Magnitude 4.0 - = ILLINOIS

Magnitude 4.0 - ILLINOIS

2008 April 21 05:38:29 UTC

Versi=F3n=20 en Espa=F1ol

Details
Summary
Maps
Scientific=20 & Technical

Where = can I=20 find...?

Earthquake Details

Magni= tude 4.0

Date-Time<= /A>

Monday, April 21, 2008 at 05:38:29 UTC
Monday, April 21, 2008 at 12:38:29 AM at epicenter=20
Time of Earthquake in other Time = Zones

Locati= on 38.483=B0N, 87.857=B0W

Depth= 10 km (6.2 miles) set by location program

Region ILLINOIS

Dista= nces

11 km (7 miles) NW (315=B0) from Mount Carmel, = IL
12 km (7 miles) NNE (23=B0) from Bellmont, = IL
13 km (8 miles) ENE (72=B0) from Bone Gap, = IL
62 km (39 miles) NNW (335=B0) from Evansville, = IN
208 km (129 miles) E (94=B0) from St. Louis,=20 MO

Loc= ation=20 Uncertainty horizontal +/- 4.1 km (2.5 miles); depth fixed by location=20 program

Para= meters NST=3D 95, Nph=3D 95, Dmin=3D34.9 km, Rmss=3D1.36 sec, Gp=3D=20 25=B0,
M-type=3Dmoment magnitude (Mw), Version=3D8

Source

USGS NEIC (WDCS-D)

Event=20 ID us2008rcar

This event has been reviewed by a seismologist.=20
Did=20 you feel it? Report shaking and damage at your location. = You can=20 also view a map displaying accumulated data from your report and = others.=20

Earthquake Summary

The following is a release by the United States Geological Survey, = National=20 Earthquake Information Center: An earthquake occurred 35 km (20 miles) = SW of=20 Vincennes, Indiana and 205 km (125 miles) SW of INDIANAPOLIS, Indiana at = 11:38=20 PM MDT, Apr 20, 2008 (12:38 AM CDT, Apr 21, 2008 in Illinois). The = magnitude and=20 location may be revised when additional data and further analysis = results are=20 available. There have been no reports of damage.

Felt Reports

MW 4.0 (SLM). Felt widely in areas of Illinois, Indiana, Kentucky and = Missouri.=20

Tectonic Summary

EARTHQUAKES IN THE ILLINOIS BASIN - OZARK DOME REGION
=20 This large region borders the much more seismically active New Madrid = seismic=20 zone on the seismic zone's north and west. The Illinois basin - Ozark = dome=20 region covers parts of Indiana, Kentucky, Illinois, Missouri, and = Arkansas and=20 stretches from Indianapolis and St. Louis to Memphis. Moderately = frequent=20 earthquakes occur at irregular intervals throughout the region. The = largest=20 historical earthquake in the region (magnitude 5.4) damaged southern = Illinois in=20 1968. Moderately damaging earthquakes strike somewhere in the region = each decade=20 or two, and smaller earthquakes are felt about once or twice a year. In=20 addition, geologists have found evidence of eight or more prehistoric=20 earthquakes over the last 25,000 years that were much larger than any = observed=20 historically in the region.

Earthquakes in the central and eastern U.S., although less frequent = than in=20 the western U.S., are typically felt over a much broader region. East of = the=20 Rockies, an earthquake can be felt over an area as much as ten times = larger than=20 a similar magnitude earthquake on the west coast. A magnitude 4.0 = eastern U.S.=20 earthquake typically can be felt at many places as far as 100 km (60 mi) = from=20 where it occurred, and it infrequently causes damage near its source. A=20 magnitude 5.5 eastern U.S. earthquake usually can be felt as far as 500 = km (300=20 mi) from where it occurred, and sometimes causes damage as far away as = 40 km (25=20 mi).

FAULTS
Earthquakes everywhere occur on faults within = bedrock,=20 usually miles deep. Most bedrock in the Illinois basin =96 Ozark dome = region was=20 formed as several generations of mountains rose and were eroded down = again over=20 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=20 is responsible for an earthquake. In contrast, east of the Rocky = Mountains this=20 is rarely the case. The Illinois basin - Ozark dome region is far from = the=20 nearest plate boundaries, which are in the center of the Atlantic Ocean, = in the=20 Caribbean Sea, and in the Gulf of California. The region is laced with = known=20 faults but numerous smaller or deeply buried faults remain undetected. = Even the=20 known faults are poorly located at earthquake depths. Accordingly, few=20 earthquakes in the region can be linked to named faults. It is difficult = to=20 determine if a known fault is still active and could slip and cause an=20 earthquake. As in most other areas east of the Rockies, the best guide = to=20 earthquake hazards in the Illinois basin =96 Ozark dome region is the = earthquakes=20 themselves.

Earthquake=20 Information for Illinois

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Scientific & Technical Information

USGS/SLU=20 Regional Moment Tensor Solution=20
Phase=20 Data=20
Seismic=20 Record Section=20
Theoretical=20 P-Wave Travel Times

Preliminary Earthquake Report=20
U.S. = Geological=20 Survey, National Earthquake Information Center:
World Data = Center for=20 Seismology, Denver

Magni= tude	4.0
Date-Time<= /A>	Monday, April 21, 2008 at 05:38:29 UTC Monday, April 21, 2008 at 12:38:29 AM at epicenter=20 Time of Earthquake in other Time = Zones
Locati= on	38.483=B0N, 87.857=B0W
Depth=	10 km (6.2 miles) set by location program
Region	ILLINOIS
Dista= nces	11 km (7 miles) NW (315=B0) from Mount Carmel, = IL 12 km (7 miles) NNE (23=B0) from Bellmont, = IL 13 km (8 miles) ENE (72=B0) from Bone Gap, = IL 62 km (39 miles) NNW (335=B0) from Evansville, = IN 208 km (129 miles) E (94=B0) from St. Louis,=20 MO
Loc= ation=20 Uncertainty	horizontal +/- 4.1 km (2.5 miles); depth fixed by location=20 program
Para= meters	NST=3D 95, Nph=3D 95, Dmin=3D34.9 km, Rmss=3D1.36 sec, Gp=3D=20 25=B0, M-type=3Dmoment magnitude (Mw), Version=3D8
Source	USGS NEIC (WDCS-D)
Event=20 ID	us2008rcar