A New Natural Disaster: Earthquake in Islamabad
An earthquake struck Islamabad with an epicenter located 95 kilometers northeast of the city, registering a magnitude of 7.6 on the Richter scale. This disaster devastated a vast region across Pakistan, Afghanistan, and India, resulting in tens of thousands of deaths and missing persons.
The earthquake’s epicenter lies within the collision zone between the Indian-Australian plate and the Eurasian plate, situated in the upper reaches of the Indus River, where the two major mountain ranges—the Hindu Kush and Karakoram, reaching heights of 28,250 feet (8,475 meters), and the Himalayas, standing at 29,028 feet (8,710 meters)—meet.
Why is it that in Asia, no decade passes without an earthquake? Recently, devastating earthquakes have occurred in regions such as Iran, Turkey, and Indonesia. The primary cause of these seismic events is the ongoing collision between tectonic plates. One plate subducts beneath another, leading to the formation of mountain ranges like the Hindu Kush, Karakoram, and Himalayas.
At varying depths (from the surface to the Earth’s core), the Earth is differentiated into several layers. The outermost layer is the Earth’s crust, averaging 40 kilometers in thickness, followed by the upper mantle, which extends from 40 kilometers to 900 kilometers deep. Within this region, the process of differentiation occurs, involving the movement of layers: the lithosphere, comprising the Earth’s crust and the rigid part of the upper mantle, averages around 120 kilometers in depth, while the asthenosphere extends from 120 kilometers to 700 kilometers deep. The components of the lithosphere move in different directions and are segmented into distinct entities known as tectonic plates, which drift on the asthenosphere.
In South Asia and Southeast Asia, the boundaries where three plates meet are developing: the Eurasian plate, the Indian-Australian plate, and the Pacific plate (see diagram), with two types of boundaries: subduction zones and collision zones. At these contact boundaries, a portion of one plate subducts beneath another, causing intense compressive forces. When these forces reach a critical threshold, they can lead to earthquakes, volcanic eruptions, tsunamis, and other geological phenomena. The depth of earthquake epicenters can range from 60-70 kilometers to 100-120 kilometers.
The earthquakes in South Asia and Southeast Asia are governed by this collision and subduction process. Significant earthquakes have occurred and will continue to occur in South Asia. Data measuring the collision velocities of these plates indicate a growing likelihood of strong seismic activity, with no signs of cessation.
In recent decades, the intensity of earthquakes suggests that the seismic zone in Southwest Asia (the Hindu Kush region) is more powerful than the eastern zone (the Himalayas).
As illustrated, Vietnam is fortunate to have a “safe” distance from the tectonic structures that could generate strong earthquakes. However, this does not mean that earthquakes do not occur within Vietnam’s territory and maritime areas. In fact, a long list of earthquakes has been recorded throughout history and continues to occur today. Nevertheless, these earthquakes happen through a different mechanism and are of significantly lesser magnitude, typically with epicenters at depths of around 18-30 kilometers.
To date, scientific data provide no basis to suggest that Vietnam will experience strong earthquakes or tsunamis similar to those occurring in the aforementioned collision and subduction zones.
Dr. Phan Van Quynh, Hoang Huu Hiep
