Expert Says To Expect More Aftershocks
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SHERIFF INSPECTS DAMAGE - White County Sheriff Doug Maier inspected this crack running from the ground to the roof of the northeast corner of the City-County Jail in Carmi Friday morning. The damage is believed to have been caused by a 5.2 magnitude earthquake that struck the area around 4:37 a.m. and was centered neared West Salem. --Times photo/Braden Willis |
An earthquake measuring 5.2 on the Richter scale hit southern Illinois at 4:37 a.m. Friday, causing some minor structural damage in the area, including damage at the City-County Jail and the White County Courthouse in Carmi.
The quake was centered about halfway between West Salem and Mt. Carmel, to the northwest of Mt. Carmel and southeast of West Salem, according to the U.S. Geological Survey (USGS). The USGS reported the quake was 7.2 miles deep. The initial report indicated the quake measured 5.4, but it was revised to 5.2 shortly thereafter.
The 5.4 measurement matched a 1968 quake in the area that caused some damage.
White County Sheriff Doug Maier inspected the jail Friday morning and confirmed there was damage to the structure. He told The Times the damage affected three outside corners of the brick structure of the jail, two interior walls of the jail and a small area above an old coal chute on the outside brick wall of the west side of the Courthouse.
The damage to the Courthouse was very minor, while the damage to the jail was more significant. The cracks on the outside walls ran from the ground to the roof on both sides of the corners on the northeast and southeast corners. The interior cracks were very slight.
Maier said he would check with the county's insurance carrier about the damage and costs to repair it.
Carmi Police Chief Mike Thomas said he had received a few reports of minor structural damage to some residences. He was unaware of any damage to commercial structures. There were reports of merchandise being rattled off shelves in some stores. Many area residents reported being awakened by the quake.
Municipal utility crews in Carmi and the surrounding towns were busy checking power lines, while Consumers Gas Co. officials said they were swamped with calls about possible gas leaks, though all of them, as of 8:50 a.m. Friday, had been unfounded, including one report near Iris Lane in Carmi. Crews farther north, nearer the epicenter of the quake, were also busy checking gas and utility lines as reports or concerns of leaks poured in.
The quake was felt as much as 300 miles away, with reports of skyscrapers swaying in Indianapolis and residents in all the surrounding states reporting having felt the quake.
Some reports of minor to moderate damage were reported to some structures nearer the epicenter, including residents reporting dishes being cracked and bricks being shaken free from structures in Albion, Bridgeport, New Harmony, Ind., and Grayville.
In downtown Grayville, a ceiling fell in at Hair Gallery in the 100 block of East North Street. Steve Hartsock of the Navigator newspaper in Grayville said his residence had cracks in some plaster and, at the newspaper office, a clock fell off a wall and broke.
Rick Atterberry of the University of Illinois Extension reported that some experts' opinion is that today's earthquake may be followed by an aftershock or aftershocks, but there is no way to predict their strength. One USGS geologist quoted this morning cautioned that there is a very slim chance this could be a pre-shock to something bigger. Atterberry provided a link to a FEMA site about earthquake preparedness and response: http://www.fema.gov/hazard/earthquake/eq_before.shtm
Extension is hosting a conference May 6 and 7 on the New Madrid seismic zone and earthquake preparedness. For more information visit, the following web address: http://web.extension.uiuc.edu/state/newsdetail.cfm?NewsID=10042
The registration deadline is April 22, but Extension officials said they will accept registrations until April 25. The fee is $40.
Atterberry added that gas leaks sometimes can occur in relatively minor earthquakes, especially at connections to furnaces and water heaters.
Water heaters can be somewhat top heavy and are prone to falling over, so he recommended following local building codes regarding strapping them to a wall and using flexible gas lines. He cautioned to never attempt to repair a gas leak oneself.
