Health & Safety

May 10, 2013

Preparing to survive: Shaky facts

There is a tendency to think that earthquakes are confined to California and the west coast. In fact, the earth has “moved” for a very long time. The earliest incomplete recorded evidence of an earthquake was traced back to 1831 B.C., in the Shandong province of China. However, there is a complete record starting in 780 B.C., during the Zhou Dynasty in China. While we may not be able to predict when a major tremor will occur, acquiring some basic knowledge and staying informed will allow us to make better decisions regarding our preparation and recovery processes.

 

Let’s examine some basic tenets we know to be true regarding earthquakes:

 

• The largest recorded earthquake in the U.S. was a magnitude 9.2 that struck Prince William Sound, Alaska, March 28, 1964, Coordinated Universal Time.

• The largest recorded earthquake in the world was a magnitude 9.5 in Chile, May 22, 1960.

• The earliest reported earthquake in California was recorded in 1769.

• The average rate of motion across the San Andreas Fault Zone during the past 3 million years was 56 millimeters per year (2 inches). This is about the same rate at which your fingernails grow. Assuming this rate continues, scientists’ predict that Los Angeles and San Francisco will be adjacent to one another in approximately 15 million years.

• The first “pendulum seism scope,” used to measure the shaking of the ground during an earthquake, was developed in 1751.

• Moonquakes (earthquakes on the moon) occur, but they happen less frequently and have smaller magnitudes than earthquakes on earth. It appears they are a result of the tidal stresses associated with the varying distance between the earth and moon. They also occur at great depth, about halfway between the surface and the center of the moon.

• Although both are sea waves, a tsunami and a tidal wave are two different unrelated phenomenon. A tidal wave is a shallow water wave caused by the gravitational interactions between the sun, moon and earth. A tsunami is a sea wave caused by an underwater earthquake or landslide, displacing ocean water.

• The hypocenter of an earthquake is the location beneath the earth’s surface where the rupture of the fault begins. The epicenter of an earthquake is the location directly above the hypocenter on the surface of the earth.

• Each year southern California has about 10,000 earthquakes. Most of them are too small to feel. Several hundred are greater than magnitude 3.0 and roughly, 15 to 20 are greater than magnitude 4.0. If a large-scale earthquake occurs, the aftershock sequence will produce many more earthquakes of all magnitudes for many months.

• The magnitude of an earthquake is a measured value of the earthquake size. The measured magnitude is the same, no matter where you are, or how strong or weak the shaking is in various locations. The intensity of an earthquake is a measure of the shaking created by the earthquake and its value does vary with location.

• There is no such term as earthquake weather. Statistically, there is an equal distribution of earthquakes in cold weather, hot weather, rainy weather, etc. Furthermore, there is no physical way that the weather can affect disruptions several miles beneath the surface of the earth. The changes in barometric pressure in the atmosphere are very small compared to the forces in the crust and the effect of the barometric pressure does not reach beneath the soil.

Most earthquakes occur at depths of less than 80 kilometers, or 50-miles from the earth’s surface.

• The San Andreas Fault is NOT a single, continuous fault, but rather a fault zone made up of many segments. Movement may occur along any of the many fault segments along the zone. The San Andreas Fault system is more than 1300 km (800 miles) long and in some spots is as much as 16 km (10 miles) deep.

• Alaska is the most earthquake-prone state and one of the most seismically active regions in the world. On average, Alaska experiences a magnitude 7.0 earthquake every year and a magnitude 8.0 or greater earthquake every 14-years.

• The majority of the earthquakes and volcanic eruptions occur along plate boundaries such as the boundary between the Pacific Plate and the North American plate. One of the most active plate boundaries where earthquakes and eruptions are frequent, is around the massive Pacific Plate commonly referred to as the Pacific Ring of Fire.

 

The facts depicted barely scratch the surface, but the data does represent accurate information and historical perspective. The earth will continue to move as it always has because global shaping is an incessantly dynamic process. Geologists, seismologists, plate tectonics experts and physicists will continue to strive for more information and ultimately be able to answer the most elusive of truth-predictions.

To reiterate the reality theme again, you do live and work in earthquake country. Acquiring knowledge about this phenomenon can only enhance your chances of being better prepared.

Visit the Federal Emergency Management Agency website at www.fema.gov or the United States Geological Survey at www.usgs.gov websites for more information.

It comes down to one simple fact: it is not if a disaster happens, but when!




All of this week's top headlines to your email every Friday.


 
 

 
DoD
Untitled-1

DoD highlights warrior, family care during Warrior Care Month 2014

The Defense Department recently hosted a rehabilitation expo as part of Warrior Care Month as it continues its commitment to supporting wounded, ill and injured troops, their families and caregivers. James Rodriguez, deputy ass...
 
 

Virtual Hope Box mobile app grows in popularity

A free smartphone app that helps people in crisis remember good things in their lives has been downloaded 13,000 times in the past six months, according to data from app stores. That’s good news for experts at the National Center for Telehealth & Technology (T2), which developed the Virtual Hope Box app to help users...
 
 
Courtesy Photo

Tinker epitomized Native American strength, leadership

Courtesy Photo Maj. Gen. Clarence L. Tinker was a natural leader who personally led his Airmen into combat missions during the early days of World War II. He perished, along with his crew, during the battle of Midway. The natio...
 

 
(U.S. Air Force photo/Sarah Corrice)

AF tests first all-electric vehicle fleet in California

(U.S. Air Force photo/Sarah Corrice) Airmen from Los Angeles Air Force Base learn how to use charging equipment for the base’s new electric vehicle fleet during a training demo Oct. 31, 2014, in El Segundo, Calif. When not in...
 
 

AF expands digital library content for Airmen

JOINT BASE SAN ANTONIO-RANDOLPH, Texas (AFNS) — Airmen at 19 Air Force installations around the world will soon have access to a new 200-title audiobook and eBook digital library, Air Force officials said. The 19 participating installations will help test digital content distribution using the new Air Force eReader AERO; a single portable device developed...
 
 

Air Force officials update AF Instruction 1-1

WASHINGTON (AFNS) — Air Force officials approved Air Force Instruction 1-1, Air Force Standards, Nov. 7, to clarify guidance on Airmen’s religious rights and commanders’ authority and responsibility to protect those rights. The changes come as a result of a Religious Freedom “Focus Day” earlier this year when leaders in the Air Force’s chaplain corps...
 




0 Comments


Be the first to comment!


Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>


Directory powered by Business Directory Plugin