The epicenter was near the city[b] of Bou'in-Zahra[c] in Qazvin province, a region of northwestern Iran which is crossed by several major faults that is known for destructive earthquakes.

[6] Iran is crossed by several major faults, with 90% of them being seismically active and subject to many earthquakes each year; the area around the rupture experiences minor quakes almost daily.

[14] The Bou'in-Zahra earthquake was located in an area of active thrust faulting and folding, parallel and south of the southern edge of the Alborz mountain range,[8] and was the 11th rupture in the previous two months in central Iran.

[7] A seismic inversion of long-period P and SH body-wave seismograms indicated a rupture on a thrust fault that dips 49 degrees to the southwest and had a centroid depth of roughly 10 kilometres (6 mi).

[8] A previously unmapped thrust with little surface expression, the Abdareh fault, has been identified from the disruption of earlier drainage systems by the growth of the fold in its hanging wall, and is thought to be responsible for the earthquake.

[15] Its duration was seven seconds,[2] and the epicenter was near the settlement of Bou'in-Zahra[9] in the Khar river valley,[8] a mountainous farming region[10] about 60 kilometres (37 mi) from the provincial capital of Qazvin.

[25] Damage to the historic Kharaqan tomb towers, which were in a good state of preservation before the event, suggests that the earthquake was possibly one of the most powerful in the region for approximately 900 years.

[8] At a station 28 kilometres (17 mi) from the epicenter, the maximum horizontal and vertical accelerations were recorded to be roughly 0.5 g and 0.26 g.[25] A bridge collapsed as a result of the disaster.

[19] Surface cracks were observed in Ab Darreh and Changureh, the villages that suffered the heaviest damage,[4] being roughly 25 kilometres (16 mi) from the epicenter.

[9] North of Avaj, in the village of Esmailabad, survivors recovered 38 corpses, a ninth of the total population, while searching for the missing, feared trapped in the ruins.

[6] The Red Crescent Society sent relief workers, detection dogs, 100 tons of food,[19] 1,000 tents, 2,500 blankets, and mobile kitchens to the earthquake-stricken area.

[9] United States President George W. Bush offered aid to Iran, which he had previously called part of an "axis of evil".

According to him, "human suffering knows no political boundaries" and he stood "ready to assist the people of Iran as needed and as desired".

[14] According to Hossein Rahnema, head of the Red Crescent in Changureh, the society "levelled an area to put up tents but most people wanted to stay next to their houses to look after their property".

They were warm during the day, although the villages grew colder at night, making rescue work harder and threatening the health of the homeless and anyone alive and trapped under the debris.

[33] On 23 June, "dozens" of Avaj residents threw stones at Interior Minister Abdolvahed Mousavi-Lari's car in anger at the government's delay in providing relief.

[34] Reconstruction of housing and infrastructure by provincial authorities was interrupted for almost four months (November 2002 – February 2003) due to harsh weather conditions.