The Earthquake of May 30, 1935 in Quetta, Balochistan
George Pararas Carayannis

Introduction

The largest earthquake to strike the Balochistan region in the 20th Century occurred on 31 May 1935, near Quetta - a very active seismic region of present-day Pakistan. The Quetta earthquake, as it was named, completely devastated the city of Quetta, killed between 35,000 to 60,000 people and injured thousands more in the region.

Date and Time of Origin: 19:00:46.9, on May 30, 1935 (UTC time and date); 02:33 A.M. local time (PST) on the 31 May 1935 (local date).

Epicenter: 27.39N, 88.75E, about 4.0 km SW of Ali Jaan in the Balochistan region of present day Pakistan.

Magnitude: There have been several reported magnitude value . A Moment Magnitude (Mw) = 8.1 asssigned to this event may have been an overestimate. Based on geometric seismic moment, the moment magnitude (Mw) of this earthquake was revised to range from Mw 7.7 - Mw 7.8.

Seismic Moment: 0.35*10*21 Nm, 0.63*10*21 Nm, 1.75*10*21 Nm.

Focal Depth: 17 kms.

Afteshocks: No foreshocks preceeded the main shock. The largest aftershock with magnitude Mw 5.8 occurred on June 2, 1935. It caused additional damage to Mastung, Maguchar and Kalat, but none at Quetta. Many smaller magnitude aftershocks followed in the region up to to October 1935.

Felt Reports and Ground Motions: The main shock was most intense in a small region surrounding the epicenter but its intensity diminishing rapidly with distance. According to reports, the shaking lasted for about three minutes. Widespread liquefaction was observed in the valley to the northwest of Quetta. Mud volcanoes erupted in this area, as well as near the village of Thok, near Surab. The eruption of the mud volcano at the latter location lasted for about nine hours.

The earthquake's ground motions were felt throughout present-day Pakistan, from Jatti in the south near Karachi, to Dera Ismail Khan in the north, to Chagai in the east, to Amritsar and Shimla, and as far away as Agra and Sultanpur in India and Afghanistan.

Surface Rupture and Crustal Dislocations

According to surveys carried out after the earthquake, there was no evidence of uplift along the thrust faults to the southwest of Quetta. However, to the west of the town, uplift of 20 centimetres was observed. The ground deformations ranged from 2-20 centimeters, mostly observed as cracks in alluvium deposits. The cracks extended for about 105 kilometers from the south side of the Chiltan range to Kalat. Ground dislocations on the western side of these cracks near Mastung, indicated uplift of as much as 80 centimentres on the average, while in some places the ground had raised up by as much as several meters. Near the Mastung Road train station the observed cracks ran across the Quetta-Nushki railway lines and had caused vertical deformation and offset or the tracks. The ground deformations indicated that the Quetta earthquake was associated with the zone of faults that runs along the eastern edge of the Chiltan range and extends south toward Mastung and Kalat. Based on these surveys it was concluded that the Quetta earthquake occurred on a strike-slip fault within the Ghazaband Fault Zone, along a segment that may have been stressed by the previous 1931 Sharigh and Mach earthquakes in the same region.

Death Toll and Damages

According to the same reports and surveys, all villages between Quetta and Kalat were destroyed by this earthquake and about 70% of the population had died or were injured. The majority of the fatalites (about 26,000) occurred in and around the town of Quetta. There was extensive destruction and collapse of government buildings and most of the people in the city's administration were killed. There was extensive damage to hospitals and hangar facilities at the airfield of the Royal Air Force Lines, where aircraft were damaged and became inoperative. A few of the reinforced concrete structures and a new railway stations fared better and suffered minor damage.

The infrastructure of the region was severely damaged. Communications from Kalat and Quetta to Chaman and Jacobabad were disrupted due to damage of telegraph lines. There was partial disruption of electrical service in Quetta, but the water supply continued uninterrupted. Rescue operations and clean up and salvaging by the military helped prevent major looting following the disaster. Prompt mass buials and cremations of the dead helped prevent the outbreak of an epidemic. Transportation routes were not badly damaged, though five segments of the Quetta-Nushki railway track had to be replaced as they were crisscrossed by fissures.

Mastung, another city south of Quetta, was severely damaged along with the Khan's palace. About 1,736 people reportedly were killed in this town. Similarly, the village of Sariab was flattened and 1,206 of its inhabitants lost their lives. There was extensive destruction at the village of Kansi where 1,010 people were killed. Another 710 people were reportedly killed at Tiri and 369 more at Pringabad. At the town of Kalat the destruction was severe and 120 people were killed. Overall, in the state of Kalat and in the Kalat tribal area, a total of 8,410 deaths occurred were reported with 5,000 more as injured. Nearly 100 villages in this region were devastated. Though the total number of fatalities from this earthquake are rough estimates, it is estimated that at least 35,000 peopleand perhaps as many as 60,000 may have been killed, which would make this earthquake the deadliest, up to that time, in present-day Pakistan' history.
Also the damage, was widespread outside the immediate region. Poorly-constructed buildings as far away as the Indus Valley and Kandahar and Spin Boldak in south-eastern Afghanistan were repertedly damaged.

