Google runs a company-wide disaster recovery testing event every year. Earthquakes are among the numerous scenarios simulated.
http://craphound.com/overclocked/Cory_Doctorow_-_Overclocked...
Now, there may certainly be larger systemic effects over long time periods caused by eg. the death of the company CEO, the loss of new product development, or the complete destruction of the company's market (in, for example, a global thermonuclear apocalypse that sets us back to the stone age). But the tests absolutely do simulate the simultaneous death of 15,000+ employees, destruction of the Mountain View headquarters, and loss of all datacenters, data, and power in the Bay Area, and verify that remote teams can continue the day-to-day operations in such an event.
On the scale of devastation this article is describing, none of Google's servicing being obliterated really matters but I'm personally pretty glad Google is prepared for multiple, massive scale disasters to happen at once.
When the towers went down in 2001, the first business priority of many companies was getting email back online. It's an incredibly important part of a business.
The search engine that holds the vast majority of the worlds traffic? The search engine that everyone is going to call on minutes after the earthquake to get news, but isn't going to be there so all the other search engines slow to a crawl. If Google search just disappeared for a week there would be a considerable number of businesses go out of business. You see it now in one off cases where a site is delisted and its traffic drops 99%.
That said, Google has datacenters around the nation and the world so that scenario is unlikely.
The one thing you should bear in mind about earthquakes is that in many cases the aftershocks make more damage than the main one, because damage accumulates. Which means that critical infrastructure could take weeks to become fully operational.
Perhaps you can, but how many companies are now wholly dependent on Google for their groupware functionality? What happens if you're one of the gaggle of people who make a living off YouTube?
I bet Google could absorb 100% of the emergency evacuation of AWS in a pinch. Remember also that not 100% of services will be moved, and those that are will not be running at 100% capacity - everyone would be suspending their batch/analytics/warehousing jobs that week (or month).
EDIT: Also, lock in would stop all the redshift/dynamo/etc users from migrating, and would limit people to just what they could throw up on GCE/GAE.
There were Wall St firms that literally had to get the military to escort them into Lower Manhattan in the days after to rescue servers, tapes, etc and cobble something together in a satellite office.
No one wants a repeat of that, and you'll notice subsequent disasters like Sandy have barely been a blip for most as a result of policy changes.
At this point basically any major company will/should have procedures in place for "perfect" DR, the ability for everyone to work from home indefinitely (and alternate offices/infrastructure waiting for the few people who need something special, like the special needs of a trading desk), as well as obviously having back up data centers with full replication.