Earthquake

Perhaps the Earthquake is the most fearful natural phenomenon in the human life. It is more so, because it is unpredictable and arrives without notice or without announcing it's vigor and strength. Scientists are constantly in search of this unknown. The major events of the earthquakes from the human viewpoint are realized on review of some major catastrophes. Minute observations and records at least have been able to pin point the focus or the epicenter of these earthquakes in the historical past. These studies could reveal two great seismic belts in the entire globe.

This article in fact, is just a browsing in the memory in response to the curiosity of Internet hunters. Therefore, it should start with the very basic question-

What Is An Earthquake?

Apparently the answer is simple - numerous tremors, both powerful and weak are the results of disturbances within the body of the earth itself logically are called Earthquake.

Why & How Earthquakes Happen? Reasons could be many; pinpointing is always after the event. They may be caused by various activities at the earth's surface such as ebb and the flow of the tides, the rush of traffic in the city streets, the tumbling of streams over high falls, magma tic outbursts from within the interior of the earth or explosion of high power nuclear or atomic bomb and so and so forth.


We should have first hand information about the two great seismic belts in the globe.  

What Are They? Most of the catastrophic events of earthquakes are associated with any of these two belts. Seismically active region in these two belts are categorized as follows

1. Western Coasts of North and South America, the Aleutian Islands and the island groups along the eastern Coast of Asia such as Japan and the Philippines and thus borders the Pacific Ocean on the east, north and the west.

2. It includes the Mediterranean, the Alps, the Caucasus and the Himalayas and continues into the East Indies, where it intersects the first belt. Uttaranchal- Assam and Andaman- Nicobar island chains fall within the second belt and thus face frequent earthquakes of devastating nature. 

Why It Happened?

It is known that the west Coast of India, as a whole, had been affected by numerous fault sets in the recent geological past around 80,000 to 1 million years before. Kathiawar coast with milliolite limestone was raised high from beneath the seabed. These faults are sharp N-S or E-W trending. The overall E-W trending Palghat Gap is well known. It lies across the Western Ghats in Kerala forming a major break in the continuity of the hills and connects Western Coastal Plain with the rest of the southern States. This landform or the Pass is bounded by steeply rising Nilgiri hills to the North and Anai Malai- Palni hills to the south. In the offshore about 90 km west of Ponnani there lies a topographic high known as Ponnani mount. It emerges at the continental slope adjoining shelf edge. ENE-WSW striking broad valley with steep northern wall has been observed about 25 km SE of the Ponnani Mount in the offshore. This valley, about 8 km wide fall in the same line with the Palghat Gap present in the NE of the area.

The other studies like magnetic observations confirm that the Palghat Gap is a faulted graben and continues beyond the land and towards the seabed in the offshore. Similar fault planes criss-cross this domain of Western Coast. Although these fault planes are inactive at present, it can reactivate to any extraneous force of considerable magnitude like impounding of sea waves or tides or even high power explosion & rush of heavy traffics. Incidentally, the area around Palghat Gap forms a weak zone with fault traces and contacts of younger rock formations like Vakrala sandstone with the oldest gneissic rock of more than 3000 m.years.
Who knows the famous festival of Trissur Pooram accompanying huge explosion of fire works and thousands of processions might aggravate the weak planes and causes tremors of human concern.