Damage From the Nahrin, Afghanistan, Earthquake of 25 March, 2002
Abstract
On 25 March, 2002, a destructive earthquake of mb = 6.1 struck the city of Nahrin and nearby villages in Baghlan Province in northeastern Afghanistan. The earthquake occurred on a southeast-dipping reverse fault that parallels the linear northeast-trending range front of the Hindu Kush Mountains, east of Nahrin. Field reconnaissance showed no disturbance of the ground by surface rupture, liquefaction, or lateral spreading, and virtually no evidence of landsliding or rockfall. United Nations and Afghan authorities estimate the death toll from the earthquake to be over 2000, with about 20,000 families impacted by the earthquake. We conducted a survey of damage in 68 villages affected by the earthquake and found that areas within 25 km of the epicenter experienced modified Mercalli intensities of between VI and VII. Shaking intensities were strong enough to cause complete building collapse in many villages. Site conditions were an important factor in the distribution of damage in the Nahrin area. Houses built on the narrow crests of ridges eroded in loess suffered major damage due to the focusing of near-surface seismic waves on ridge-tops. Houses on low fluvial terraces along the Nahrin River also suffered major damage, likely due to their close proximity to the water table. Structures built on metamorphic bedrock and alluvial fans along the range front of the Hindu Kush Mountains or on high terraces along the Nahrin River suffered comparatively less damage. Building failure was predominantly caused by the mud-block construction, characteristic of much of Afghanistan and adjacent countries. Most houses are built of mud blocks made from reworked loess, which contains a relatively low percentage of clay. The walls contain no bracing against lateral shear, and wall corners are not tied together, leading to failure at corners and roof collapse. In several villages, mosques were constructed to a higher standard and suffered significantly less damage than surrounding mud structures. The mosques often had concrete foundations and structural supports tied to the foundations. Had houses been built to the same standards as most mosques, loss of life would have been greatly reduced.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2002
- Bibcode:
- 2002AGUFM.S71B1099M
- Keywords:
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- 7223 Seismic hazard assessment and prediction