Evacuate the building and call 911 before calling the utility company or a plumber. This would be a good time to review how to shut off gas at one's meter if it can be done safely in an incident. Notice if a wrench or any special tools are needed and keep the tools in a handy location.
According to the USGS, the Richter magnitude scale, or more correctly local magnitude ML scale, assigns a single number to quantify the amount of seismic energy released by an earthquake. It was developed in 1935 by Charles Richter in partnership with Beno Gutenberg, both of the California Institute of Technology.
The scale was originally intended to be used only in a particular study area in California, and on seismograms recorded on a particular instrument, the Wood-Anderson torsion seismometer.
Because of the limitations of the Wood-Anderson torsion seismometer used to develop the scale, the original ML cannot be calculated for events larger than about 6.8. Events with magnitudes of about 4.6 or greater are strong enough to be recorded by any of the seismographs in the world.
The following information describes the typical effects of earthquakes of various magnitudes near the epicenter. Intensity, and thus ground effects, depends not only on the magnitude, but also on the distance to the epicenter, the depth of the earthquake's focus beneath the epicenter and geological conditions (certain terrains can amplify seismic signals).
Earthquakes measuring less than 2.0 are classified as micro-earthquakes and generally are not felt. Seismographs around the world record about 8,000 of these events per day.
Earthquakes measuring 2.0-2.9 are classified as minor are also generally not felt and there are about 1,000 of these recorded per day.
Going a little higher on the scale, from 3.0-3.9, still classifies the quake as minor, though quakes of this magnitude are usually felt. However, they rarely cause damage. Seismographs record about 49,000 of these per year around the world.
From 4.0-4.9 many people begin to notice light shaking of indoor items and may report rattling noises. Significant damage is unlikely. There are about 6,200 earthquakes this powerful measured each year.
Quakes like the one Friday, measuring between 5.0-5.9, are classified as moderate and can cause major damage to poorly constructed buildings over small regions. At most, slight damage may result to well-designed buildings. There are usually about 800 quakes of this magnitude per year.
Quakes measuring 6.0-6.9 are classified as strong and can be destructive in areas up to about 100 miles across in populated areas. Only about 120 of these are reported per year.
Major quakes measuring 7.0-7.9 can cause serious damage over larger areas. There are about 18 quakes hitting this level per year, while quakes measuring 8.0-8.9, classified as "great," can cause serious damage in areas several hundred miles across. Only about one quake this powerful is reported per year.
About every 20 years worldwide, a quake measuring 9.0-9.9 is reported. Quakes this strong are, of course, devastating. There has never been a recorded quake that measured more than 9.9.
According to the USGS' website, earthquakes in the Illinois Basin, Ozark Dome Region, are located in a large region bordering the seismically active New Madrid seismic zone on the seismic zone's north and west. The Illinois Basin, Ozark Dome Region, covers parts of Indiana, Kentucky, Illinois, Missouri and Arkansas and stretches from Indianapolis and St. Louis to Memphis.
Moderately frequent earthquakes occur at irregular intervals throughout the region. The largest historical earthquake in the region (magnitude 5.4) damaged southern Illinois in 1968. Moderately damaging earthquakes strike somewhere in the region each decade or two, and smaller earthquakes are felt about once or twice a year.
In addition, geologists have found evidence of eight or more prehistoric earthquakes over the last 25,000 years that were much larger than any observed historically in the region.
Earthquakes in the central and eastern U.S., although less frequent than in the western U.S., are typically felt over a much broader region. East of the Rockies, an earthquake can be felt over an area as much as ten times larger than a similar magnitude earthquake on the west coast.
A magnitude 4.0 eastern U.S. earthquake typically can be felt at many places as far as 60 miles from where it occurred, and it infrequently causes damage near its source. A magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 300 miles from where it occurred, and sometimes causes damage as far away as 25 miles.
Earthquakes everywhere occur on faults within bedrock, usually miles deep. Most bedrock in the Illinois Basin, Ozark Dome Region, was formed as several generations of mountains rose and were eroded down again over the last billion or so years.
