Find the Mercalli value for the following earthquake. December 16 th , 1811: Nor
ID: 231069 • Letter: F
Question
Find the Mercalli value for the following earthquake.
December 16th, 1811: Northeastern Arkansas (New Madrid Fault): estimated Richter value: 8.0
At the onset of the earthquake the ground rose and fell - bending the trees until their branches intertwined and opening deep cracks in the ground. Landslides swept down the steeper bluffs and hillsides; large areas of land were uplifted; and still larger areas sank and were covered with water that emerged through fissures or craterlets. Huge waves on the Mississippi River overwhelmed many boats and washed others high on the shore. High banks caved and collapsed into the river; sand bars and points of islands gave way; whole islands disappeared. Surface rupturing did not occur, however. The region most seriously affected was characterized by raised or sunken lands, fissures, sinks, sand blows, and large landslides that covered an area of 78,000 - 129,000 square kilometers, extending from Cairo, Illinois, to Memphis, Tennessee, and from Crowleys Ridge to Chickasaw Bluffs, Tennessee.
Although the motion during the first shock was violent at New Madrid, Missouri, it was not as heavy and destructive as that caused by two aftershocks about 6 hours later. Only one life was lost in falling buildings at New Madrid, but chimneys were toppled and log cabins were thrown down as far distant as Cincinnati, Ohio; St. Louis, Missouri; and in many places in Kentucky, Missouri, and Tennessee.
The Lake County uplift, about 50 kilometers long and 23 kilometers wide, upwarps the Mississippi River valley as much as 10 meters in parts of southwest Kentucky, southeast Missouri, and northwest Tennessee. The uplift apparently resulted from vertical movement along several, ancient, subsurface structures; most of this uplift has occurred during earthquakes. The Lake County uplift can be subdivided into several topographic bulges, including Tiptonville dome, Ridgely Ridge, and the south end of Sikeston Ridge. A strong correlation exists between modern seismicity and the uplift, indicating that stresses that produced the uplift still exist today.
Tiptonville dome, which is 14 kilometers in width and about 11 kilometers in length, shows the largest upwarping and the highest topographic relief on the uplift. It is bounded on the east by Reelfoot scarp, which has a zone of normal faults (displacement about 3 meters) at its base. Although most of Tiptonville dome formed between 200 and 2,000 years ago, additional uplifting deformed the northwest and southeast parts of the dome during the earthquakes of 1811-1812.
A notable area of subsidence is Reelfoot Lake in Tennessee, just east of Tiptonville dome. Subsidence there ranged from 1.5 to 6 meters, although larger amounts were reported. It may be that the lake was enlarged by compaction, upwarping, and subsidence occurring simultaneously during the New Madrid earthquakes.
Other areas subsided by as much as 5 meters, although 1.5 to 2.5 meters was more common. Lake St. Francis, in eastern Arkansas, which was formed by subsidence, is 64 kilometers long by 1 kilometer wide. Coal and sand were ejected from fissures in the swamp land adjacent to the St. Francis River, and the water level is reported to have risen there by 8 to 9 meters.
Large waves were generated on the Mississippi River by fissures opening and closing below the surface. Local uplifts of the ground and water waves moving upstream gave the illusion that the river was flowing upstream. Ponds of water also were agitated noticeably. Source: http://earthquake.usgs.gov/regional/states/events/1811-1812.php
What is the Mercalli Value:____________________ ?
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Explanation / Answer
from the intensity and extent of damage it seems that Mercalli value is X or maximum categorised as "extreme".
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