Arab News Japan

TOKYO: The Earthquake Research Institute at the University of Tokyo has analyzed the recent earthquakes in Turkey and said the occurrence of two similarly large quakes was rare.

The Institute also pointed out that different monitoring organizations came up with different results for the two quakes.

The first quake took place at 4:17 local time and registered 7.8 at a depth of 17.9 km by the United States Geological Survey (USGS). Columbia University’s Global Centroid-Moment-Tensor (CMT) also registered 7.8 on the Richter Scale but calculated the depth at 14.9 km, while Turkey’s Disaster and Emergency Management Authority (AFAD) saw the magnitude at 7.7 but at a shallower depth of just 8.6 km.

The second quake occurred at 13.24 and registered 7.5 at a depth of 10 km (USGS), 7.7 at 12 km (Global CMT) and 7.6 at 7 km (AFAD).

The Institute said that for both the M7.8 and M7.5 earthquakes, strong ground motions with large acceleration, velocity and displacement were observed over a wide area along the fault, adding, “Due to the magnitude of the earthquake, it is thought that a fairly wide area was suffered by strong shaking.”

In its report, the Institute stated: “The M7.8 earthquake in Turkey occurred mainly northeast of the epicenter along the earthquake gap that had been pointed out since the Great Earthquake of 1513 along the East Anatolian Fault Zone.”

“Judging from the USGS epicenter location and past active fault maps, the rupture started on a northwest-dipping normal fault (Narli fault) and transferred to the East Anatolian fault. After that, it is believed that the main rupture occurred in the northeast direction.”

“The M7.5 earthquake is thought to have been ruptured mainly by the Cardak Fault (formerly known as the Elbistan Fault), an east-west left-lateral strike-slip fault derived from the East Anatolian Fault. Since the epicenter is located near the center of the fault, the rupture is believed to have propagated in both directions. Historical earthquakes (e.g., Ambraseys, 2009) have been confirmed in the vicinity.”