The Earthquake of 2011 EarthCache
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Today we are going to learn about Earthquakes!
Part of the fun of this Earth cache is reading where everyone was in their logs. So enjoy the posts below! Some great stories!
On Tuesday, August 23, 2011 at 01:51:04 PM, EST, Virginia was shaken with a 5.8 magnitude earthquake.
geological fault - (geology) a crack in the earth's crust resulting from the displacement of one side with respect to the other; "they built it right over a geological fault"; "he studied the faulting of the earth's crust"
Felt Reports
Moderately heavy damage (VIII) occurred in a rural region of Louisa County southwest of Mineral. Widespread light to moderate damage occurred from central Virginia to southern Maryland including the Washington D.C. area. Minor damage reported in parts of Delaware, southeastern Pennsylvania and southern New Jersey. Very strongly felt (VII) at Boston, Bumpass, Kent Store, Louisa, Mineral, Rhoadsville and Summerduck. Felt strongly in much of central Virginia and southern Maryland. Felt throughout the eastern US from central Georgia to central Maine and west to Detroit, Michigan and Chicago, Illinois. Felt in many parts of southeastern Canada from Montreal to Windsor.
Tectonic Summary
The Virginia earthquake of 2011 August 23 occurred as reverse faulting on a north or northeast-striking plane within a previously recognized seismic zone, the "Central Virginia Seismic Zone." The Central Virginia Seismic Zone has produced small and moderate earthquakes since at least the 18th century. The previous largest historical shock from the Central Virginia Seismic Zone occurred in 1875. The 1875 shock occurred before the invention of effective seismographs, but the felt area of the shock suggests that it had a magnitude of about 4.8. The 1875 earthquake shook bricks from chimneys, broke plaster and windows, and overturned furniture at several locations. A magnitude 4.5 earthquake on 2003, December 9, also produced minor damage.
Previous seismicity in the Central Virginia Seismic Zone has not been causally associated with mapped geologic faults. Previous, smaller, instrumentally recorded earthquakes from the Central Virginia Seismic Zone have had shallow focal depths (average depth about 8 km). They have had diverse focal mechanisms and have occurred over an area with length and width of about 120 km, rather than being aligned in a pattern that might suggest that they occurred on a single causative fault. Individual earthquakes within the Central Virginia Seismic Zone occur as the result of slip on faults that are much smaller than the overall dimensions of the zone. The dimensions of the individual fault that produced the 2011 August 23 earthquake will not be known until longer-term studies are done, but other earthquakes of similar magnitude typically involve slippage along fault segments that are 5 - 15 km long.
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 100 km (60 mi) 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 500 km (300 mi) from where it occurred, and sometimes causes damage as far away as 40 km (25 mi).
| Magnitude |
5.8 |
| Date-Time |
- Tuesday, August 23, 2011 at 17:51:04 UTC
- Tuesday, August 23, 2011 at 01:51:04 PM at epicenter
|
| Location |
37.936°N, 77.933°W |
| Depth |
6 km (3.7 miles) |
| <>Region<> |
VIRGINIA |
| Distances |
- 8 km (5 miles) SSW (195°) from Mineral, VA
- 11 km (7 miles) SSE (148°) from Louisa, VA
- 29 km (18 miles) NE (45°) from Columbia,VA
- 61 km (38 miles) NW (317°) from Richmond,VA
- 135 km (84 miles) SW (217°) from Washington,DC
|
Location
Uncertainty |
horizontal +/- 2.3 km (1.4 miles); depth +/- 3.1 km (1.9
miles) |
|
NST= 22, Nph= 23, Dmin=50 km, Rmss=0.44 sec, Gp=
79°,M-type=centroid moment magnitude (Mw), Version=B |
|
|
| Event ID |
se082311a |
Where you are standing is the epicenter of Virginia's 2011 Earthquake. Look across the field to the east.
This earthquake happened on the Spotsylvania Fault, which runs north south.
The depth of this earthquake was 3.7 miles, which caused it to be felt as far north as Rhode Island. Mineral, VA, 5 miles north of the epicenter, received most of the structural damage.
According to the U.S. Geological Survey, the largest recorded earthquake in Virginia history was a 5.9 on the scale, centered around Giles County in 1897.
The Washington Monument, 81 miles from the epicenter, closed after a crack appeared. As of November, 2011, repairs continue.
December 27th, 2011 update- The Washington Monument will take $15,000,000 to repair. The Feds are giving $7.5 million and the NPS needs to come up with the other half in private donations.
The National Cathedral also suffered.
This shows how far away an epicenter can be and still be felt as strong as it was. If you felt this earthquate, think about how far away you were from here and how much the earth moved. That is a lot of energy being transferred!!!
Maybe you will get lucky to feel one of the many aftershocks continuing in the area.
To log this earthcache, please post answers to the following in your Log (Part of the fun of this cache will be reading about other peoples experiences):
1. Tell where you were when the earthquake took place. What was the distance?
2. Explain how much you felt the quake, if any. Did things move? Fall over? Shake, rattle or roll?
3. By looking at the map of recent earthquakes, what do you think is the likely hood of another major earthquake happening here? Why?
4. Looking across the field, do you see any signs of the fault? If so where? If not, why?
5. How come there is no large crack in the ground like in California's San Andres Fault?
Additional Hints
(Decrypt)
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