This has been a busy week, seismically-speaking.
On Tuesday, October 15th, the heavily-faulted Philippines experienced the largest quake of the week, clocking in at magnitude 7.1. The earthquake was at a location 2 km east of Catigbian. There are reports of deaths and significant property damage due to the Philippine earthquake.
In addition Crete, Greece experienced a M6.4 quake 30 km west of Platanos, and Panguna, Papua New Guinea experienced a M6.8 quake.
The United States Geological Survey’s real time earthquake map showed 1564 earthquakes (all magnitudes in the US and its territories and at least M4.0 elsewhere) of which 104 were ≥M4.5. The majority of the rest of the tremors this week occurred around the complex boundary between the Pacific and Australian tectonic plates in the western Pacific.
The Week’s Largest Earthquake: M7.1, Catigbian, Philippines
News reports suggest that there are at least 99 people dead and 276 more injured due to the Philippine earthquake, with most of the deaths and injuries in Bohol province. The Bohol Region of the Philippines is close to three types of major tectonic boundaries: Subduction, ridges, and transformation faults. As such , it is one of the more seismically active areas of the country. Tuesday’s quake was the result of shallow reverse faulting on a moderately inclined fault, dipping either to the northwest, or to the southeast.
Most of those killed were hit by falling rubble, with reports of landslides in Cebu as well. The quake was centered about 620 kilometers (385 miles) south-southeast of Manila, near Catigbian, and its depth was 20 kilometers (12 miles), according to the U.S. Geological Survey.
The Week’s Mediterranean Earthquake: M6.8, Crete, Greece
The U.S. Geological Survey reported the center of the quake, at 9.11 a.m. ET, was 22.5 miles below the seabed, and 43 miles west of Chania on Crete. The Athens Geological Institute further reported that tremors were felt as far as the Greek capital Athens, some 180 miles away, and across southern Greece including the Peloponnese peninsula and the Cyclades cluster of islands.
Although the Institute reported the tremor at M6.2, which is under The USGS’s M6.8 rating, the Athens Institute nevertheless described the quake as severe. Fortunately, there was little damage from this event, probably because of the depth.
Greece is often rocked by earthquakes – most of which cause no serious damage. An M5.9 quake in 1999, however, killed 143 people.
U.S. Earthquakes: California
California was not exempt from this week’s quakes; the Northern California Seismic System, UC Berkeley and USGS Menlo Park reported an M4.9 earthquake 52km WNW of Eureka, California at a depth of 6.1 miles.
The month so far has illustrated the variability in our planet’s seismic activity. From the devastating Philippine earthquake to a over 6M quake in Greece, this week’s quakes offer insight into the never-ending movement of our Earth.
Mungin, Lateef. Dozens dead as magnitude-7.1 earthquake hits the Philippines. (2013). Accessed October 16, 2013
Koutantou, Angeliki and Tagaris, Karolina. Quake of 6.4 magnitude causes minor damage on Crete. (2013) Accessed October 16, 2013
USGS. Real time earthquake map. Accessed October 16, 2013