A recent article in the New York Times "San Francisco's Big Seismic Gamble" sheds light on the uncertainties associated with the performance of high-rise buildings in San Francisco during earthquake ground shaking.
It reminded me of the magnitude 6.1 earthquake in Christchurch, New Zealand, in 2011. This earthquake showed that in a country with a proud tradition of earthquake resistant design and stringent building codes, even a moderate earthquake can lead to very large economic losses of USD 23.8 billion, if the quake hits a city unfortunately. This also means that not just extreme scenarios can generate large consequences in San Francisco, because earthquakes do not read codes, whose primary aim is to save lives.
The New Zealand earthquake also showed that most pile foundations in soft soil performed as anticipated by their engineers; however, some buildings, which were resting on piles experienced large building damages. How the San Francisco's Leaning Millennium Tower, which like many San Franciscan skyscrapers is founded on liquefiable soil, will perform during the next quake remains to be seen.
Nevertheless, if a skyscraper in downtown San Francisco will be classified as unsafe to use, then also neighbouring buildings can be cordoned off as observed in Christchurch's Central Business District, thus impacting the continued business operations for businesses with tens of thousands employees. Building owners and tenants and the public at large are in general not aware of the complex damages that earthquakes can generate and additional complicated follow-up consequences.
Finally, the public in New Zealand caught by surprise and had a different opinion on how earthquake resistant building would perform. Hence, the New York Times article is a relevant brick in the communication of seismic risk to the public and it tells it as it is. It makes people aware of the potential consequences and thereby allows the reader to be better prepared, when the next one will strike.
PS: "Earthquake do not read codes" is a quote by famed earthquake engineer Thomas Paulay (1923-2009)
Category: Climate/natural disasters: Earthquakes
Location: San Francisco, CA, USA