Facts About Earthquakes

Year	Location	Magnitude	Comments
1663 & 1870	St. Lawrence River region, Canada
1755	Boston/Cape Ann, Massachusetts	*6.0	Buildings damaged.
1811 & 1812	New Madrid, Missouri	*Between 7.2 and 8.3	Experienced the three largest earthquakes known to have occurred in North America. 203 damaging aftershocks recorded. Soil liquefaction occurred.
1868	Ka’u District, Island of Hawaii	*7.9	77 people died.
1884	New York City area
1886	Charleston, South Carolina	*6.8	Soil liquefaction occurred. Extensive damage; 60 people or more died. Over 400 aftershocks over the next 30 years.
1895	Charleston, Missouri
1897	Giles County, Virginia
1899	Yakutat Bay, Alaska	*8.0

1931	Valentine, Texas	*6.4	The largest earthquake to hit Texas in historic times.
1935	Timiskaming, Ontario (Canada)
1938	Shumagin Island, Alaska	8.2
1946	Unimak Island, Alaska	8.1	165 people died. Alaska experiences as many as 4,000 earths per year of varying magnitude. Since 1899, 39 earthquakes of 7.0 or greater magnitude have been recorded in Alaska.
1947	Michigan	4.4
1964	Prince William Sound, Alaska	9.2	125 people died.
1975	Kalapana, Hawaii	7.2	2 people died.
1979 & 1980	New York State and the adjacent areas	Between 1.0 and 5.0	131 earthquakes experienced in the region.
1980	North of Philadelphia, Pennsylvania.		5 earthquakes recorded.

In the table above, the magnitudes of earthquakes with asterisks (*) that took place in the 1800's are described as estimated. This is because these earthquake events took place before the Richter magnitude scale was put in place. The approximation is made by a study of accounts of the earthquake which are correlated with the damage described in the Mercalli Intensity Scale.

The Mercalli Scale allows a classification of an earthquake's magnitude by people who record historic and other major local or regional events in addition to seismologists. The descriptions may come even from personal correspondence or records maintained by average citizens. Such records frequently include extensive and descriptive details about the damage the earthquake caused.

It is estimated that over 900,000 earthquakes occur worldwide each year. Fortunately, the vast majority of them are magnitude 2.5 or less. Great or “big” earthquakes (magnitude 8.0 or more) only occur about once every 5 to 10 years. Most of these great or “big” quakes occur along the plate boundaries, not in the Eastern and Midwestern U.S.

A few areas of the Midwestern and Eastern United States are more prone to earthquakes than others.[1] The most earthquake-prone areas include Charleston, South Carolina, eastern Massachusetts, the St. Lawrence River area, and the central Mississippi River Valley. Others sections of this part of the country are prone to earthquakes, but can expect fewer quakes of smaller magnitude. Below is a map showing the risk of damage by earthquakes for the continental United States.

U.S. Earthquake risk Map

Waiting For The Big One: A Lesson From History

As is typically the case with earthquakes, without warning, at 5:04 p.m. on October 17, 1989, while 62,000 spectators assembled in San Francisco's Candlestick Park for the World Series, the west side of the San Andreas Fault lurched northward and upward, violently shaking northern California for about 15 seconds. Within minutes, news of the quake had spread around the world. Suddenly, Bay Area residents faced much bigger problems than choosing between the Giants and the A's.

The Cypress Street section of Interstate 880 in Oakland collapsed. Downtown Santa Cruz was ravaged. An upper roadway span of the Bay Bridge fell. Many houses and apartment buildings in the Marina District of San Francisco were destroyed or damaged beyond repair. The death toll was 63, major and minor injuries totaled more than 4,000, and property damage was estimated at $6 billion. Some 13,000 people were displaced from their dwellings by quake damage.

As bad as it was, this was not quite the great earthquake that Californians have long feared. For one thing, its epicenter was just west of Loma Prieta Mountain, some 10 miles northeast of Santa Cruz and 60 miles south of San Francisco. If the epicenter had been closer to the major urban areas, casualties and damage would have been considerably higher.

For another, the Loma Prieta Earthquake (as it is now being called by seismologists) rated around 7.0 on the Richter scale--a major but not a great earthquake. In contrast, the great San Francisco quake of 1906 is thought to have been about 8.3. The disastrous Mexico City quake of 1985 was measured at 8.1, and the Alaskan quake of 1984 registered 8.6.

