^^Nice image of old soon to meet new.
i wonder how far they might be along.
 
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meddlepal

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I would like to point out they started significant foundation work for this project around September/October of last year... prep work began Spring of 2018.
 

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