On October 18, millions of Californians will “drop, cover and hold on” for the “Great ShakeOut” earthquake drill, an annual event that puts earthquake preparedness and safety to practice.
More than 58 million people from across the globe registered to participate in the drill this year, and it’s likely no surprise that a large portion of those who signed up—almost 10 million—were from California.
California has a long history of catastrophic quakes, and reports over the years have suggested that the state is long overdue for the next “big one.” In fact, data from U.S. Geological Survey (USGS) geophysicists shows the probability of a big quake hitting California is only a matter of time:
Probability of an Earthquake hitting the Los Angeles region in the next 30 years
- Earthquake measuring magnitude 6.7—60 percent
- Earthquake measuring magnitude 7—46 percent
- Earthquake measuring magnitude 7.5—31 percent
Probability of an Earthquake hitting the San Francisco Bay in the next 30 years
- Earthquake measuring magnitude 6.7—72 percent
- Earthquake measuring magnitude 7—51 percent
- Earthquake measuring magnitude 7.5—20 percent
(Data source: 2014)
A Measure of Magnitude and Intensity
To get a better sense of the data above, it’s important to define both magnitude and intensity as they pertain to earthquakes.
Magnitude is the measurement of energy released at the source of an earthquake. This is the graphical data that shows up on seismographs. Intensity is the measurement of the strength of the earthquake’s shaking at a given point—it’s determined by examining people, structures and the surrounding environment.
The USGS uses the Modified Mercalli Intensity Scale to give a better sense of the comparison between magnitude and intensity:
Modified Mercalli Intensity
|1.0 – 3.0||I|
|3.0 – 3.9||II – III|
|4.0 – 4.9||IV – V|
|5.0 – 5.9||VI – VII|
|6.0 – 6.9||VII – IX|
|7.0 and higher||VIII or higher|
Typical Maximum Modified Mercalli Intensity:
I – Not felt except by a very few persons under especially favorable circumstances.
II – Felt only by a few persons at, rest, especially on upper floors of buildings, Delicately suspended objects may swing.
III – Felt quite noticeably indoors, especially on upper floors, but many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibration like passing truck.
IV – During the day, felt in doors by many, outdoors by few. At night, some awakened, Dishes, windows, doors disturbed; walls make creaking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.
V – Felt by nearly everyone; many awakened. Some dishes, windows, etc., broken; a few instances of cracked plaster; unstable objects overturned. Disturbances of trees, poles, and other tall objects sometimes noticed. Pendulum clocks may stop.
VI – Felt by all, many frightened and run outdoors. Some heavy furniture moved; a few instances of fallen plaster or damaged chimneys, Damage slight.
VII – Everybody runs outdoors. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable in, poorly built or badly designed structures; some chimneys broken. Noticed by.persons driving cars.
VIII – Damage slight in specially designed structures; considerable in ordinary substantial buildings, with partial collapse; great in poorly built structures. Panel walls thrown out of frame structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned. Sand and mud ejected in small amounts. Changes in well-water levels. Disturbs persons driving motor cars.
IX – Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb; damage great in substantial buildings, with partial collapse. Buildings shifted off foundations. Ground cracked conspicuously. Underground pipes broken.
X – Some well built wooden structures destroyed; most masonry and frame structures destroyed with foundations; ground badly cracked. Rails bent. Landslides considerable from river banks and steep slopes. Shifted sand and mud. Water splashed over banks.
XI – Few, if any, masonry structures remain standing. Bridges destroyed. Broad fissures in ground. Underground pipelines completely out of service. Earth slumps and land slips in soft ground. Rails bent greatly.
XII – Damage total. Waves seen on ground surfaces. Lines of sight and level distorted. Objects thrown upward into the air.
When the Quake Hits
While it’s important to consider the potential for destruction and devastation, the real goal of the Great ShakeOut—and earthquake preparedness in general—is to focus on proactive and preventative measures that will increase resiliency and safety when the next big quake hits.
Trying to pinpoint when the next big one will hit is impossible. That’s why it’s important to examine the surroundings and environments you frequent and prepare accordingly.
As highlighted on the Great ShakeOut’s website, federal, state and local emergency management experts and preparedness organizations agree that “drop, cover, and hold on” greatly helps reduce injury and death during earthquakes.
Drop, Cover and Hold On
- Drop where you are, onto your hands and knees. This position protects you from being knocked down and also allows you to stay low and crawl to shelter if nearby.
- Cover your head and neck with one arm and hand
- If a sturdy table or desk is nearby, crawl underneath it for shelter
- If no shelter is nearby, crawl next to an interior wall (away from windows)
- Stay on your knees; bend over to protect vital organs
- Hold On until shaking stops
- Under shelter: hold on to it with one hand; be ready to move with your shelter if it shifts
- No shelter: hold on to your head and neck with both arms and hands.
The primary goal of “drop, cover, and hold on” is to immediately protect yourself as best as possible wherever you may be located. In more extreme earthquakes, the shaking experienced will be so violent that you may not be able to run, walk or even crawl. Additionally, these sudden and intense jerking motions (several feet per second) will create a number of dangerous situations, including unsecured objects toppling, falling or becoming airborne.
As such, it’s recommended that during an earthquake you:
- Avoid Doorways: In modern homes and buildings, doorways are no safer than any other area and do nothing to protect you from flying or falling objects—stick with staying under a table.
- Do Not Run Outside: In the midst of an earthquake, there is great potential to be seriously injured or killed by falling or flying objects and debris. Again, secure a safe location under a table or similar stationary object that will protect you.
Before the Next Earthquake Hits
The following steps provided by the Great ShakeOut offer a basic set of recommended actions for preparing your home or workplace environment for an earthquake:
- Step 1: Secure your space by identifying hazards and securing movable items.
- Step 2: Plan to be safe by creating a disaster plan and deciding how you will communicate in an emergency.
- Step 3: Organize disaster supplies in convenient locations.
- Step 4: Minimize financial hardship by organizing important documents, strengthening your property, and considering insurance.
Beyond these measures, there are a number of available resources that can help your organization or home better prepare for the next big earthquake, including drills, checklists and educational resources provided by the Great ShakeOut on a range of topics:
- For Businesses
- For Nonprofits and Other Organizations
- Earthquake Safety in Stores
- K-12 Schools
- Government Agencies and Facilities
- Healthcare Organizations
- For Parents and Care Providers of Young Children and Infants
- Seniors and People with Disabilities
Should you need additional resources or have questions pertaining to your organization’s earthquake preparedness program, please don’t hesitate to contact our team.