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USGS Response
Overview
A magnitude 5.9 earthquake struck near Khōst, Afghanistan on June 22, 2022 at 1:24 am local time (June 21 20:54 UTC). Seismic instrument data indicate the earthquake originated at a depth of 6.2 miles (10 kilometers).
The earthquake struck about 29 miles southwest of Khōst. Perceived shaking for the quake was violent. The USGS PAGER report shows RED for shaking-related fatalities and ORANGE for economic losses – indicating high casualties and widespread damage. News outlets are reporting over 1,000 fatalities.
The earthquake struck at a shallow depth in a region with buildings extremely vulnerable to earthquake shaking. The event occurred due to strike-slip faulting in the plate boundary zone between the Eurasia and India plates. The left-lateral, strike-slip Chaman fault is the fastest moving fault in the region and has caused large and destructive earthquakes in the past. Moderate magnitude earthquakes like the June 21 earthquake are relatively common in this region. The USGS National Earthquake Information Center (NEIC) has located two aftershocks of this earthquake – an M4.5 on June 21 (approximately 1 hour after the M5.9 mainshock), and an M4.3 on June 24. There are likely many more aftershocks of smaller magnitudes than these two that have not been located by the NEIC owing to a lack of seismic stations in the region that would be necessary to detect and locate smaller magnitude earthquakes. Aftershocks that have not been detected and located by the NEIC may still be felt by people in the immediate vicinity of the aftershock.
Visit the USGS earthquake event page for more information. For estimates of casualties and damage, visit the USGS Prompt Assessment of Global Earthquakes for Response (PAGER) website.
Tectonic Summary
Earthquakes and active faults in eastern Afghanistan and western and northern Pakistan are the result of the India plate moving northward at a rate of about 40 mm/yr (1.6 inches/yr) and colliding with the Eurasia plate. Along the northern edge of the Indian subcontinent, the India plate is subducting beneath the Eurasia plate, causing uplift that produces the highest mountain peaks in the world, including the Himalayan, the Karakoram, the Pamir and the Hindu Kush ranges. West and south of the Himalayan front, the relative motion between the two plates is oblique, which results in strike-slip, reverse-slip, and oblique-slip earthquakes.
In the vicinity of south-eastern Afghanistan and western Pakistan, the India plate translates obliquely relative to the Eurasia plate, resulting in a complex fold-and-thrust belt south of the Chaman fault. Faulting in this region includes strike-slip, reverse-slip and oblique-slip motion and often results in shallow, destructive earthquakes. The active, left-lateral, strike-slip Chaman fault is the fastest moving fault in the region.
The generalized terranes that make up Afghanistan are distinctly related to the Hari Rod and Chaman faults. The June 21, 2022, M5.9 earthquake occurred within the broader deformational region south of the Chaman fault zone that defines the western strike-slip boundary between the India and Eurasia plates, and approximately 100 km east of the Chaman fault itself. The Chaman fault is a major left-lateral strike slip fault along the Pakistan-Afghanistan border that exhibits tectonic slip rates similar to the San Andreas fault in California.
Large (M7+) earthquakes along the Chaman fault are rare, if present at all, due to extensive aseismic creeping segments, and earthquakes with magnitudes similar to the M5.9 June 21, 2022, earthquake are relatively common along the Chaman fault and within the deformational belt south of the Chaman fault. Although the Chaman fault rarely produces large earthquakes, the relative plate motion between the India and Eurasia plates is partitioned onto additional faults within the Chaman fault system, and these faults have produced M7+ earthquakes as recently as 1935.
Twelve additional earthquakes of magnitude 5.5 or larger, including four earthquakes of magnitude 6.0 and larger, have occurred within 250 km of the June 2022 earthquake since 1960. The June 21, 2022, earthquake is about 500km (300 miles) north-northeast of a deadly magnitude 6.4 earthquake that occurred on October 10th 2008 in western Pakistan that killed 166 people and destroyed several villages from triggered landslides.
Ground Failure
Landslides triggered by the M5.9 earthquake were estimated to be significant in number and/or spatial extent (see link here). The number of people living near areas that could have produced landslides in this earthquake is limited. This is not a direct estimate of landslide fatalities or losses and was determined based on results modeled using the USGS ShakeMap product.
There can be significant, localized noise from rockfall events, such as rocks rolling, tumbling, and(or) falling down slopes. Reports of “bangs of huge stones falling down” is an expected result of rockfall events, as is dust and, if near the event, the sensation of the ground shaking like a passing train or semitruck. Initial interpretation of limited satellite imagery for the area impacted by the earthquake does not reveal evidence of significant landslides or rockfall. However, small landslides and rockfall may not be visible due to the resolution of available imagery.
Aftershocks
Most large earthquakes are followed by additional earthquakes, called aftershocks, which make up an aftershock sequence. While most aftershocks are smaller than the mainshock, they can still be damaging or deadly. In a small fraction of sequences, an aftershock can occur that is larger than the first earthquake, in which case the first earthquake is referred to as a foreshock.
Predicting the exact time, location, and magnitude of an aftershock remains impossible, but the USGS does calculate the probabilities and expected numbers of earthquakes within the aftershock sequence, in what are referred to as operational aftershock forecasts. The USGS only issues public aftershock forecasts for domestic earthquakes in the United States and its territories, but earthquake behavior is similar around the world, and an earthquake of M5.9 can be expected to have several aftershocks larger than magnitude 4, and dozens of smaller aftershocks that could be felt in the region.
Earthquake Detection
The USGS National Earthquake Information Center has detected and cataloged at least two aftershocks larger than Magnitude 4 in the first week of the sequence. Many smaller aftershocks are likely to have occurred but may be absent from the seismic catalogs due to a lack of local stations. These smaller aftershocks may still be felt by people close to the epicenters.