At well-studied plate boundaries like the San Andreas fault system in California, often scientists can determine the name of the specific fault that is responsible for an earthquake. In contrast, east of the Rocky Mountains this is rarely the case.
The Illinois Basin, Ozark Dome Region, is far from the nearest plate boundaries, which are in the center of the Atlantic Ocean, in the Caribbean Sea and in the Gulf of California. The region is laced with known faults but numerous smaller or deeply buried faults remain undetected.
Even the known faults are poorly located at earthquake depths. Accordingly, few earthquakes in the region can be linked to named faults. It is difficult to determine if a known fault is still active and could slip and cause an earthquake.
Tim Larson of Urbana knew what was happening.
"It woke me up this morning," said Larson, a geophysicist who monitors earthquakes at the Illinois State Geological Survey at the University of Illinois. "I knew it was a significant earthquake at some distance away.
"We've had reports of damage as far away as Louisville, bricks falling, that kind of thing," Larson said.
The last major earthquake to hit Illinois had an epicenter close to today's.
In 1987, a 5.0 earthquake struck with an epicenter about 100 miles south of Champaign, close to the Wabash Valley fault system, on the Illinois/Indiana border. "It's amazing how on schedule this is," Larson said. "We have earthquakes there every 20 years."
There was a a 5.5 earthquake near Broughton on Nov. 9, 1968, and the 5.1 quake on June 10, 1987
The area prone to occasional earthquakes is called the Wabash Valley Seismic Zone, Larson said. Scientists are not sure what causes the quakes in that area, but there are old faults in the earth's crust in that zone. The relationship between these new quakes and those old faults is not clear, he said.
"It's almost like there is a weakness in the earth's crust," in the Wabash Valley zone, Larson said. "It's like an old scar being torn off. Normally, we have quakes where the faults bump against each other."
The New Madrid Zone further south in Illinois produces very powerful quakes, but it is not clear if there's any connection between the New Madrid zone and the Wabash Valley zone.
"That's a point of research," he said.
The biggest earthquake to hit Illinois in the last century, according to the Illinois State Geological Survey, was the 5.5 tremor in 1968. There have been more than 160 earthquakes in Illinois since records began in 1795, 80 percent of them in the southern half of the state.
Timothy Gress of the Mid-American Earthquake Center said the tremor was possibly related to the Wabash Valley fault.
"It's relatively active," said Gress, whose children were awakened by this morning's tremor. "We at the center are involved with the Federal Emergency Management Agency, modeling effects of what would happen if there were a major tremor. Indiana is particularly interested in this."
Toledo resident Betty Enigk remembers the 1968 earthquake that moved furniture across her tile floor.
She has carpet now, but a Friday morning tremor still managed to “jingle” the dishes in her china cabinet and alarm her black lab “Willy,” she said.
Enigk was just sitting down at her computer with a fresh cup of coffee when the earthquake struck. Living adjacent to Illinois Route 121, “I thought a big truck was going by,” she said.
“But the truck never came. It just felt like it was going on and on and on. The house was just moving under my feet. (Then) I knew it was an earthquake.”
When she let Willy back into the house, “He just about barreled me down. His hair was bushed out,” Enigk said.
The largest earthquake felt in Illinois in four decades startled area residents early Friday morning but apparently did little else.
The U.S. Geological Survey said the 5.2 magnitude tremor began at 4:37 a.m. at its epicenter five miles northeast of Bellmont, about 90 miles southeast of Coles County. A 4.6 magnitude aftershock at 10:14 a.m. — which could be felt in Coles and neighboring counties — originated eight miles east of West Salem, near the epicenter of the original quake, said the USGS.
The National Earthquake Center recorded three other aftershocks measuring 2.5, 2.5 and 2.6.
