CHAPTER – 2
SEISMIC ZONATION AND MICROZONATION
2.1. INTRODUCTION
India being a large landmass is particularly prone to earthquakes. Many disastrous earthquakes are experienced in the last decade in various parts of the Indian subcontinent. The distribution of the earthquakes occurrence is non-uniform throughout the country. The collision on the plate boundary between the Indian and Eurasian plate leads to the major earthquakes in India. The earthquakes are almost regular in the places in the northern, the northeastern and the northwestern part of India. But in the southern India the occurrence of earthquake is irregular. The Himalayan Frontier is seismically one of the most active regions of the world. The intensity and frequency of earthquake occurrence is not same in throughout the country. It varies depending upon the various factors such as geology, tectonics, soil types etc. Hence, it is very essential for classifying the entire country into different zones based on the seismicity of the
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The International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE, 1999) suggested some recommendations for seismic microzonation procedures. This paper examines the different methodologies and input data which are following the recommendation for the seismic microzonation. The different methodologies and basic principles presently used for the seismic microzonation map preparation are discussed in this paper. She concluded that by adopting the microzonation it is possible to carry out hazard related land use management which is very effective for reducing the seismic risk of an area. To perform the microzonation the inputs are required from various engineering fields such as geotechnical engineering and engineering geology. Nowadays various administrations are taking necessary steps to include seismic microzonation maps in their seismic codes, planning proceedings,
The earthquakes that have been considered are 1152, those for which a location was found in the catalogues: for 956 of them it was possible to calculate also, as additional information, the equivalent WA magnitude (MLBB). Indeed, since October 22, 2004 a Guralp 40-T BB seismometer with a period extended to 60 s was placed very close to the WA one. In addition, for 134 events recorded in the period 2010-2013 the equivalent ML was estimated both by the BB instruments placed at on the surface (MLBB) and at the bottom (MLTRI) of the cave (see Introduction). To compute the equivalent ML we have first deconvolved the BB instrument transfer function to obtain a ground displacement record and then we have convolved the signal with the WA transfer function.
These maps are referenced when updating building codes which are used by engineers and contractors when designing buildings, highways, bridges, and other structures to ensure they are built to withstand the effects of an earthquake should it hit the area. Other organizations, like insurance companies, FEMA, EPA, and AASHTO also reference these maps. (Earthquake Hazards, 2015) Uniform Building Code was established by the government to develop better building construction and ensure public safety. This is updated each year to ensure the safety regulations are as accurate as possible. Question Set 10 A)
Even though the standards are uniform in all counties and cities, both are permitted to include more restrictive regulations which could depend upon the weather, geological and topographical circumstances. These adoptions must nonetheless be documented and submitted to the commission. As areas and towns differ in conditions of topographical and geological circumstances the Title isn't too restrictive. These problems could be determined by a few factors like the place and its susceptibility to natural disasters such as mudslide, earthquakes or floods. Counties in areas exposed to earthquakes, for instance, restrict development of high rise structures.
Juneau is in a very unique situation. The city faces multiple geologic processes that could be dangerous. These processes can be very hazardous. Some of the hazards the city faces avalanches, earthquakes, heavy snow, landslides, and tsunamis. Although the city faces regular avalanches and the possibility of landslides the town’s major hazard is earthquakes.
When the mountainous area, such as Mnt. Triangle doesn 't get hit with such bad storms. The mountain, beings so tall kind of act as a shield to the land below it. The problem with the mountains, is that they are so tall so when an earthquake occurs the mountains will fall and destroy the area below.
This investigation developed the first comprehensive post-earthquake investigations. This investigation was chaired by Andrew Lawson among other geologists. This report offers a comprehensive understanding about the fields of geology, geodesy and seismology. The report also revealed the magnitude of damage within San Francisco and evidence of similar earthquakes in the past.
The text asserts that there were no sweeping fires to blame, only the earthquake. This event led to the first major legislative initiative in California to recognize seismic issues: the Field Act of 1933. Steinberg contends that although this was a step in the right direction, seismic enlightenment was still difficult. The author notes that regardless of awareness, many built in areas vulnerable to harmful seismic activity (i.e. near fault lines). The author also states that California is not the only area prone to earthquakes and that typically the poor suffer more from these events wherever they happen.
little movement from the tectonic caused big things such as earthquake, but what exactly is San Andreas Fault? San Andreas fault is major fracture of the Earth’s crust in extreme western north America (Brittanica). San Andreas fault have caused so many earthquakes in U.S.A, causing many destruction, and causing lost of lifes. Now, What made Northridge Earthquake so destructive? While the Northridge earthquake was happening Californian people couldn’t predict it (u-s-history.com).
Although the San Francisco Earthquake of 1906 and the Great Chicago Fire of 1871 were both horrific events that created huge destruction on the United States, they took a big toll in people’s lives in many different ways and encouraged them to take charge and rebuild back their hometowns that they loved. The San Francisco Earthquake commenced at five thirteen o’clock in the morning, with the epicenter offshore of San Francisco. The city carried more than 400,000 people during this event (Earthquake of 1906, 1). Most of the citizens who were present during the earthquake were all in bed asleep, but the early morning risers were able to witness the start of everything (The Great 1906, 5).
However, peculiarities of the lithosphere of the city can scare the newcomer. The city of San Francisco is in a high seismic activity zone, as very close are faults the San - Andreas (along the San Francisco Peninsula) and Hayward (on the eastern side of the bay). Small tremors come here often enough, but twice throughout its history (1906 and 1989) the city suffered the earthquake damage. The territory of San Francisco is a difficult terrain, as it has about fifty hills.
When was the first earthquake in North Carolina recorded? The first recorded earthquake was on March 8th, 1735 near Beth. Another one on February 21st, 1774 this one was quite noticeable speaking there were some reports from Winston Salem through Virginia. How do tsunamis form?
There are a lot of unexpected thing happened to our life. The Valdivia earthquake and Alaskan earthquakes is the most strongest earthquakes that ever happen in the world and this earthquakes are giving both of the two country a very big impact to their population and economy, they also losing a lot of people, housed, money and a huge of the area that earthquakes happened got damage. By the way one of the American author, Thomas Sowell, had said that “All thing are the same except for the differences and different except for the similarities” and that it true however both of them are the top strongest earthquakes but they are some different and similarity between them. Valdivia earthquake and Alaska earthquake are happened in America.
Since these tectonics plates are in the ocean, coasts have greater danger of being affected Costa Rica tends to experience more seismic activity in subduction zones. Earthquakes in these zones have been measured up to 8.5
Earthquakes are caused when rock underground suddenly breaks along a fault. This sudden release of energy causes the seismic waves that make the ground shake. When two plates are rubbing against each other, they stick a little. Most earthquakes occur along the edge of the oceanic and continental plates. Due to stress they shift and cause the earthquake.
” Earthquake is like a place with a lot of surprises, disaster that should be prepared. “Earthquakes are considered as one of the most destructive natural disasters and can produce many types of losses, including