1993 Latur earthquake

1993 Latur earthquake      From Wikipedia, the free encyclopedia

The Latur earthquake struck India at 03:56 local time (UTC + 05:30) on September 30, 1993. The main area affected was Maharashtra State in Western India. The earthquake primarily affected the districts of Latur and Osmanabad including Ausa block of Latur and Umerga of Osmanabd. 52 villages were demolished in the intraplate earthquake. It measured 6.2 on the moment magnitude scale, and approximately 10,000 people died, whilst another 30,000 were injured. The earthquake's focus was around 12 km deep – relatively shallow – causing shock waves to cause more damage. Because India does not lie on a plate boundary there was some debate as to what caused the earthquake. One suggestion is the existence of fault webs. The Indian sub-continent crumples as it pushes against Asia and pressure is released. It is possible that this pressure is released along fault lines. Another argument is that reservoir construction along the Terna was responsible for increasing pressure on fault lines.
Killari, where the epicenter of the quake is believed to be, had a large crater, which remains in place to date.

Relief efforts

Several foreign and local donors reacted immediately to the tragedy by sending relief teams and rescue workers. The first convoy of over 120 trucks laden with relief material such as tents, blankets, food and clothing, medical supplies and temporary shelters given by international donors departed from Mumbai at around 10am on October 2, 1993. The Indian Army, State Reserve Police Force, Central Reserve Police Force and other law enforcement agencies rushed their personnel almost immediately after the quake, assuming there would be a greater number of casualties.

Among the first to respond were amateur radio operators from Mumbai and Hyderabad, who had rushed to Omerga, a town near Latur from where all quake-hit areas could be accessed by road. The Mumbai-based JNA Wireless Association undertook a special mission. With four-wheel drive vehicles given for the purpose by Mahindra and Mahindra, a group of eight Mumbai-based radio hams escorted the supplies convoy from Mumbai to Omerga. Later, the radio operators split into four groups and visited scores of ravaged villages, relaying vital information – such as possible outbreak of disease, food supply and devastation – to a control station set up in Omerga. During the 10 and a half day trip, these radio hams successfully assisted disaster mitigation efforts undertaken by the Indian government and private aid agencies.

Aerial view of Rhine Falls in Switzerland

Waterfalls are commonly formed when a river is young.^[1] At these times the channel is often narrow and deep. When the river courses over resistant bedrock, erosion happens slowly, while downstream the erosion occurs more rapidly.^[1][2] As the watercourse increases its velocity at the edge of the waterfall, it plucks material from the riverbed. Whirlpools created in the turbulence as well as sand and stones carried by the watercourse increase the erosion capacity.^[1] This causes the waterfall to carve deeper into the bed and to recede upstream. Often over time, the waterfall will recede back to form a canyon or gorge downstream as it recedes upstream, and it will carve deeper into the ridge above it.^[3] The rate of retreat for a waterfall can be as high as one and half meters per year.^[1]
Often, the rock stratum just below the more resistant shelf will be of a softer type, meaning that undercutting due to splashback will occur here to form a shallow cave-like formation known as a rock shelter under and behind the waterfall. Eventually, the outcropping, more resistant cap rock will collapse under pressure to add blocks of rock to the base of the waterfall. These blocks of rock are then broken down into smaller boulders by attrition as they collide with each other, and they also erode the base of the waterfall by abrasion, creating a deep plunge pool or gorge.
Streams become wider and shallower just above waterfalls due to flowing over the rock shelf, and there is usually a deep area just below the waterfall because of the kinetic energy of the water hitting the bottom. Waterfalls normally form in a rocky area due to erosion. After a long period of being fully formed, the water falling off the ledge will retreat, causing a horizontal pit parallel to the waterfall wall. Eventually, as the pit grows deeper, the waterfall collapses to be replaced by a steeply sloping stretch of river bed.^[1] In addition to gradual processes such as erosion, earth movement caused by earthquakes or landslides or volcanoes can cause a differential in land heights which interfere with the natural course of a water flow, and result in waterfalls.