While the earthquake that struck near Isleton Wednesday morning wasn’t strong, the location did raise questions about the possible risk to an area that is critical to the state’s water supply.  The Delta region in Sacramento County relies on more than 1,000 miles of aging levees to protect local farms and communities that could be vulnerable in a more powerful quake. … At the very center of California’s water system, so much of what we can use comes from or through the Delta. The Delta itself depends on levees to contain the water.  All of that could be compromised if the earthquake is strong enough.

Related articles: 

• San Francisco Chronicle: 4.2 magnitude earthquake near Bay Area, triggering ShakeAlert
• Associated Press: Magnitude 4.2 earthquake shakes part of Northern California, setting off quake alert system