Earthquake in nepal 2011

 An earthquake measuring 5.7 on the Richter Scale rocked the far western region today damaging more than two dozen houses in Bajhang, Baitadi and Darchula. According to the National Seismological Centre, the epicentre of the quake was in Chhapri of Darchula district, near Nepal-India border.

The tremor hit the region at around 5:16 pm and lasted 15 seconds. No human casualties were reported though.

“The duration of the quake was 15 seconds and it was of medium-type in nature,” said Bharat Koirala, Seismologist. NSC has recorded five small-scale earthquakes in Nepal in the last one month but the today’s was the largest.
History of Earth Quake in Neapl 
Nepal, a landlocked country, has its own history of earthquake. Earthquake, one of the most dangerous natural disasters is being experienced by various people in various places. Not only Nepal, many of the countries are proclaimed as seismic prone countries. Men have been able to fight or deal many challenges but not with natural disasters till now. Men, in fact, are not able to defeat natural disasters but we can control it by adopting many ways.


Although we cannot find actual, reliable and formal documents about earthquake in Nepal. many data are being collected being based on informal historical documents, rock/stone inscription, copper inscription and other many documents.

As we know that the earthquake, which took place in Antique city of Syria on 20th May 516 A.D is the first earthquake in the world, Nepal experienced the first earthquake in 1198 A.D (1255 B.S) which is known as the oldest powerful earthquake. In some books this very first date is written as 1253 A.D(1310 B.S). As if it is called as the biggest earthquake as data is available. By that first earthquake, the then king Abhaya Malla was killed, many people were killed and physical infrastructure was destructed in large quantity. After the occurrence of that earthquake, it shook land for 15 days constantly.



Another huge earthquake took placce in 1259 A.D(1316 B.S) which we can find in many documents. Likewise in 1407 A.D(1464 B.S) another earthquake had taken place which destructed Machhindranath temple as well as many other temples, inns, and land was separated into many pieces. Many documents have quoted these incidents.

If we study the history of earthquake in Nepal, we find that earthquake has taken place more in 1624 A.D (1681 B.S), 1680 A.D (1737 B.S), 1681 A.D (1738 B.S), 1753 A.D (1810 B.S), 1767 A.D(1824 B.S), 1809 A.D (1866 B.S), 1823 A.D (1880 B.S), 1834 A.D (1891 B.S), 1916 A.D (1973 B.S), 1926 A.D (1983 B.S) respectively. Although these earthquakes were of disparaging muscle , they did destruction however in small quantity or huge quantity.

Earthquake, which took place in 1933 A.D (1990 Magh 2) and was of 8.3 rector scale is claimed to be the most powerful earthquake ever took place in Nepal, making Kathmandu, the capital city as the centre, has enough formal evidences. Being based on that earthquake the then major general of Army Staff Brahma shamsher had written one book named Maha Bhukampa- 1990 (Huge Earthquake-1933). Because of that earthquake 8519 people were coerce to die. Among that total death number 3850 were male and 4669 were women. Dharahara (nine stored building), Ghanta Ghar and other many temples, houses and other buildings were destructed.

Another earthquake took place in far western region in 1966A.D (2023 B.S), which killed 24 people and at least 1300 houses were completely destructed. Moreover, in 1980 A.D (2037 B.S), Bajhang district faced the effects of earthquake, which was also badly affected. In that earthquake 103 people were killed whereas 2500 houses were destructed.

However, again nine hundred people died because of earthquake in Udayapur district in 1988 A.D (2045 B.S) which also destructed many physical infrastructure.

In this way, Nepal, one of the seismic prone countries faced many earthquakes in different places. Many organizations, today are working to spread knowledge about the symptoms, causes, techniques to live from earthquake etc.

Folds

The term fold is used in geology when one or a stack of originally flat and planar surfaces, such as sedimentary strata, are bent or curved as a result of permanent deformation. Synsedimentary folds are those due to slumping of sedimentary material before it is lithified. Folds in rocks vary in size from microscopic crinkles to mountain-sized folds. They occur singly as isolated folds and in extensive fold trains of different sizes, on a variety of scales. Folds form under varied conditions of stress, hydrostatic pressure, pore pressure, and temperature - hydrothermal gradient, as evidenced by their presence in soft sediments, the full spectrum of metamorphic rocks, and even as primary flow structures in some igneous rocks. A set of folds distributed on a regional scale constitutes a fold belt, a common feature of orogenic zones. Folds are commonly formed by shortening of existing layers, but may also be formed as a result of displacement on a non-planar fault (fault bend fold), at the tip of a propagating fault (fault propagation fold), by differential compaction or due to the effects of a high-level igneous intrusion e.g. above a laccolith.