“We’ve had no reports at all” of destruction from the first earthquake, said Tom Watson, Coles County Emergency Management Agency director, at about 10 a.m. Friday.
Sheriff’s offices in area counties said they were flooded with 911 calls shortly after the initial tremor.
At about 5 a.m., Mattoon firefighters responded to a report of gas odor at a gas station on 21st Street, but they found no evidence of a gas line break.
Mattoon Building Inspector Kyle Gill said no one notified him of any structural damage, especially to brick or masonry walls.
“The earthquake woke me up and I thought this could cause some problems with bricks, but we’ve not had any reports this morning,” Gill said.
Charleston Public Works Director Curt Buescher said crews were asked early in the day to be on the lookout for earthquake-related damage to water/sewer lines or other city infrastructure. He said no damage had been called in as of late Friday morning.
“Hopefully, there won’t be any damage at all,” Buescher said.
In Clark County, which of the area counties is among the nearest to the epicenter, EMA Deputy Director Michael Duvall said the earthquake “was felt in all parts of the county.”
Friday morning’s quake rivaled the magnitude 5.3 event in 1968 that started in Hamilton County in Southern Illinois, said the USGS. Prior to that, the largest quake felt in Illinois originated in Missouri in 1895, according to the USGS.
Rural Charleston resident Ann Bacon also was awake and reading the newspaper when the temblor hit.
“At first I thought it was some kind of explosion,” she said.
“And then I thought, ‘No, it’s a tornado.’”
She said her dishes and windows began “chattering.” Then she went outside, and realized what had happened.
“All of the animals — there was just noise,” she said. “The critters were up and something was wrong. It was a very odd morning.
“I’ve never experienced anything like that. (It) was very eerie and very scary for those few seconds.”
For many in the Midwest, Friday got off to a shake, rattle and roll when a 5.2 magnitude earthquake, centered near West Salem, Ill., let loose.
The 5:37 a.m. quake was felt from Atlanta to Michigan and awoke many Lawrence and Orange County residents who felt the second strongest quake to hit Illinois.
Bedford North Lawrence High School junior Kaleb Kirkman of Avoca said he was sitting on the back deck of his house when the quake occurred.
“It started shaking the whole house,” he said. “ I thought our house was falling down. I hang everything up in my room. Stuff was falling off my walls.”
With the rarity of earthquakes in the Midwest, many, including Josh Nicholson, weren’t sure what was happening.
“I just got out of bed whenever it started. I thought I was still dreaming because everything started shaking,” said Nicholson, a BNL junior. “I didn’t know what was going on. My mom came running in and thought it was a tornado or something. My bed was clanging up against the wall and making all kinds of racket and a couple of pictures fell off my shelf.”
Earthquakes take on added relevance for those who have experienced them in California, where the phenomenon is more common.
“I knew it was an earthquake,” Jean Bower said.
The Bedford resident added, “The bed was shaking real bad and the bathroom door, I could feel it shaking, and it (the tremor) knocked two little things off the wall in the back bedroom. The reason I knew this (was an earthquake) is because I lived in California in 1952. ... My husband was in the Navy and so I lived in Long Beach and this aftershock came from San Diego. ... It scares you to death. It did then, too.”
Amanda Vernon, from southern Orange County, was a youngster living in California when one of the more powerful earthquakes in recent times hit in 1989.
Still, Vernon wrote in an e-mail, “It took me the longest time to figure out this was earthquake. Naturally, I thought it was a tornado or strong winds.”
Vernon told her husband, Sam, they needed to get in the basement, but he went outside and realized there was no wind activity.
“It has me thinking about the earthquake of ’89,” Vernon said. “We lived in the Fresno area and its epicenter was outside of San Francisco, but we still felt it much stronger than this quake today.”
Springville resident Steve Kimmel, when he went outside during the quake, noticed a strange accompaniment.
“At the time this was happening, my husband went out on the front porch, looked up and noticed the moon was blood red,” said Kimmel’s wife, Elayne.
