Earthquakes
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Describe the different Seismic discontinuities
Seismic discontinuities are boundaries within the Earth where seismic wave velocities change abruptly. These changes indicate differences in composition, phase, or state within the Earth's interior. Mohorovičić Discontinuity (Moho): Located at an average depth of 35 km beneath continents and 7 km beRead more
Seismic discontinuities are boundaries within the Earth where seismic wave velocities change abruptly. These changes indicate differences in composition, phase, or state within the Earth’s interior.
These discontinuities help scientists understand the internal structure and composition of the Earth, providing crucial insights into geological processes and the dynamics of Earth’s interior.
See lessDefine seismic retrofitting and explain its importance in making buildings and infrastructure earthquake-resistant. Provide some examples of successful retrofitting projects in India.
Seismic retrofitting refers to the process of modifying and strengthening existing buildings, infrastructure, or structures to improve their ability to withstand seismic (earthquake) activity. This involves making structural and non-structural changes to reduce the risk of damage or collapse duringRead more
Seismic retrofitting refers to the process of modifying and strengthening existing buildings, infrastructure, or structures to improve their ability to withstand seismic (earthquake) activity. This involves making structural and non-structural changes to reduce the risk of damage or collapse during an earthquake, thereby enhancing the safety and resilience of the structure and its occupants. Strengthening an old brick building with steel braces and reinforced concrete serves as an example.
Importance of Seismic Retrofitting in Making Buildings and Infrastructure Earthquake-Resistant:
Some Examples of Successful Retrofitting Projects in India:
Seismic retrofitting stands as a crucial process in fortifying the earthquake resilience of buildings and infrastructure. By prioritizing seismic retrofitting today, we can not only safeguard lives and assets but also lay the foundation for a safer and more resilient future for generations to come.
See lessHighlighting the different types of earthquake waves, discuss the emergence of shadow zones.
Answer: Earthquake waves, also called seismic waves, are basically of two types- body waves and surface waves. Body waves are generated due to the release of energy at the focus and move in all directions traveling through the body of the earth. Body waves are of two types: P-waves: They are the firRead more
Answer: Earthquake waves, also called seismic waves, are basically of two types- body waves and surface waves. Body waves are generated due to the release of energy at the focus and move in all directions traveling through the body of the earth. Body waves are of two types:
When body waves interact with the surface rocks, they generate a new set of waves called surface waves. These waves move along the surface. They cause displacement of rocks, and hence, the collapse of structures occurs. Surface waves are of two types:
Shadow zone: Though earthquake waves get recorded in seismographs located at far-off locations, there exist some specific areas where the waves are not reported. Such zones are called ‘shadow zones’. It was observed that seismographs located at any distance within 105° from the epicenter, recorded the arrival of both P and S-waves. However, the seismographs located beyond 145° from the epicenter, record the arrival of P-waves, but not that of S-waves. Thus, a zone between 105° and 145° from the epicenter was identified as the shadow zone for both types of waves. The entire zone beyond 105° does not receive S-waves. The shadow zone of the S-wave is much larger than that of the P-waves and is a little over 40 percent of the earth’s surface.
Seismologists have concluded that the emergence of the shadow zone is because of the internal structure of the earth which is not homogeneous. Earth’s interiors have an uneven density which leads to the emergence of shadow zones. The shadow zone of P waves has led to the identification of boundaries between the mantle and core. Further, it has also been deduced that the outer core is made of liquid, as S-waves cannot travel through liquid mediums and P-waves are refracted by the liquid core. Thus, the concept of the shadow zone has helped seismologists get information about the interior of the earth’s surface.
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