Charleston Earthquake 1886: Date, Magnitude, Epicenter

The Charleston earthquake struck at about 9:50 on the night of Tuesday, August 31, 1886, and lasted less than a minute. Modern estimates put it between magnitude 6.9 and 7.3, which makes it the largest earthquake ever recorded in the southeastern United States, and its center was not in Charleston. It was in Dorchester County, near Summerville and Middleton Place, about twenty-five kilometers up the Ashley River.

When was the Charleston earthquake, and how big was it?

August 31, 1886, in the middle of a heat wave. The U.S. Geological Survey’s seismic network in South Carolina gives the time as about 9:50 p.m.; other accounts say 9:51. Nobody had instruments close enough to measure it, so the magnitude is reconstructed from damage and from how far away people felt it. Wikipedia’s summary of the research gives a range of 6.9 to 7.3. The Post and Courier, citing the USGS, calls it roughly magnitude 7. Either way, nothing in the historical record of the Southeast comes close. The state’s second-largest recorded quake, at Union in 1913, was a 5.5.

The shaking was felt in Boston, Chicago, Milwaukee, and New Orleans, and across the water in Cuba and Bermuda. One estimate puts the felt area at more than five million square kilometers.

Where was the epicenter?

Upriver. Eleven days after the shock, a USGS geologist named Hayden published a map in Science placing the center about twenty-five kilometers northwest of Charleston. The South Carolina Seismic Network describes the zone of greatest damage as an ellipse roughly twenty by thirty miles, running northeast between Charleston and Jedburg, taking in Summerville, and centered roughly at Middleton Place. The USGS now calls the buried fault system there the Middleton Place-Summerville Seismic Zone.

What that meant on the ground: along the South Carolina Railroad at Summerville the earth rose about a meter. Southeast of town, researchers later measured a right-lateral offset of about four and a half meters in the track; witnesses said the rail bed had been “forced to the right.” A fissure more than six hundred meters long opened about forty kilometers from the city. Tracks snapped and trains left the rails, including a locomotive on Ten Mile Hill. Dams broke and flooded farms. Telegraph wires went down and the region went silent for the outside world.

The Old White Meeting House on Dorchester Road, a brick church first built around 1700 by the Congregationalists who founded the town of Dorchester, was reduced to ruins. At Middleton Place the walls of the main house and the north flanker, already burned by Union troops in 1865, came down. At Drayton Hall the laundry house was destroyed.

What were the sand blows?

The coastal plain here is loose, wet sediment on top of old rock. When it shook, the sediment liquefied. Water and sand shot up through cracks in the ground and left small cones that look like miniature volcanoes. The USGS calls them sand blows; the 1886 accounts call them craterlets. They appeared across the countryside between Charleston and Summerville, and they are the reason geologists can date earthquakes that happened before anyone was here to write them down. Buried sand blows in the coastal sediments point to seven large prehistoric earthquakes in this zone, four of them in the last two thousand years.

How many people died, and what did it destroy?

At least sixty people died. Counts vary; some accounts say about a hundred. Property damage was put at five to six million dollars in 1886 money. About two thousand buildings across the Southeast were damaged, and nearly every one of Charleston’s roughly eight thousand structures had cracked plaster or broken glass. Brick buildings took eighty-one percent of the structural damage. Wood-frame houses on filled or “made” ground were damaged at a rate of fourteen percent; on solid ground the rate was half of one percent. Tybee Island, Georgia, more than sixty miles away, had major damage. Savannah, Augusta, and Columbia were hit.

In Charleston the Old City Jail lost its octagonal tower and top story. The top of the Unitarian Church’s tower fell through the roof into the nave. Both were rebuilt lower.

What are the earthquake bolts on Charleston houses?

After the quake, owners of unreinforced brick buildings ran long iron rods through their houses, wall to wall, and tightened them with plates and nuts on the outside to pull the walls back together. The practice was already known in the city as a defense against hurricanes. The exterior plates, called gib plates or washer plates, were often cast in decorative shapes, and today they are pointed out on nearly every walking tour of the peninsula. They are the one part of the earthquake the tours remember.

How long did the aftershocks last?

The first came about ten minutes after the main shock. At least seven more were felt in the next twenty-four hours. Of 435 or more earthquakes recorded in South Carolina between 1754 and 1975, more than three hundred were aftershocks in the thirty-five years after 1886. The USGS report on the disaster, compiled by Clarence E. Dutton from the field work of McGee and Hayden and published in the survey’s 1887-88 annual report, ran 325 pages and remains the definitive account. Dutton used the arrival times to estimate how fast seismic waves travel, and introduced a method for estimating an earthquake’s depth from the pattern of shaking.

The ground near Summerville has not stopped. The USGS seismic network says low-level activity continues in the same area today, and some researchers consider the small quakes that still rattle Dorchester County, 134 of them in 2011 and 2012 alone, to be the tail end of the 1886 sequence. The question of whether the fault is still active is its own page.

Is there anything left to see?

The Old White Meeting House ruins and cemetery are on Dorchester Road in Summerville and are on the National Register. The ruins at Colonial Dorchester State Historic Site, once part of the same settlement, predate the quake but stand on the same ground. The earthquake bolts are all over the peninsula.

The rest is in the dispatches. The county map at /map/ marks the railroad and the meeting house. The county history at /history/ follows what the earthquake did to Summerville. And the story at /whatever-hour-it-strikes/ concerns a town clock on a brick tower, a little north of the ellipse. The clock keeps good time. That is the official position of the town, and it is nearly always true.

The 1886 Charleston Earthquake, From the Epicenter Out