On the Richter scale[1], every unit increase represents more than a thirty fold increase in energy released. For example, an 8.0 quake is more than 30 times more powerful than a 7.0.

With this in mind, and having lived through the 1989 quake, we can begin to imagine what a great earthquake might be like. The longer and stronger shaking would multiply the destruction many times over.

In urban areas, [2]thousands would die and tens of thousands would be seriously injured. Medical facilities, many of which would suffer damage themselves, would be overwhelmed. A great earthquake would do what the 1989 quake did, only more so. It would interrupt communications and transportation for days, even weeks. It would break electric, gas, water, sewer, and telephone lines, topple radio and TV towers, weaken or bring down bridges and overpasses, and block roadways. Airports would be out of commission for days. For a while, foot and bicycle would probably be the only reliable means of transportation.

With communications disrupted and personnel scattered, authorities would be swamped by requests for emergency assistance. Federal, state, and local governments would probably be unable to help people with basic survival for some time. In the meantime[3], you, your family, your friends, and your neighbors would be on your own.

[1] For more on the Richter scale, see Appendix I.

[2] Experts have estimated that a great earthquake on the San Andreas fault in the San Francisco area would cause 3,000 to 11,000 deaths, 12,000 to 44,000 injuries, and $20 billion or more in damage. Casualties and damage would be less, though still extensive, in case of a great quake on the Hayward fault in the East Bay. Another estimate indicates that a great quake in southern California would kill from 3,000 to 14,000 people, injure 12,000 to 55,000 severely enough to require hospitalization, and cause $20 billion in damage.

[3] Even moderate shakes can cause extensive damage. Recent examples in California include the 1983 Coalinga quake (Richter 6.7) and two in the Los Angeles area: the San Fernando Valley quake of 1971 (6.4) and the Whittier quake of 1987 (5.9). The Whittier quake killed seven people, injured more that 100, damaged 10,000 buildings, and caused over $200 million in losses. A great 8.0 quake would be about 1,000 times more powerful than the Whittier quake and around 175 times as strong as the 1971 San Fernando quake.

Facts About Earthquakes

Appendix I.

Specific Facts About Earthquake Events and Damage

Earthquake Damage

· Earthquake damage at a given point depends on several factors: size of the quake (its magnitude);

· nature of the movement along the fault;

· depth of the quake below the surface;

· distance from the epicenter;

· type of soil and rock layers transmitting the quake's energy;

· season of the year (more landslides in wet weather);

· and, of course, population density and types of buildings in the affected area.

Magnitude and Intensity: The Richter and Modified Mercalli Scales

Magnitude describes the size of the earthquake itself in terms of total energy released. The familiar Richter Scale is a magnitude scale.

Intensity---how much the ground shakes at a given point on the surface---is what matters when it comes to damage and death. But intensity doesn't really describe how big the earthquake is.

There are several different scales for measuring the magnitude of earthquakes. The most familiar is the Richter Scale, which is based on the amplitude of the quake's largest seismic wave (ground motion). Because the Richter Scale is logarithmic, an increase of one unit in magnitude indicates a tenfold increase in the size of the quake. In turn, a tenfold increase in size represents 31.6 times as much energy released.

So every unit increase in the Richter Scale means an earthquake roughly 32 times more powerful. A quake of Richter magnitude 6.0 has almost 32 times the energy of a 5.0, and nearly a thousand times as much energy as a 4.0 (31.6 x 31.6 = 998.6).

An increase of half a unit in the scale indicates 5.6 times as much energy. A 6.5 quake on the Richter Scale is nearly six times as big as a 6.0; a 7.5 is about 32 times more powerful than a 6.5; and so on.

The Modified Mercalli Intensity Scale ranges from I to XII and describes a quake's effects on people and buildings at a given point on the earth's surface. People do not generally feel intensities below III or IV. Minor structural damage, like cracks in walls and chimneys, usually begins with intensities of VI. Moderate damage occurs in the VII-VIII range; major damage at IX and X; and devastation at XI and XII.

An earthquake has different intensities at different locations. The maximum intensity is usually at or near the source of the quake (its epicenter), and the intensity diminishes with distance from the epicenter. How much or how fast it diminishes depends on the nature of the subsurface rocks that carry the quake's waves.

