Structural and Tectonic Control of Karachi (Pakistan) and the Possibilities of Seismic Hazards

Abstract

Urban planning becomes an important issue where urban areas expand as a result of an increase in urban population. The objective of
urban planning is to reduce the number of conflicts and environmental impacts so that the quality of life and the general welfare of the
community are improved. In urban planning geological data are becoming increasingly important for the recognition, control and prevention of
natural hazards and disasters. Historically earthquakes are one of the major natural hazards that have caused devastation in terms of high
number of human lives, wide spread building and infrastructure failures and sufferings, as remains of an earthquake.
The major transcurrent and transverse faults and also the minor active or dormant faults in different parts of the Karachi city are self
explanatory and need careful consideration the selection of sites for civil structures of industries or sky scrapers for human livings. The known
active faults are expected toprovide fairly good information for the assessment of possibility of seismic hazards in Karachi area especially with
reference to the work of Kukowski et al (2000) who discovered sinistral strike slip fault and named it as Sonne Fault. This obliquely crosses the
wedge and continues to abyssal plain of north Arabian Sea and separate the western part of Makran subduction zone from the eastern part. The
Ormara plate is considered as a tearing of the Arabian plate along the Sonne Fault. Shahid et al (2003) concluded from their study of
seismotectonic and geology of the coastal area of Pakistan that the faults are potential sources of hazards. Karachi lies 150 km east of the triple
junction between the Arabian, Indian and Eurasian plates formed by the intersection of Owen fracture zone, the Makran subduction zone and
the Ornach-Nal fault. In the light of the historical data and the work done in the recent past, the present location of Karachi and its surrounding
areas appear in the zone of severe damage where the intensity of expected shock waves are to be between 6 to9 on Richter scale.