reinsurance behind the scenes that spreads out the risk worldwide. When an earthquake policy holder makes a claim, their insurers generally recovers 90% of the cost from reinsurers. That's why earthquake instead can have large exposure to San Francisco and not go bankrupt.
It's a proven, reputable market. The loses that occurred when Superstorm Sandy put New York underwater were astronomical. Insurers and reinsurers all held up just fine, though most recorded substantial loses on the year. Houston going underwater was probably even more expensive. An 8.0 Utah earthquake would be small potatoes.