Could Los Angeles withstand a ‘megaquake’? A Public Adjuster’s take on Earthquake Preparedness.

Posted on Dec 14, 2013 by Pride Public Adjusters

 

As cities grow and technology evolves, the increasing level of complexity enhances vulnerability to earthquakes.

It’s not a question of if the San Andreas fault ruptures in Southern California, but when.

This was the message of US Geological Survey (USGS) scientist Dr Lucy Jones here at the American Geophysical Union meeting in San Francisco.

 

Giving a public lecture at

thegathering of more than 20,000 geoscientists from across the globe, Dr Jones outlined

the dangers and challenges Southern California faces as it waits for the next “big one”.

The region accommodates the major urban centres of Los Angeles and San Diego.

 At the time of the infamous earthquake that hit San Francisco in 1906, less than one in three US citizens lived in cities, but now the overwhelming majority of the American population is urban, and urban resilience is a big issue.

Much of the current focus on earthquake planning is acted out in building regulations. Californian construction codes are based on satisfying a target of 90% probability that a building does not collapse.

In other words, there is a tacit acceptance that 10% of buildings could collapse in the vicinity of the next maximum credible earthquake. Such earthquakes hit California once every three centuries or so.

In addition, in the event of such a quake, some buildings that do not collapse will nonetheless remain uninhabitable, due to the risk of collapse in aftershocks. These are given a so-called “red tag”.

Past experience shows that this is a significant multiplier. In the magnitude 6.7 earthquake that hit Northridge, 20 miles north-west of Los Angeles in 1994, around 230 buildings collapsed but around 2,300 red tags were issued.

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