A 6.4 earthquake hit Papua New Guinea Tuesday, piggy-backing off the 6.6 quake that rocked the country just last week. The 6.4 earthquake occurred about 20 miles north of Rabaul, a township located on the eastern-most tip of the Papua New Guinea island cluster.
So far, there have been no reports of any major damage in the country, the Christian Science Monitor reports. Luckily, the 6.4 earthquake did not create a tsunami, a possibility that had residents of Hawaii on edge.
Two simultaneous big quakes near Papua New Guinea in just over a week? What’s the reason for New Guinea’s frequent seismic activity?
Measuring An Earthquake
The magnitude of an earthquake, like the 6.4 earthquake that hit Papua New Guinea Tuesday, is measured on the Richter scale. Developed in 1934 by Charles Richter, the scale goes from 1 to 10, Earthquakes are assigned a number between 1 and 10, with an exponential numerical increase correlating to a ten-fold increase in seismic activity, according to the Michigan Technological University, or MTU. For instance, a 5.0 quake has seismic waves ten times as wide as a 4.0 quake, with an exponentially greater increase in energy released. Pa
According to the Richter scale, a magnitude 2 earthquake is small enough that usually only instruments detect any ground movement. A magnitude 3 quake is felt indoors; an earthquake measuring 5 on the Richter scale is felt by everyone and causes minor to moderate damage; a 6 might see moderate to major damage.
MTU reports that there are an estimated 100 magnitude 6 quakes every year, in addition to approximately 900,000 quakes of magnitude 2.5 or less. That’s about 2,400 small earthquakes every day.
Catastrophic magnitude 8.0 earthquakes, equivalent to detonating 6 million tons of TNT, happen once every five to 10 years. The largest earthquake ever recorded, a magnitude 9.5, occurred in Chile in 1960. According to Encyclopedia Britannica, the quake was so large that tsunami waves 35 feet high reached Hawaii 6,200 miles away, causing millions of dollars in damage at Hilo Bay.
Papua New Guinea: Prime Earthquake Territory
Papua New Guinea, an island nation of roughly 6 million people, lies on a plate boundary known as the Pacific Ring of Fire. It’s the most seismically active region in the world, with about 90 percent of the world’s earthquakes occurring along this ring.
According to the U.S. Geological Survey, since 1900, the New Guinea region has experienced 22 magnitude 7.5+ earthquakes. From the U.S. Geological Survey:
The western end of the Australia-Pacific plate boundary is perhaps the most complex portion of this boundary, extending 2000 km from Indonesia and the Banda Sea to eastern New Guinea. The boundary is dominantly convergent along an arc-continent collision segment spanning the width of New Guinea, but the regions near the edges of the impinging Australia continental margin also include relatively short segments of extensional, strike-slip and convergent deformation. The dominant convergence is accommodated by shortening and uplift across a 250-350 km-wide band of northern New Guinea, as well as by slow southward-verging subduction of the Pacific plate north of New Guinea at the New Guinea trench.
