Rise of Himalayas giving rise to quake proneness

KATHMANDU: Scientists have said there is a gradual upliftment of the Himalayas due to the collision of Indian and Tibetan plateaus, making the region more susceptible to earthquake.

Nepal lies at the centre of the seismo-tectonically active Himalayan belt. The central 800-km of the 2400-km long Hindu Kush Himalaya lies in Nepal and the collision of the Indian plate with the Tibetan one is considered a major reason to justify the seismicity in the Himalayas.

Scientific studies reveal that Indian plate is under-thrusting towards the Tibetan plate in the north. The Indian plate continues to move northward relative to Asia about 5 cm per year, according to scientists. A report of National Aeronautics and Space Administration (NASA) on the Himalayan front and Tibetan plateau

states, “Given the great magnitudes of the blocks of the earth’s crust, this is a remarkable rate that the uplift of the Himalayas is about twice the speed at which fingernails grow.”

According to the NASA report, the continuing northward compressional movement of India has produced intracontinental thrust sheets responsible for the highest mountains in the world. Mount Everest, the Annapurna Range, and the rest of the Himalayas are still rising, and the region remains seismically active.

The report adds that the effects of this collision are widespread, being responsible for the 2500-km long thrust front of the Himalayas that extends from the Hindu Kush on the west to the Burma Ranges on the east and for the creation of tectonically bonded basins like Kashmir and Kathmandu developed on the back slopes of the frontal thrusts.

There has not been any systems developed by the scientists which could predict the earthquake. In 1931, there were about 350 seismographic stations operating in the world to record the quakes; today, there are more than 4,000 stations and the data now comes in rapidly from these stations by telex, computer and satellite.

In Nepal, there are 21 short period telemetric seismic stations and 22 Global Positioning System stations to record the earthquake.

Nepal’s geotectonics

Geologist have divided Nepal into five distinct morpho-geotectonic zones, from south to the north — Tarai Plain, Sub Himalaya (Siwalik Range), Lesser Himalaya (Mahabharat Range and mid valleys), Higher Himalaya and Inner Himalaya (Tibetan Tethys). Each of these zones is clearly identified by their morphological, geological and tectonic features. Main Frontal Thrust, Main Boundary Thrust, Main Central Thrust and South Tibetan Detachment Fault system, from south to north respectively, are major linear geological structures that act as the boundary-line between the two consecutive zones. The areas lying in these zones are more prone to earthquake.

Frequency of earthquakes worldwide

Magnitude Average annually

8 and higher 1

7-7.9 17

6-6.9 134

5-5.9 1,319

4-4.9 13,000 (Estimated)

3-3.9 130,000 (Estimated)

2-2.9 1,300,000 (Estimated)

Source: NASA

Timeline of earthquakes in nepal

1310 BS / 1255 AD

The first recorded earthquake in the history of Nepal was on June 7, 1255 AD. One-third of the total population of Kathmandu was killed, including Abahya Malla, the King of Kathmandu Valley, while numerous buildings and temples were completely destroyed. The magnitude of the earthquake was said to be around 7.7 on the Richter scale.

1316BS / 1260 AD

Another major recorded earthquake after 1255 AD was during the reign of King Jayadev Malla. Although the exact number of fatalities was not confirmed, we now know from the facts availabale that there was a heavy loss of life in the earthquake and from an epidemic and famine that followed.

1463BS/ 1408AD

The month of either August or September of this year saw another major earthquake hit the valley of Kathmandu and its surrounding areas during the reign of King Shyam Singh. The temple of Rato Matchendranath was completely destroyed, while many other temples and buildings collapsed and were damaged. There was a heavy loss of lives and livestock.

1737BS / 1681 AD

Either on the month of December or January, during the reign of King Sri Niwas Malla, another major earthquake hit Nepal and the Kathmandu Valley. Very little information is available on this earthquake.

1767 AD

In the months of June and July, another major earthquake seemed to have hit Nepal. It is said 21 aftershocks were felt in a span of 24 hours. No written or verbal records are available to indicate any human loss or the magnitude of sufferings and damages caused.

1866 BS/ 1810 AD

During the reign of King Girban Yudha Bikram Shah in the months of May or June 21 temblors were felt in Nepal. Although the loss of lives was limited, many houses, building and some temples were damaged.

1880 BS / 1823AD

Seventeen tremors of various magnitudes were felt in the Katmandu Valley, but these shocks probably were smaller as compared to the past earthquakes as there was no report of loss of human lives or livestock.

1890 BS/ 1833 AD

During the reign of King Rajendra Bikram Shah on the months of August or September, two major tremors were experienced in the Kathmandu valley. The first one was felt at around 6 pm, while the second one hit at around 11 pm when most of the valley people were asleep. Houses, temples, public shelters collapsed. The tower of Dharahara was also severely damaged. The towns of Thimi and Bhaktapur bore the brunt of the disaster. A total of 4,214 houses were destroyed then.

1891 BS/ 1834 AD

Four major earthquakes were felt in the months of June and July. These earthquakes destroyed or damaged many buildings and temples. However, the extent of the damage was much less than the previous ones. A lashing rain had hampered the search and rescue operations. The Bagmati River was flooded and a bridge over the river was swept away. Over 18,000 houses collapsed all over the country then.

1990 BS/ 1934 AD

Magh (January- February) Earthquake, Known as the ‘Great Nepal-Bihar Earthquake’ struck Nepal and it’s surrounding areas around 2 pm on January 16. The magnitude of the earthquake was 8.4 on the Richter scale. Casualty figures were the highest for any recorded earthquake in the history of Nepal. In total, 8519 people lost their lives, a total of 1,26,355 houses were severely damaged and around 80,893 buildings were completely destroyed. The total money spent from the earthquake relief fund was Rs 2,06,500 in the Kathmandu valley only. The relief fund was established by the king; loans were provided for earthquake effected people and earthquake volunteers’ groups were formed.

2045 BS/ 1988 AD

The Udayapur Earthquake mostly affected the Eastern Development Region, while some parts of the Central Development region were also affected. There were 721 deaths, while 6,553 people were injured. A total of 64,174 private buildings, 468 public houses and 790 government buildings were damaged. The total direct loss amounted to Rs 5 billion. The World Bank had approved a loan of Rs 1 billion then.

2050 BS/ 1993 AD

A quake affected the Central region and Mid-Western region, killing one person and leaving 11 others injured, 72 houses destroyed.

2051 BS/ 1994 AD

The Mid-Western Region was affected by an earthquake, injuring 12 people, while 623 houses were destroyed and 84,287 buildings were damaged. The total loss was put at Rs 16.35 million.

2052 BS/ 1995 AD

A quake hit the Mid-Western Region - Dailekh. Eighteen people were affected, while four houses were destroyed. The total loss amounted to Rs 1.02 million.

2054 BS /1997 AD

One person was injured, while 1489 people were affected. A total of196 houses were destroyed, 60 buildings damaged.

2058 BS/ 2001 AD

The Far-Western region and some parts of the Western and Central regions were affected by another quake, leaving two persons dead and destroying three houses.

2059 BS/ 2002 AD

A minor quake jolted Mohatarri in the Central region injuring 41 people.

2060BS/ 2003 AD

Another minor temblor hit Syangja of the Western Region killing one person and leaving two others injured.

(Sources: Disaster Preparedness Network Nepal, DesInventar NSET, Seismic Hazard Mapping and Risk Assessment for Nepal, UNDP/ UNCHS (Habitat) Subproject)