Last night's explosion of a PG&E natural gas line in San Bruno was a horrifying experience. One can't imagine what that must be like to lose your home, possessions, memories, and potentially even family in a heartbeat.

In addition to the sad news from San Bruno, this morning, there was news of minor explosion in a PG&E vault in San Francisco.

Another one?

Let's take a stroll through recent history of vault explosions in San Francisco.

Vault fire at Polk and O'Farrell in June 2009

Aug 2005 - Vault explosion at Post and Kearny Jun 2008 - Underground explosion shakes SF Financial District Jun 2009 - Underground explosion at Polk and O'Farrell Jul 2009 - Underground explosion at 4th and Market Jan 2010 - Underground vault fire at Geary and Jones Jun 2010 - Vault explosion in Pac Heights Sep 2010 - Vault fire at Sutter and MontgomeryMar 2011 - Underground Explosion Closes Post And Grant

After the explosion in 2005, PG&E decided to check all 550 underground vaults in San Francisco. Check out this article from the SF Chronicle. Sounds like they did a great job.

Pacific Gas and Electric Co. will begin inspecting about 550 underground electric vaults in San Francisco today following a power transformer explosion last week that critically injured a woman. According to company officials, the inspection is expected to take five weeks and will focus first on 150 transformers that have not been inspected this year. An explosion in an underground vault at Post and Kearny streets Friday shot a tower of flame into the air, blowing a manhole cover 30 feet, burning a pedestrian and setting the awnings of the Polo Ralph Lauren store on fire.