Powerful M7.8 Earthquake Strikes Iran-Pakistan Border: AIR Analysis

April 17, 2013

Catastrophe modeling firm AIR Worldwide has issued a report on the powerful M7.8 earthquake, which struck a sparsely populated area of southeastern Iran about 50 kilometers (30 miles) from the country’s border with Pakistan, just after 3:00 p.m. local time (10:44 UTC) on April 16.

The United States Geological Survey (USGS) reported that the earthquake “struck at a depth of 82 kilometers (51 miles). The Iranian Seismological Center characterized the quake as the worst to strike the country in 40 years. It was felt as far away as New Delhi, India, and the Gulf States.” According to AIR, however, “insurance losses from this event are expected to be minimal.”

AIR described the geological forces involved. It said: “Four major tectonic plates (the Arabian, Eurasian, Indian, and African plates) and one smaller tectonic block (Anatolia) are the source of the seismicity and tectonics in the Middle East and its immediate surrounding regions.

“In southern Iran, seismic activity is dominated by the collisions of the Arabian and Indian plates with the Eurasian plate. At the longitude of today’s event, the Arabian plate is converging toward the north-northeast at a rate of approximately 37 millimeters [1.443 inches] a year with respect to the Eurasian plate.

“The M7.8 rupture today occurred as a result of normal faulting at an intermediate depth— about 82 kilometers (51 miles)—in the Arabian plate lithosphere (the uppermost region of the earth’s crust). The Arabian plate is subducting (pushing beneath) the Eurasian plate at the Makran coast of Pakistan and Iran south of today’s event.”

AIR also explained that the “subducting Arabian plate is known to be seismically active to depths of about 160 km [100 miles]. The frequency of moderate and large earthquakes within the Arabian plate is not high compared to similar activity in other subducted plates worldwide, but several earthquakes have occurred within this slab in the region of today’s event over the past 40 years, including a magnitude 6.7 shock 50 km to the south in 1983. In January 2011, an M7.2 earthquake occurred approximately 200 km [125 miles] to the east (in Pakistan), where the tectonic environment is similar to that of today’s event.

“In Saravan (population 60,000), the largest Iranian city close to the epicenter of the earthquake, a state of emergency was declared. A Saravan official reported that about six or seven people had been injured and that buildings were damaged in villages near Saravan and near Khash, a smaller town closer to the epicenter. In Zahedan (population 550,000), northwest of the epicenter, people reportedly poured into the streets when the shaking began.”

The latest news reports available indicate that there have been at least 30 deaths in Pakistan and more than 150 injuries. Reports from Iran have yet to mention any deaths, but have said at least 27 people have been injured.

In Pakistan, officials reported injuries in the town of Mashkeel in the province of Baluchistan, which borders the Iranian province where the earthquake ruptured. AIR reported that officials in Pakistan said “that several hundred houses in the town had collapsed. In Karachi, about 700 km (435 miles) to the east, news reports showed buildings shaking and people running from them in panic. Other reports state that the walls of residential buildings and government offices developed cracks from the shaking.”

The earthquake caused tall buildings to shake and sway as far away as India’s capital, New Delhi (1,500 km/950 miles distant), also sending people running into the streets. Buildings in Qatar and Dubai were also reported to have been evacuated because of shaking.

According to AIR, “Iran is situated on major geological fault lines, and earthquakes are not uncommon in the country. Only one week ago, on April 9, an M6.3 quake struck close to Iran’s only nuclear power station—on the opposite (western) side of the country.”

Source: AIR Worldwide and news reports

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