Behind the April 5th Earthquake And Other Earthquakes

In the morning of April 5, 2024, U.S. states along the East Coast were shaken by an earthquake centered in New Jersey at a moderate magnitude. Learn more about the causes of earthquakes like this and how to prepare for an earthquake!

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By Ruiqi He

A 15-second magnitude 4.8 earthquake centered in New Jersey shook the surrounding Northeastern states of New York, Connecticut, Pennsylvania, and Maryland on April 5 at 10:23 a.m. Many Stuyvesant students were startled by the sudden shaking of the largest earthquake in North Jersey since 1884. People also felt vibrations from a 3.8 magnitude aftershock at 5:30 p.m. on the same day. Residents on the East Coast are expected to experience aftershocks within the next week or even the next month with each subsequent aftershock being lower in magnitude. Thankfully, there was no significant danger to infrastructure or severe injuries.

Earthquakes are the shaking of Earth’s surface which generally occur when there is a sudden slip between tectonic plates. Tectonic plates, large slabs of rock within the crust (including both continental and oceanic crust), are constantly moving due to the convection currents—rising and sinking of gas and molten metal in the mantle—below the crust in the mantle. However, most of Earth’s 15 tectonic plates move at a rate of 1.5 centimeters per year due to friction between the plates’ edges. Once the stress generated by friction overcomes the force of friction, energy is released in motion waves (seismic waves) that traverse the Earth’s crust. This vibration contributes to the shaking felt during earthquakes. Earthquakes can also trigger other natural disasters like landslides, avalanches, and tsunamis as the disturbance of Earth’s crust directly causes the disturbances of soil, snow, and water above the crust. 

Since New Jersey is not located along any plate boundary, many wonder how an earthquake could have occurred there. The April 5 earthquake had a special cause—ancient faults, or crust fractures, which extend through the Appalachian Mountains to New England, New York, New Jersey, and Philadelphia. The April 5 earthquake originated from an unnamed fault in Lebanon, New Jersey. Unlike areas near active plate boundaries, the Northeastern United States don’t have fault lines, but instead, cracks and weaknesses have accumulated within the crust over thousands of years. Due to gravity, when rock on either side of the fracture eventually slips, the nearby ground shakes, thereby producing an earthquake. 

The magnitude of earthquakes was originally determined by the Richter scale, proposed in 1935 by Charles F. Richter and Beno Gutenberg. The scale is logarithmic (increasing by one on the scale is an increase by a factor of 10). Generally speaking, earthquakes scaled one to three are considered minor, four to six are considered moderate, seven to eight are considered strong, and nine to 10 are considered extraordinarily strong. An earthquake is measured using a seismograph, an instrument that records the ground motion of the earthquake in the form of a graph. A simple seismograph consists of a pen attached to a weight hanging on a spring. Since the weight is sensitive to motions of the Earth, as the weight moves, the pen also moves and draws a graph recording ground motion. After obtaining the recording, the common logarithm of the amplitude of the biggest wave is taken as the earthquake’s magnitude. Though the Richter Scale is largely accepted as an accurate measure of an earthquake’s power, its main drawback is that it was originally intended to measure earthquakes with large differences in magnitude. Today, most seismologists use other similar scales that are able to detect more subtle differences in magnitude.

Although northeastern states aren’t located along any plate boundaries, some residents fear of having more, perhaps even stronger, earthquakes following the April 5 earthquake. However, states like these have already experienced frequent, low-magnitude earthquakes. Since 1700, the northeast has experienced over 2000 quakes. For example, in January 2024, there was a magnitude 1.7 earthquake near Astoria, Queens, New York City. There is no way to predict when earthquakes will occur, but other environmental factors can increase the frequency of earthquakes in the northeast. Extensive flooding can lead to potential landslides due to increased soil erosion, resulting in quakes. Furthermore, rising sea levels resulting from climate change increase the pressure exerted on Earth’s coastlines, thereby increasing the frequency of earthquakes. 

Luckily, for states along the East Coast like New York, moderate to severe earthquakes are rare. However, it is still important and safe to be well acquainted with the safety guidelines and emergency preparedness for earthquakes. The California Earthquake Authority recommends preparing a survival kit and having an emergency preparedness plan ready. Your survival kit should include at least three days’ water (one gallon per person per day), nonperishable (canned) food for each member of your family, a can-opener, first-aid kits, prescription medications, flashlights with additional batteries, a whistle, duct tape, maps, power packs for phones, a knife for opening objects, a few bills of cash, and important documents sealed in water-proof holders. Additionally, minimize the destruction of your home before a potential earthquake by securing tall bookshelves, safely storing flammable liquids, placing fragile objects on the highest shelves, securing heavy picture frames, and installing latches on cabinets to prevent them from opening when shaken. During an actual earthquake, drop, cover, and hold on. First, no matter where you are, drop on your knees and hands to easily crawl to the nearest shelter. Cover your head and neck with one arm while using the other arm to crawl under a nearby desk or interior wall far away from windows. Then, hold onto a sturdy object like a table leg with one hand with the other hand still covering your head and neck.
Nevertheless, many people living along the East Coast experienced their first moderately severe earthquake on April 5. Earthquakes on a smaller scale in this region are more common than they appear, but there is no significant risk to infrastructure or public safety. However, it is always important to know how to react in the case of a mild to strong earthquake.