The quake is believed to have involved the Wabash fault, a northern extension of the New Madrid fault about 6 miles north of Mount Carmel, Ill., said United States Geological Survey geophysicist Randy Baldwin.
The last earthquake in the region to approach the severity of Friday’s temblor was a 5.0 magnitude quake that shook a nearby area in 2002, Baldwin said.
“This is a fairly large quake for this region,” he said. “They might occur every few years.”
The earthquake center is 100 miles from Bedford. And the tremors were noticed as far away as Atlanta, Chicago, St. Louis and Cincinnati. Officials say no injuries have been reported and only minor damage.
“It shook our house where it woke me up,” said David Behm of Philo, 10 miles south of Champaign. “Windows were rattling, and you could hear it. The house was shaking inches. For people in central Illinois, this is a big deal. It’s not like California.”
Lucas Griswold, a dispatcher in West Salem, said the Edwards County sheriff’s department received reports of minor damage and no injuries.
“Oh, yeah, I felt it. It was interesting,” Griswold said. “A lot of shaking.”
Indiana State Police spokesman Sgt. Todd Ringle in Evansville said there were no immediate reports of damage.
Steve Jenkins, vice president, gasification services for CH2MHill, an engineering company, was in a Mattoon motel Thursday night prior to attending the Coles Together annual meeting.
A Florida resident, Jenkins said he has experienced hurricanes and tornadoes.
“But I will always remember where I was at 4:37 a.m. today when I felt an earthquake,” he said.
The latest quake was triggered in the Ozark Dome Region of the Illinois Basin, which borders the “more seismically active” New Madrid seismic zone to the north and west, according to the USGS.
The Ozark Dome Region “is far from the nearest plate boundaries, (and) the region is laced with known faults, but numerous smaller or deeply buried faults remain undetected,” said the USGS report.
Staff Writer Rob Stroud contributed to this story.
Contact Nathaniel West at nwest@jg-tc.com or 238-6860. Contact Herb Meeker at hmeeker@jg-tc.com or 238-6869.
Magnitude 6.8 WASHINGTON
2001 February 28 18:54:32 UTC
Preliminary Earthquake Report
U.S. Geological Survey, National Earthquake Information Center
World Data Center for Seismology, Denver
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 | Date-Time | 2001 02 28 18:54:32 UTC | | Location | 47.14N 122.72W | | Depth | 52.0 kilometers | | Magnitude | 6.8 | | Region | WASHINGTON | | Reference |
| | Source | USGS NEIC | |  |
The preliminary mechanism for this earthquake is tensional (normal) faulting in the subducting (downgoing) Juan de Fuca Plate, caused by bending of the plate. Damage and injuries have occurred in the Olympia-Seattle area. This earthquake is located in the same general area as a magnitude 7.1 earthquake on April 13, 1949. The location for this earthquake was furnished by the Geophysics Program, University of Washington, Seattle.
About 400 people injured and major damage in the Seattle-Tacoma- Olympia area. Maximum intensity (VIII) in the Capitol Hill area of Olympia and in the Pioneer Square area south of downtown Seattle. Preliminary estimates of damage are between 1 and 4 billion U.S. dollars. Felt from central Oregon to southern British Columbia and as far east as northwestern Montana. The maximum recorded acceleration was 0.3g at Seward Park. Landslides occurred in the Tacoma area and near Renton. Liquefaction and sand blows occurred in parts of Olympia and South Seattle.
No aftershocks were recorded by the University of Washington network in the first 6 hours following the magnitude 6.8 main shock. In a typical aftershock sequence, the highest rate of aftershock activity occurs during this period. Earthquakes of comparable magnitude with nearby epicenters and similar depths occurred in 1949 and 1965. The 1949 earthquake had only one aftershock in the following six months, and little aftershock activity was observed following the 1965 earthquake. On the basis of this information, we do not expect significant aftershocks from today's earthquake. The depths (50-70 km) of these three earthquakes may be a factor in their low aftershock productivity. Shallow (less than 20 km) mainshocks are more likely to have energetic aftershock sequences.
