A: Melissa from Salinas asked, "do all California beaches have tsunami sirens? If not, why?"
Here's Chief Meteorologist Norm Hoffmann:
There are no California Coastal communities or beaches that have Tsunami warning sirens. A few coastal communities have sirens that could be used for Tsunami warnings, but they are not designated as such. Some communities have partnered with a program the National Weather Service calls "Tsunami Ready." So Coastal communities can receive training and instruction on Tsunamis and put into place emergency evacuation plans and test those plans and be considered a Tsunami Ready Community. You can find information at this location: http://wcatwc.arh.noaa.gov/
As to why they do not have sirens. Around the Pacific there is what is called the "Pacific Ring of Fire" (the graphic I have attached), that goes around the Pacific Ocean. The Pacific Ring of Fire (or sometimes just the Ring of Fire) is an area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean. In a 40,000 km (25,000 mi) horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and/or plate movements. The Ring of Fire has 452 volcanoes and is home to over 75% of the world's active and dormant volcanoes. About 90% of the world's earthquakes and 80% of the world's largest earthquakes occur along the Ring of Fire.
Here on the Central Coast and in most of California, the San Andreas Fault (is part of the Pacific Ring of Fire). On the Central Coast it runs through San Juan Bautista and south to Riverside in Southern California then into Mexico and south America. So most of the major earthquakes occur along that fault line which is inland from the coast. Now there are fault lines all over California, but this is the major fault line on the Pacific Ring of Fire and this is where the major earthquakes (greater than 7.0) can occur. The threat of a 7.0 earthquake or grater occurring off the California Coast is very low, because the main fault line is inland. The concern on the West Coast is off Washington and Oregon where the Major Fault line is 100 to 200 miles offshore.
Geologists are mapping hundreds of faults in California and just along the coast, but the major earthquakes occur on or near the San Andreas Fault and its connecting faults. Tsunami's can occur just off the coast of California, but they are very rare and most earthquakes on these smaller faults would not be large enough to generate a tsunami. Most tsunamis that affect the California Coast occur off the coast of Alaska, China, Japan, southeast Asia or from the Indonesia area and we have 8 to 12 hours to prepare and to evacuate people in coastal areas.
A couple of web sites you might want to check out if you want to keep track of earthquakes in California http://earthquake.usgs.gov/earthquakes/recenteqscanv/ and around the world http://earthquake.usgs.gov/earthquakes/recenteqsww/ .