Afghanistan + 2 more

USGS earthquake bulletin: Hindu Kush Region, Afghanistan (revised)

Format
Situation Report
Source
Posted
Originally published
Date-Time 2002 03 25 14:56:33 UTC
Location 35.93N 69.19E
Depth 8.0 kilometers
Magnitude 6.1
Region HINDU KUSH REGION, AFGHANISTAN
Reference 100 miles (155 km) N of KABUL, Afghanistan
Source USGS NEIC

The following is a release by the United States Geological Survey, National Earthquake Information Center: A moderate earthquake occurred about 100 miles (160 km) north of Kabul at 7:56 AM MST, Mar 25, 2002 (7:26 PM local time in Afghanistan). The magnitude and location may be revised when additional data and further analysis results are available.

Update: At least 1,800 people killed, 4,000 injured, 1,500 houses destroyed in the Nahrin area. Approximately 20,000 people homeless. Felt strongly in much of northern Afghanistan. Also felt in the Islamabad-Peshawar area, Pakistan and Dushanbe, Tajikistan.

Tectonic Setting

This shallow earthquake occurred near the boundary of the Eurasian and Indian tectonic plates. The two plates are converging at a rate of about 1.8 inches (4.5 centimeters) per year.

This convergence generates complex stresses in the region resulting from both subduction and rotation of continental blocks. Major tectonic features in the region include the Darvaz-Karakul fault, the Harat fault, the Chaman fault, and the Indus-Tsangpo suture zone.

The earthquake occurred within the Earth's crust, at a depth of 8 kilometers. Seismic waves recorded world-wide imply that the earthquake resulted from slip on a north-trending reverse fault. Several mapped faults in the region have orientations similar to the fault that caused the earthquake, although seismologists have not yet associated the earthquake with a specific mapped fault.

The Hindu Kush region is highly seismic. On average, there are about five magnitude 5 or greater earthquakes per year whose epicenters are within 100 miles (161 kilometers) of this event. Earthquake depths in this region range from the surface to depths of 205 miles (330 kilometers).

The earthquake is the result of geologic processes that have been active for millions of years; its occurrence is independent of the recent bombing in Afghanistan.

SHALLOW EARTHQUAKES CAUSE MORE DEATHS AND DAMAGE THAN INTERMEDIATE ONES

The earthquake of March 25 is another tragic example that shallow earthquakes cause more casualties and damage than intermediate depth ones (depths between 70 and 300 km -- about 45 and 185 miles) such as the event on March 3. Shallow earthquakes cause more damage than intermediate and deep ones since the energy generated by the shallow events is released closer to buildings and therefore produces stronger shaking than is generated by quakes that are deeper within the Earth. The more-destructive earthquake on March 25 actually produced about 95 times less energy than the event on March 3, but it has caused much more damage.

A similar combination of nearby shallow and intermediate earthquakes occurred in 1998. On February 4, 1998, a magnitude 5.9 shallow earthquake struck 150 km (95 miles) northeast of the March 25 quake. That earthquake killed at least 2,323 people, injured 818 and destroyed 8,094 houses in the Rostaq area of Afghanistan. A magnitude 6.6 earthquake, also shallow, hit the same area on May 30, 1998, and killed at least 4,000 people and destroyed many homes in Badakhshan and Takhar Provinces.

By comparison, on February 20, 1998, a magnitude 6.4 earthquake occurred about 180 km (110 miles) east-northeast of the March 25 event or about 60 km (35 miles) east of the March 3, 2002 earthquake, at a depth of about 235 km (145 miles) below the surface. That earthquake killed only one person and destroyed 35 houses in northern Pakistan.

Shallow-depth earthquakes:
1998 Feb 04 14:33:21 37.075N 70.089E 33 km 5.9M at least 2,323 killed
1998 May 30 06:22:28 37.106N 70.110E 33 km 6.6M at least 4,000 killed
2002 Mar 25 14:56:33 35.933N 69.194E 8 km 6.1M at least 1,500 killed; maybe as many as 5,000

Intermediate-depth earthquakes:
1998 Feb 20 12:18:06 36.479N 71.076E 236 km 6.4M 1 person killed
2002 Mar 03 12:08:12 36.471N 70.401E 252 km 6.2M foreshock of event below
2002 Mar 03 12:08:22 36.543N 70.424E 256 km 7.4M at least 113 killed, 100 of them from a landslide triggered by the quake