Fold terminology in two dimensions

Looking at a fold surface in profile the fold can be divided into hinge and limbcurvature for a fold. The crest of the fold is the highest point of the fold surface, and the trough is the lowest point. The inflection point of a fold is the point on a limb at which the concavity reverses, on regular folds this is the mid-point of the limb. portions. The limbs are the flanks of the fold and the hinge is where the flanks join together. The hinge point is the point of minimum radius of

Fold terminology in three dimensions

The hinge points along an entire folded surface form a hinge line, which can be either a crest line or a trough line. The trend and plunge of a linear hinge line gives you information about the orientation of the fold. To more completely describe the orientation of a fold, one must describe the axial surface. The axial surface is the surface defined by connecting all the hinge lines of stacked folding surfaces. If the axial surface is a planar surface then it is called the axial plane and can be described by the strike and dip of the plane. An axial trace is the line of intersection of the axial surface with any other surface (ground, side of mountain, geological cross-section).
Finally, folds can have, but don’t necessarily have a fold axis. A fold axis, “is the closest approximation to a straight line that when moved parallel to itself, generates the form of the fold.” (Davis and Reynolds, 1996 after Donath and Parker, 1964; Ramsay 1967). A fold that can be generated by a fold axis is called a cylindrical fold. This term has been broadened to include near-cylindrical folds. Often, the fold axis is the same as the hinge line.

Homogeneous and Heterogeneous Strain

Mathematical treatments of strain commonly assume homogeneous rather than heterogeneous distortions or strains. However, any heterogeneously strained rock body can be subdivided into small areas that exhibit the characteristics of homogeneous strain. Heterogeneous strain affects non-rigid bodies in an irregular, non-uniform manner and is sometimes referred to as non-homogeneous strain (Figure 28). During heterogeneous strain parallel lines before strain are not parallel after strain, while circles and squares or their three-dimensional counter parts cubes and spheres are distorted into complex forms. Homogeneous strain affects non-rigid rock bodies in a regular, uniform manner (Figure 29). During homogeneous strain parallel lines before strain remain parallel after strain, as a result cubes or squares are distorted into prisms and parallelograms respectively, while spheres and circles are transformed into ellipsoids and ellipses respectively. For these generalizations to hold true, the strain must be systematic and uniform across the body that has been deformed.

Figure 28. Heterogeneous or non-homogenous strain results in distorted complex forms.

Figure 29. Homogenous strain affects bodies in a regular and uniform manner.

Earth Structure

Advances in seismology, computer modeling, and mineralogy and crystallography at high temperatures and pressures give insights into the internal composition and structure of the Earth.
Seismologists can use the arrival times of seismic waves in reverse to image the interior of the Earth. Early advances in this field showed the existence of a liquid outer core (where shear waves were not able to propagate) and a dense solid inner core. These advances led to the development of a layered model of the Earth, with a crust and lithosphere on top, the mantle below (separated within itself by seismic discontinuities at 410 and 660 kilometers), and the outer core and inner core below that. More recently, seismologists have been able to create detailed images of wave speeds inside the earth in the same way a doctor images a body in a CT scan. These images have led to a much more detailed view of the interior of the Earth, and have replaced the simplified layered model with a much more dynamic model.

Mineralogists have been able to use the pressure and temperature data from the seismic and modelling studies alongside knowledge of the elemental composition of the Earth at depth to reproduce these conditions in experimental settings and measure changes in crystal structure. These studies explain the chemical changes associated with the major seismic discontinuities in the mantle, and show the crystallographic structures expected in the inner core of the Earth.

About Rock in Geology

There are three major types of rock:
1.igneous,
2.sedimentary, and
3.metamorphic.
The rock cycle is an important concept in geology which illustrates the relationships between these three types of rock, and magma. When a rock crystallizes from melt (magma and/or lava), it is an igneous rock. This rock can be weathered and eroded, and then redeposited and lithified into a sedimentary rock, or be turned into a metamorphic rock due to heat and pressure that change the mineral content of the rock and give it a characteristic fabric. The sedimentary rock can then be subsequently turned into a metamorphic rock due to heat and pressure, and the metamorphic rock can be weathered, eroded, deposited, and lithified, becoming a sedimentary rock. Sedimentary rock may also be re-eroded and redeposited, and metamorphic rock may also undergo additional metamorphism. All three types of rocks may be re-melted; when this happens, a new magma is formed, from which an igneous rock may once again crystallize.
The majority of research in geology is associated with the study of rock, as rock provides the primary record of the majority of the geologic history of the Earth.

Scope of Geology in Nepal.

What does geology means? It means the study of the earth. It also means the study of the all aspects related to earth like it undertakes the study of matter that constitutes the earth. It has a broad scope because it also covers the study of structure, composition, physical properties, and history of Earth. It also discusses various processes of earth like how it was formed, how it moves and how it has changed over a period of time. Geology is also linked with industrial study and engineering because industrial studies deals with the mineral extractions which are found on earth and engineering is closely linked with geotechnical aspects of earth.

The scope of geology is vast and it include the study of atmospheric Science includes the physics, chemistry, and dynamics of the atmosphere; and many of the interactions between the atmosphere, solid earth, and oceans.
Geology also includes scope of geology is broad, specialized branches have evolved. For example, geomorphologists investigate the nature and origin of land forms by studying the causes and effects of dynamic earth processes; structural geologists are concerned with the arrangement of rock masses in the earth’s crust and the types of forces that have affected them; and stratigraphers investigate the thickness, geometry, and distribution of layered rocks to understand the chronology of geologic events.
So student will have a great future and they can make a better career in these fields and from advice student will have a great fun to work and to study about the physical beauties of the earth.

Read more here: http://www.geology.edu.np