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A series of tremors have been felt in the Karachi metropolitan area since mid-July 2005. Seismic activity is continuing into November 2005. This sequence has been punctuated by several marked events that were widely felt. The magnitudes or epicentres of these events are not known. These tremors have given rise to baseless rumours and many people fear a larger earthquake in the future.

Earthquake swarms can be defined as clusters of earthquakes, which may number in hundreds or even thousands. They have no well defined mainshock and most the the larger events are of the same magnitude. They occur within a limited area and their duration may vary from a few hours to several months. Swarms are a result of different reasons such as the formation of new faults, fault creep, increase of pressure of fluids at depth and in regions susceptible to volcanic activity i.e. by the movement of magma beneath the surface. Historically, a short-lived swarm was reported from near the city of Faisalabad in Punjab in September 1943. Some buildings suffered minor damage in villages along the borders of Faisalabad & Shekhpura districts. In the state of Gujarat in India, adjoining Sindh province in Pakistan, seismic swarms have occurred in the past. The most widely publicized swarm in India struck Bhavnagar in Gujarat in August 2000 and lead to widespread panic in the city. Swarms have also been recognized at Rohtak in Haryana, Sikar in Rajasthan, Khandwa and Seoni in Madhya Pradesh, at Jawahar, Koyna, Latur, Nashik and Thane in Maharashtra and at Jamnagar and Rajkot in Gujarat.

NOTABLE EVENTS
Listed below is felt information sent in to the ASC via the Felt a Quake? page. This information is supplemented with additional media reports where ever available. Please bear in mind that this information in preliminary in nature and will change or be removed without prior notice.

16 July 2005 - 04:48 PST
Two minor tremors were recorded by the PMD, one at 04:48 PST and this was followed by another event at 10:47 PST.  The first was felt indoors in the Defence Society-Dow Medical College area of Karachi. Many people were woken up and ran outdoors. Mild rocking of cars was also seen.

6 August 2005 - ~22:15 PST
Felt indoors in the Defence Society-Dow Medical College area of Karachi. It was accompanied by a rumbling sounds, caused loose objects to rattle and disturbed standing water.

13 August 2005 - 01:47 PST
Two minor tremors were recorded by the PMD at 01:47 PST and were followed by another event at 11:15 PST. Felt in the Defence Society-Dow Medical College area for 10-seconds. People were woken up and many ran outdoors in panic. A loud rumbling noise was heard and hanging objects shook. In one instance a parked car was seen shaking.  It was also felt in the vicinity of Karachi General Post Office (GPO) where sleeping persons were woken and slight rattling noises were heard. A person awake at the time did not feel the tremor.

12 October 2005 - ~00:30 PST
Felt indoors in the Cantonment area by a person awake at the time. It was accompanied by a loud rumbling noise and disturbed standing water. In Clifton, it was felt by some persons indoors for 2-3 seconds. It was also felt in the Bilawal House, Defence Beach, Defence Colony Housing, Gulistan-e Jouhar and Seaview areas of the city.

23 October 2005 - Between 17:30 & 18:02 PST
Felt indoors in the Defence Society-Dow Medical College area for about 4-seconds and was accompanied by a rumbling noise. It was felt by some people who were outdoors in the Defence area. Some people who were asleep at the time were woke up. Buildings developed hairline cracks in the Clifton area. It was also felt in most other places in coastal Karachi.

26 October 2005 - ~08:43 PST
Tremors were felt indoors in the Nursery Road area. This tremor lasted 10-seconds, causing hainging objects to shake and awoke a person who was asleep at the time. Hairline cracks also developed in walls.

References
01) Auden, J.B., "Note on the earthquake tremors at Shahkot, Sheikhpura district, Punjab of September 1943", Records of the Geological Survey of India, Vol. 78, pp.135-141.
02) Southern California Earthquake Center (SCEC)
03) Wessel, P., and Smith, W.H.F., "Free software helps map and display data", EOS Trans., AGU, 1991, 72, 441, 445.

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