The science of earthquakes
When it comes to natural or “weather-related hazards”, in Missouri, we think of thunderstorms, floods, and tornadoes. But there is one that is less common and lies beneath the surface—earthquakes.
The root cause of earthquakes is geographic features called faults, or fault lines, defined as a fracture between two blocks of rock. Faults range in length from less than a foot to thousands of miles, and are categorized into three common types: normal, reverse, and strike-slip.
In a normal fault, the crust stretches and one block slips down. During a reverse fault, the upper block moves up and over the lower block. Then, in a strike-slip fault, blocks slide past each other horizontally.
The Ring of Fire, which extends from the west coast of North America to the east coast of Japan and Indonesia, is the Earth’s most active seismic zone. This seismically active zone runs along a series of faults that surround the Pacific tectonic plate.
While not as active as the “Ring of Fire”, a more local fault line has also been known to produce sizable earthquakes across parts of the Midwest and Mid-South.
The New Madrid fault lies within the Bootheel of Missouri and extends through northeastern Arkansas, western Tennessee, and parts of Kentucky and Illinois.
The largest and most impactful New Madrid earthquake events occurred in the early 1800s, when four different earthquakes struck in the winter of 1811 - 1812. Each has a magnitude between 7.0 and 8.0, but what do those numbers actually mean?
Geologists use instruments called seismographs to detect and record the intensity of seismic events. Earthquake strength is measured using the Richter scale, which ranges from 1 to 10.
A magnitude 10 is the highest on the scale, and has yet to be achieved on Earth. Earthquakes with a magnitude over 7 are considered major and often result in considerable to significant damage to structures, depending on their integrity.
If an earthquake strikes, stay indoors and cover your head and neck with your arms or a pillow, and get underneath something sturdy. If you are outdoors, move to an open area away from buildings and trees, then drop and cover until the ground stops shaking.
