| ARE WE LIKELY TO BE IN THE PATH OF TSUNAMI? |
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| Pakistan has a coast line that is stretched to over 1000 km along the Arabian Sea it comprises two distinctive units, the passive margin of Sindh; and the active margin coast of Blochistan coast. The coastal shore geology of Pakistan tectonically exhibits both active and passive margin feature. |
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| The Balochistan coast stretches over a distance of about 670 km from the Hub River in the east to the Gawatar Bay in the west. The area is arid with only 150mm rain fall /year the coast is drain by small rivers Hingol, Basol, Shadi Khor and Dasht. Despite having large catchments areas, these river flows only during rainy session flash floods are frequented. |
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| Geomorphic features of Blochistan let Makran coast are clip, had land geomorphic and mud volcanoes. Rocks exposed along the coast are the assemblages of sand, shell, and mud stone. the mountain are compose of bare rocky lime stone or conglomerate, with the exception of some upper high land; there is little or no vegetation, spectacular mud volcanoes are found in several location along the Coast erupting gas-charged liquid-mud. |
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| Balochistan margin is an active subduction zone where the Arabian plates move at a rate of 50 mm/year north word under continental crust. The subduction zone is about 900 km long, stretching from near the straits of Hormuz in the west to Karachi in the east. The continental shelf is narrow and steep. Along the Makran margin the shelf with suddenly narrows to about 40 km and further decreases gradually towards the west. The Makran continental’s margin illustrates terraces like features. |
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| Northeast southwest oriented Murray Ridge in the Arabian Sea is complex structures stemming from Owen fracture complex and influence by the Makran subduction. It is characterizes by seismcity, varied sedimentation and morganatic activity. It is consist of seamounts, scraps and small basins in a linear pattern. it extends from the continental slop near Karachi over 750 km towards southwest .the Murray Ridge has a maximum relief of about 2000m in the middle part and a relief as large as 3500 m in its southern part. The dregs sample in the Murray Ridge zone shows volcanic rocks. |
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| The continental shelf of Pakistan is a wind –force shelf, influenced by summer monsoonal winds that are in excess of 30 knot that below in the south west directions. High energy waves in the SW monsoon influences the process of erosion. Coastal upwelling also prevails along Pakistan coast, which induced higher primary productivity. Pakistan’s coastal areas are among the most biologically productive areas (50-200g C/m³ per year). . Any major perturbation (climatic change/sea level rise) or change to the ecological balance of established communities would destabilize species diversity that would reduce its efficiency in the flow of energy. |
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| In the minutes preceding a tsunami strike, the sea often recedes temporarily from the coast. People in Pacific regions are more familiar with tsunamis and often recognize this phenomenon as a sign to head for higher ground; however in the Indian Ocean region, this rare sight reportedly induced people, especially children, to visit the coast to investigate and collect fish stranded in as much as 2.5 km of exposed beach land, with fatal results. |
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| Effect Noticed in Arabian Sea near the coast of Karachi. |
| Dec. 26th Divers from “Karachi Scuba Diving Club” were diving at Bachum Reef near cherna Island, the visibility was 40 ft. The reef was full of life. After finishing dive when divers reached to Mubarak Village they observed very low tide pretty unusual for this time of year, and observed a change pattern in the tidal cycle through out the week. |
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| For the next week the underwater visibility was variable from 10 ft. to 100ft. a strange phenomenon, the marine life seen in that period was peculiar for this part of world, the most strange thing diver noticed on 31 Dec. 2004 after completing a dive of 100 ft when we were hanging at 15 ft for decompression stop we saw one lonely snake around 10ft long curiously circling around us Rosheen was little apprehension but what I noticed the snake was brownish in color with black spots on its head, the kind of snakes we see in this water are brightly colored and have small rounded shape mouth. |
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| Flexibility and ductility of the buildings play a major role in earthquake resistance, when seismic waves spread through the earth’s various media, a number of waves of different frequencies begin to interact with each other. This distribution of frequencies in ground motion is called frequency content. The building that is now vibrating itself possesses its own natural frequency. The shorter the building the higher its natural frequency and the taller the building the lower its natural frequency. When the ground vibrates with the same frequency as the natural frequency of the building, resonance occurs. This amplifies the magnitude of the whole vibration waveform. When in resonance or close to it, an object absorbs more energy and vibrates more easily. This is the reason why during an earthquake one building may collapse as nothing happens to the adjacent buildings. |
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| With high-rise buildings gaining popularity in Karachi, Lahore and Islamabad, it is time that we got out of our slumber and did something about the structures of our buildings. It is surprising that the government has yet to order inspection of the existing buildings for safety. |
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| Many of our major cities are within striking distance of the seismic faults zones. If even now we don’t do anything worthwhile about building safety we will be courting disaster. |
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| In fact as far as Pakistan coastal environmental safety is concerned, it is in danger from the illicit waste disposal into our shipping lane by the industrial countries that produce 99% of the dangers waste of the world, which total up to 4,400 mt/year. It is not known how much has been dumped in Pakistan waters. Danger waste when dumped in to the sea reached the bottom and mixes with bottom sediment. During the southwest monsoon in the Arabian sea, cold water plumes and wedges extend eastward along with upwelling (Quraishee 1984) with circulation end up welling bottom sediment contaminated with dangers material may reach the Pakistan coast. These demand periodic checks for a number of heavy metals and hazardous material. |
