Seismotectonic aspects of the 2025 Kunar, Afghanistan, earthquake using field observations, InSAR and optical imagery
This study characterizes the seismotectonic aspects of the 31 August 2025 Mw 6.0 Kunar, Afghanistan earthquake, which caused significant damage and landslides via thrust faulting on the Kunar fault system, by integrating field observations with InSAR and optical imagery to reveal a complex, heterogeneous mainshock deformation field distinct from the more compact aftershock pattern.
Original paper licensed under CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). This is an AI-generated explanation of the paper below. It is not written or endorsed by the authors. For technical accuracy, refer to the original paper. Read full disclaimer
The ground beneath our feet is not a static, unchanging slab of rock. It is a dynamic surface shaped by the slow, relentless collision of massive tectonic plates that make up the Earth's crust. In regions where these plates crash into one another, the crust crumples, folds, and breaks, creating mountain ranges and storing immense energy. When that stored energy is suddenly released, it travels through the ground as seismic waves, causing the violent shaking we call an earthquake. While scientists can map the major fault lines where these breaks usually happen, the Earth's crust is also full of smaller, hidden fractures. These secondary faults can remain quiet for decades or even centuries, accumulating stress until they finally slip, often in remote, rugged terrain where their presence is difficult to detect until disaster strikes. Understanding exactly how these hidden faults move and how the ground deforms during an earthquake is critical, not just for mapping the Earth's history, but for protecting the communities living in these volatile zones.
On August 31, 2025, a shallow earthquake of magnitude 6.0 struck the Kunar Province in eastern Afghanistan, a region defined by steep, high-relief mountains and deep valleys. The tremor, centered in the Nurgal District, was powerful enough to shatter the unreinforced mudbrick and stone homes that many locals call home, triggering a cascade of over 104 landslides that buried roads and villages. In the aftermath, a researcher led by Zakeria Shnizai from the University of Oxford set out to understand the mechanics of this event. They combined direct field observations with advanced satellite technology to peer through the clouds and map the invisible shifts in the Earth's surface. Their goal was to determine exactly which fault broke, how the ground moved, and why the damage was so severe in specific areas.
The researcher found that the earthquake was caused by thrust faulting, a type of movement where one block of rock is pushed up and over another, occurring on the northern segment of the Kunar fault system. This fault system is part of a larger, complex zone of deformation where the ground is being squeezed and twisted. While the main fault in the region is known for sliding sideways, the specific rupture that caused this disaster involved smaller, subsidiary faults that push the ground upward. They used satellite radar, a technique that can measure ground movement with centimeter-level precision, to create a detailed picture of the deformation. They discovered that the main earthquake created a broad, uneven area of uplift covering roughly 12 kilometers by 9 kilometers, with the ground rising by as much as 22 centimeters in some spots. This complex pattern suggests that the earthquake did not break along a single, clean line, but rather involved multiple strands of the fault system breaking in a staggered sequence.
A few days later, on September 4, a significant aftershock of magnitude 5.6 occurred. The satellite data revealed a striking difference in how this second event moved the ground. Unlike the mainshock, which produced a messy, widespread deformation field, the aftershock created a compact, oval-shaped zone of uplift about 5 kilometers by 9 kilometers. This smaller, more focused movement was centered slightly to the west of the main event and reached a peak displacement of 15 centimeters. The shape and location of this deformation suggest it happened on a single, moderate-sized fault structure. The fact that the two events moved the ground in different ways and in slightly different locations indicates that the stress from the first earthquake triggered a secondary rupture on a neighboring part of the fault system, a process known as cascading rupture.
The human cost of this geological event was devastating, with over 2,200 fatalities and thousands more injured. The researcher noted that the severity of the tragedy was not solely due to the strength of the shaking, but also to the vulnerability of the local infrastructure. Most homes in the affected villages were built from mud and stone without steel reinforcement, and many were stacked on steep, unstable slopes. When the ground shook, these structures collapsed easily. Furthermore, the heavy rains that had soaked the hillsides in the days before the earthquake weakened the soil, making the mountains particularly prone to sliding. The combination of seismic shaking and saturated ground turned the event into a multi-hazard disaster, where landslides blocked access to remote villages and buried homes under tons of rock and debris.
By mapping the surface cracks, landslides, and the precise movement of the ground, the study highlights a crucial reality for seismic hazard in this region. The earthquake did not occur on a major, well-known fault that had been carefully monitored for years. Instead, it ruptured a smaller, less obvious fault strand within a complex mountain range. This finding suggests that in areas with steep topography and rapid erosion, dangerous earthquakes can happen on faults that leave very few visible traces on the surface until they break. The research underscores that the seismic risk in eastern Afghanistan is driven by a network of these hidden, secondary faults, which can accumulate enough stress to cause catastrophic damage despite their lack of a prominent surface expression. The work serves as a stark reminder that in the high mountains of the Hindu Kush, the Earth's movement is complex, and the ground beneath even the most remote villages can shift in ways that are difficult to predict until the moment of rupture.
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