24-Hour Aftershock Forecast Map
Click on the map to zoom in.
This is a time-dependent map giving the probability of strong shaking at any location in California within the next 24-hours. For this purpose, “strong shaking” is defined as Modified Mercalli Intensity (MMI) VI, or the level of shaking that throws objects off shelves.
What Are Aftershocks, Foreshocks and Earthquake Clusters?
The calculations in this system are based on known behaviors of aftershocks. Scientists have shown that the rules governing aftershock behavior also apply to "aftershocks" that are larger than their main shock - i.e., the possibility that the first event was a foreshock. These rules include:
Aftershock Facts: In a cluster, the earthquake with the largest magnitude is called the main shock; anything before it is a foreshock and anything after it is an aftershock. A main shock will be redefined as a foreshock if a subsequent event has a larger magnitude. The rate of main shocks after foreshocks follows the same patterns as aftershocks after main shocks. Aftershock sequences follow predictable patterns as a group, although the individual earthquakes are random and unpredictable. This pattern tells us that aftershocks decay with increasing time, increasing distance, and increasing magnitude. It is this average pattern that this system uses to make real-time predictions about the probability of ground shaking.
Distance: Aftershocks usually occur geographically near the main shock. The stress on the main shock's fault changes drastically during the main shock and that fault produces most of the aftershocks. Sometimes the change in stress caused by the main shock is great enough to trigger aftershocks on other, nearby faults, and for a very large main shock sometimes even farther away. As a rule of thumb, we call earthquakes aftershocks if they are at a distance from the main shock's fault no greater than the length of that fault. The automatic system keeps track of where aftershocks have occurred, and when enough aftershocks have been recorded to pinpoint the more and less active locations, the system adjusts the probabilities on the map to reflect those local variations.
Time: An earthquake large enough to cause damage will probably be followed by several felt aftershocks within the first hour. The rate of aftershocks decreases quickly - the decrease is proportional to the inverse of time since the main shock. This means the second day has about 1/2 the number of aftershocks of the first day and the tenth has about 1/10 the number of the first day. These patterns describe only the overall behavior of aftershocks; the actual times, numbers and locations of the aftershocks are random. We call an earthquake an aftershock as long as the rate at which earthquakes occur in that region is greater than the rate before the main shock. How long this lasts depends on the size of the main shock (bigger earthquakes have more aftershocks) and how active the region was before the main shock (if the region was seismically quiet before the main shock, the aftershocks continue above the previous rate for a longer time). Thus, an aftershock can occur weeks or decades after a main shock.
Magnitude: Bigger earthquakes have more and larger aftershocks. The bigger the main shock the bigger the largest aftershock will be, on average. The difference in magnitude between the main shock and largest aftershock ranges from 0.1 to 3 or more, but averages 1.2 (a M5.5 aftershock to a M6.7 main shock for example). There are more small aftershocks than large ones. Aftershocks of all magnitudes decrease at the same rate, but because the large aftershocks are already less frequent, the decay can be noticed more quickly. Large aftershocks can occur months or even years after the main shock.
Q: Foreshocks, aftershocks - what's the difference?
A: "Foreshock" and "aftershock" are relative terms. Foreshocks are earthquakes which precede larger earthquakes in the same location. Aftershocks are smaller earthquakes which occur in the same general area during the days to years following a larger event or "mainshock", defined as within 1-2 fault lengths away and during the period of time before the background seismicity level has resumed. As a general rule, aftershocks represent minor readjustments along the portion of a fault that slipped at the time of the main shock. The frequency of these aftershocks decreases with time. Historically, deep earthquakes (>30km) are much less likely to be followed by aftershocks than shallow earthquakes. (Univ. of Washington)