In California, where relatively soft, young substrata dampen and absorb the waves, even fairly strong quakes are rarely felt more than a few hundred miles from their centers. East of the Rocky Mountains, earthquakes are less common, but the strata are older and harder, and quake energy travels much farther. In June 1987, the moderate 5.0 shake centered in Lawrenceville, Illinois was felt in at least 16 states. In 1811 and 1812 three (3) great earthquakes struck along the New Madrid (Missouri) Fault near Memphis, Tennessee and rattled buildings in Boston, 1100 miles away. One of them is now estimated to have been Richter magnitude of 7.8.

Table I. Average Number of Earthquakes
Richter Magnitude	Per Year in the World	Per 100 Years in California	Duration of Strength Shaking (seconds)
8.0-8.9	1	1	30-90
7.0-7.9	15	12	20-50
6.0-6.9	140	80	10-30
5.0-5.9	900	400	2-15
4.0-4.9	8000	2000	0-15

Lessons of the 1906 San Francisco Earthquake

The San Francisco earthquake of 1906 was an even greater disaster than the city admitted at the time. Listed below

Casualties: The official Army estimate of 498 dead represents only a fraction of the fatalities. Recent research indicates that at least 2500 were killed, probably many more.

Hardest hit was a five to six square-mile area of San Francisco south of Market Street, between 11th and Townsend, where wooden, brick, and masonry buildings several stories high were jammed together. Many collapsed and some burned. Of 100,000 people who lived there, 1,000 died.

Damage: Some 28,000 buildings were destroyed, and hundreds of thousands of people had to flee their homes. A hundred major fires broke out, many caused by ruptured gas lines, while firefighters were nearly helpless because of broken water mains. Yet fire damage, though considerable, was not as extensive as claimed.

Covering up the truth: In the aftermath of the quake, because they didn't want to scare off the Eastern capital and credit San Francisco needed to rebuild, city officials minimized the deaths and the damage in their public statements.

Though City Hall lay in ruins, Mayor Eugene Schmitz claimed the government was functioning normally and denied reports of looting and civil disorder. (Meanwhile, he issued orders to army and police personnel to shoot looters on sight.) Schmitz said that the earthquake produced "absolutely no change" in the effectiveness of the police and fire departments, which were already overwhelmed. In fact, San Francisco almost fell apart for a few days. There was widespread looting and arson. Life for refugees in the Golden Gate Park tent city was no picnic. Many San Francisco residents left the city and even the Bay Area right away, never to return.

Fraud was in the air, and private citizens were as heavily involved as the city government. Since insurance policies usually excluded earthquake damage, few claimants admitted that their buildings had been damaged by ground movement. Instead, homeowners and businessmen blamed everything on fire. Insurance companies offered thousands of dollars for photographs showing that buildings had collapsed instead of burning as alleged. Total damage was estimated around $500 million. Eventually, the companies paid some 90,000 settlements totaling $230 million - or roughly $5 billion in 2007 dollars.

Facts About Earthquakes

Appendix II.

Earthquake Insurance

Even moderate quakes can cause property damage. In order to make a decision regarding whether earthquake insurance should be purchased, several items need to be considered. Specifically, in addition to their deductible clauses, many earthquake insurance policies exclude damage to masonry, including fireplaces and exterior stucco.

After considering the above issues, earthquake insurance may still be a good investment. Before you buy or renew earthquake insurance, consider the following questions:

1. Is your home (or business office, etc.) on geologically stable ground?

2. Is your home constructed of wood, or of unreinforced masonry and/or brick?

3. Is your home properly bolted to an adequate foundation?

4. Would your home be affected if neighboring structures collapse or burn?

5. If you have no earthquake insurance and your home is heavily damaged or totally destroyed, could you afford to repair or replace it with personal savings? In such circumstances, could you arrange for adequate credit?

6. Will your insurance company survive the quake and the ensuing blizzard of claims in good enough financial condition to pay your claim? Or will it file for reorganization under the Chapter 11 bankruptcy laws, leaving you without – or difficulty accessing - the resources needed to repair/rebuild your home?

Facts About Insurance Coverage for Earthquakes in the United States

Standard homeowners, renters and business insurance policies do not cover damage from earthquakes. Coverage is available either in the form of an endorsement or as a separate policy for homeowners, renters and small business owners. Unlike flood insurance, earthquake coverage is available from private insurance companies rather than from the government. In California, homeowners can also get coverage from the California Earthquake Authority (CEA), a privately funded, publicly managed organization.

