By David Bolling
Given the announced, if fluctuating, 33-percent likelihood of a 6.7 or greater earthquake on the nearby Hayward-Rogers Creek fault between now and 2038, it would seem wise for Sonoma Valley residents to know what to expect and what to do about it.
The Sonoma County Emergency Operations Plan states that, “The Rogers Creek Fault runs directly through the primary urban corridor of the County and poses the greatest risk of surface fault rupture in Sonoma in both likelihood and potential damage.
The level of earthquake damage depends on a variety of factors, including magnitude and duration. The 1989 Loma Prieta temblor had a magnitude of 6.9 and lasted 10 to 15 seconds. The 6.7 magnitude, 1994 Northridge earthquake lasted 10 to 20 seconds, and the great 1906 San Francisco quake had a recalibrated magnitude of 7.9 and has been estimated to have lasted an interminable 45 to 60 seconds.
Among the identified risk factors in Sonoma County are 65 dams, located either in Sonoma County or with inundation areas partially covering Sonoma County. According to the U.S. Army Corps of Engineers, 21 of those dams are of “high or extremely high risk.”
In addition to those dams, explains the County’s Plan, also at risk are two water treatment facilities; 20 wastewater treatment facilities; 1,697 hazardous material sites; four hospitals; 43 fire stations; eight police stations; 206 school buildings – including Altimira Middle School on Arnold Drive; 230 road bridges; three port facilities; and three airports.
Add to that list, “many of Sonoma County’s largest facilities best-equipped for mass care and shelter,” that lie on the Rogers Creek fault.
Sonoma County’s 2023 population was about 482,000. The county’s hazard analysis projects that 398,261 people live in hazard areas, in 152,245 households, of which close to 60 percent are low-income homes.
The impact on all this infrastructure, says the County Plan, includes severe structural damage due to shaking; immediate, simultaneous ignitions caused by the earthquake, including structure and wildland fires.
The County’s planning assumptions also project that “Potable water shortages may occur due to pipeline breaks, loss of storage capacity, loss of power, or compromised water treatment.” That could limit the response available from hospitals, medical care providers, 24-hour care facilities, and the business community. Services also may gradually decline, states the Plan, “due to leaks, or as generators powering pumps run out of fuel or malfunction, and system restoration may take days (for electrical power) or weeks (for water and gas).”
On top of all that, voice and data communication systems may be damaged, overwhelmed or disrupted; major bridges and highways, mass transit rail and bus systems, as well as city streets and roads may all be disrupted, taking weeks or months to repair.
And as previously reported in this space, damage predictions estimate that 11,427 multi-residential units, 3,615 commercial units, and 1,229 industrial units would be moderately damaged to completely destroyed. An estimated 19,372 households would be without water, and about 50,000 households would be without electricity. So what to do?
The Internet is awash with advice for earthquake preparedness. The first line of defense is to be prepared with the immediate necessities required for survival. That means having several gallons of potable water stored at home (at least a gallon-per-person-per day to last a couple of weeks, along with enough non-perishable food to survive that long. You should also have a camp stove and cooking utensils, and adequate fuel; waterproof plastic bags and a few good sized tarps. If you have a gas-powered generator it will be of great value, but you’ll need enough fuel to keep it running. You should also have an abundance of batteries for flashlights and lanterns, back-up power supplies for cell phones, computers, a portable radio, a fire extinguisher and tools to close any gas lines to your house. A well equipped first-aid kit is a must, as is a safe stash of any needed medications.
Earthquakes are always unexpected, even if you’re expecting one. But the California Office of Emergency Services has developed a public, statewide warning system with a free “MyShake” app, available from the Apple Store, Google Play, or at www.earthquake.ca.gov.
In the third part of this report, we will explore strategies for increasing the structural integrity of your home, and examine the cost and benefits of having earthquake insurance.
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