Unusual and other phenomena (lights, mud volcanoes, landslides, rockfalls and dust clouds).

Several unusual phenomena were observed prior to the earthquake, mainly unusual lights. A bright light was observed west of Quetta. Near Kalat, flashes of light were reported as having occurred along the flanks of the mountains. Also, several landslides were triggered by the earthquake, particularly in the Shirinabad valley. Rockfalls occurred in the Chiltan range. Dust clouds from these landslides and rockfalls were seen rising 500 metres above the mountains.

Seismotectonic Setting - Seismicity of the Region

Northern, Western as well as Southern Pakistan, Kashmir and Northern India and Afghanistan are along zones of high seismic activity. Earthquakes occur along a very active thrust fault system in the region. Earthquakes along active faults in Pakistan and adjacent faults in India and Afghanistan are the direct result of the Indian subcontinent moving northward and colliding with the Eurasian continent at a rate of about 40 mm/yr (1.6 inches/yr). This major tectonic collision is causing uplift that produces the highest mountain peaks in the world including the Himalayan, the Karakoram, the Pamir and the Hindu Kush ranges.

Seismicity of Pakistan 1990 - 2000 (modified USGS graphic)

As the Indian plate moves northward, it is being subducted or pushed beneath the Eurasian plate. Much of the compressional motion between these two colliding plates has been and continues to be accommodated by slip on a suite of major thrust faults that are at the Earth's surface in the foothills of the mountains and dip northward beneath the ranges. These include the Main Frontal thrust, the Main Central thrust, the Main boundary thrust, and the Main Mantle thrust. These thrust faults have a sinuous trace as they arc across the foothills in northern India and into northern Pakistan.

Most of the earthquakes in Western Pakistan occur along the boundary of the Indian tectonic plate with the Iranian and Afghan micro-plates, mainly along the Chaman Fault System. The Chaman Thrust Fault system is a continuation on land of an extensive transform fault system in the Arabian Sea known as the Owen Fault Zone. The Chaman Fault System in Balochistan is a major fracture zone which begins near Kalat in the northern Makran range, passes near Quetta and extends along Pakistan's frontier with Afghanistan in a north-northeastern direction to Kabul - after branching off to form the Main Karakoram Thrust (MKT) System. Quetta and other towns and villages in western Pakistan are in close proximity to the most active seismic regions - the Chamman and the Chiltan fault lines.

References and Additional Reading

Ambraseys, N. and Bilham, R., 2003. "Earthquakes and Associated Deformation in North Baluchistan 1892-2001", Bulletin of the Seismological Society of America, Vol. 93 , No. 4, p. 1573 - 1605, 2003.

Lawrence, R.D., Khan, S.H., and Tanaka, T., 1992. "Chaman Fault, Pakistan-Afghanistan", Major Active faults of the World, Results of IGCP project 206, R. Buckham and P. Hancock (Editors), Annales Tect., 6 (Suppl.), p 196 - 223, 1992.

Ramanathan, K., and Mukherji, S., 1938. "A seismological study of the Baluchistan, Quetta, earthquake of May 31, 1935", Records of the Geological Survey of India, Vol. 73, p. 483 - 513, 1938.

Pacheco, Javier F., and Sykes, Lynn R., 1992. "Seismic moment catalog of large shallow earthquakes, 1900 to 1989 "Bulletin of the Seismological Society of America, Vol . 82, No. 3, p. 1306 - 1349 , 1992.

Pararas-Carayannis, G., 2005, The Earthquake of 8 October 2005 in Northern Pakistan

Pararas-Carayannis, G.,2006, The Great Makran Earthquake in the North Arabian Sea of 28 November 1945

Pararas-Carayannis, G., 2006, POTENTIAL OF TSUNAMI GENERATION ALONG THE MAKRAN SUBDUCTION ZONE IN THE NORTHERN ARABIAN SEA. CASE STUDY: THE EARTHQUAKE AND TSUNAMI OF NOVEMBER 28, 1945, http://drgeorgepc.com/TsunamiPotentialMakranSZ.html

Pinhey, L.A., 1938. "The Quetta Earthquake of 31 May 1935", Government of India, New Delhi, 1938.

Thompson, R.O.C., 1936. "Notes on the Quetta Earthquake", Technical Paper 307, Railway Board, Lucknow, 1936.

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