Earthquake insurance provides protection from the shaking and cracking that can destroy buildings and personal possessions. Coverage for other kinds of damage that may result from earthquakes, such as fire and water damage due to ruptured or severed gas and water pipes, is provided by standard home and business insurance policies. Cars and other vehicles are covered for earthquake damage by comprehensive insurance which also provides protection against flood and hurricane damage as well as theft.

Deductibles and Costs

Earthquake insurance carries a deductible, generally in the form of a percentage rather than a dollar amount. Deductibles can range anywhere from 2 percent to 20 percent of the replacement value of the structure. This means that if it cost $100,000 to rebuild a home and there was 2 percent deductible, the consumer would be responsible for the first $2,000 dollars. Insurers in states like Washington, Nevada and Utah, with higher than average risk of earthquakes, often set minimum deductibles at around 10 percent. In most cases, consumers can get higher deductibles to save money on earthquake premiums.

The standard CEA policy includes a deductible that is 15 percent of the home’s replacement cost. The basic policy covers only the house (other structures such as garages, pools, etc. are not covered). Personal possessions are covered up to $5,000 and “loss of use” expenses, the additional cost of living elsewhere while home repairs are made, are covered up to $1,500. Recognizing that some people want more comprehensive coverage, the CEA now offers a 10 percent deductible, insurance for other structures, personal items coverage up to $25,000 and $10,000 in “loss of use” coverage.

Premiums vary widely among the 19 rating territories, based on the type of house, its age, the nature of the soil, and proximity to known fault lines. The average cost statewide is $500, but it can exceed $3,000 a year. The CEA currently has reserves of more than $7 billion. Because of high deductibles, this amount is considered enough to cover two earthquakes as severe as the 1994 Northridge quake, which caused an estimated $12.5 billion in insured losses.

Premiums also differ widely by location, insurer and the type of structure that is covered. Generally, older buildings cost more to insure than new ones. Wood frame structures generally benefit from lower rates than brick buildings because they tend to withstand quake stresses better. Regions are graded on a scale of 1 to 5 for likelihood of quakes, and this may be reflected in insurance rates offered in those areas. The cost of earthquake insurance is calculated on “per $1,000 basis.” For instance, a frame house in the Pacific Northwest might cost between one to three dollars per $1,000 worth of coverage, while it may cost less than fifty cents per $1,000 on the East coast.

A brick home would cost approximately $3 to $15 dollars per $1,000 in the Pacific Northwest, while it would cost between 60 to 90 cents in New York. Earthquake insurance is available from most insurance companies in most states.

California law requires homeowners’ insurance companies to offer earthquake coverage to their homeowners’ insurance policyholders. Homeowners can decide to purchase it, purchase a policy from another insurer, or decline it altogether.

Document Your Case With A Camera/Video Recording

To protect your interests in case of insurance claims or declared losses for tax purposes, make photographic records of the damage to your property.

Take a set of exterior and interior photos of your home now. Label and date each print or slide. Storing three (3) copies of the photos in separate safe places is recommended. Specifically, you should use the following storage location:

1. your safety deposit box,

2. a fire proof safe at home with your financial records and

3. an electronic vault that is Internet accessible.

As soon as possible after the quake, take another set of photos corresponding to the first set and showing the damage.

In both the "before" and "after" photos, consider marking the date clearly on a large card and including it (and, if possible, a current newspaper) in each shot. You might also have neighbors sign and witness statements about the extent of the damage and how it occurred. These records might be worth thousands of dollars to you in future tussles with your insurance company or the IRS.

[1] The central Mississippi River Valley and the Charleston, South Carolina area, are more prone to damage during earthquakes than the northern part of the country. These areas have sandy soils that shake more than solid rock, resulting in damage from subsidence during an earthquake. The high water tables along the Mississippi and near the coast also increase the risk of soil liquefaction.

1980	Kentucky	5.1
1982	New Brunswick, Canada	5.7
1982	Arkansas	Four recorded at Between 4.0 and 4.5	Multi-year earthquake “swarm”. Eighty-eight earthquakes between June 24 and July 5, 1982. Four earthquakes of significant magnitude during first 3 months of swarm. Between 1982 and 1985, total of approximately 40,000 earthquakes in the area (most very small or not felt)
1983	Lake Charles, Louisiana	3.8
1983	Indiana	5.9
1986	Painesville, Ohio	4.9	Several aftershocks. The earthquake was felt in 11 states.
1987	Southeastern Illinois	5.2	This area has had 7 earthquakes of magnitude 4.5 or greater since 1892.