Many earthquakes are small and barely noticeable. Despite this devastation, earthquakes can also have positive benefits for humans.
Shaking, Landslides, Liquefaction, and Tsunamis Direct Shaking Hazards and Human-Made Structures Most earthquake-related deaths are caused by the collapse of structures and the construction practices play a tremendous role in the death toll of an earthquake.
In southern Italy in more thanpeople perished in an earthquake that struck the region. Almost half of the people living in the region of Messina were killed due to the easily collapsible structures that dominated the villages of the region.
A larger earthquake that struck San Francisco three years earlier had killed fewer people about because building construction practices were different type predominantly wood. Building practices can make all the difference in earthquakes, even a moderate rupture beneath a city with structures unprepared for shaking can produce tens of thousands of casualties.
Although probably the most important, direct shaking effects are not the only hazard associated with earthquakes, other effects such as landslides, liquefaction, Effects of earthquakes tsunamis have also played important part in destruction produced by earthquakes.
Geologic Effects on Shaking When we discussed earthquake intensity we discussed some of the basic factors that affect the amplitude and duration of shaking produced by an earthquake earthquake size, distance from fault, site and regional geology, etc.
The level of damage done to a structure depends on the amplitude and the duration of shaking. The amplitudes are largest close to large earthquakes and the duration generally increases with the size of the earthquake larger quakes shake longer because they rupture larger areas.
Regional geology can affect the level and duration of shaking but more important are local site conditions. Although the process can be complicated for strong shaking, generally shaking in soft sediments is larger and longer than when compared with the shaking experienced at a "hard rock" site.
Preparing Structures for Shaking The first step in preparing structures for shaking is to understand how buildings respond to ground motions- this is the field of study for earthquake and structural engineers.
When the ground shakes, buildings respond to the accelerations transmitted from the ground through the structure's foundation. The inertia of the building it wants to stay at rest can cause shearing of the structure which can concentrate stresses on the weak walls or joints in the structure resulting in failure or perhaps total collapse.
The type of shaking and the frequency of shaking depends on the structure.
Tall buildings tend to amplify the motions of longer period motions when compared with small buildings. Each structure has a resonance frequency that is characteristic of the building.
Predicting the precise behavior of buildings is complicated, a rule of thumb is that the period of resonance is about equal to 0. Thus Macelwane Hall resonates at about 0. Taller buildings also tend to shake longer than short buildings, which can make them relatively more susceptible to damage.
Fortunately many tall buildings are constructed to withstand strong winds and some precautions have been taken to reduce their tendency to shake. And they can be made resistant to earthquake vibrations.
The worst possible structure for earthquake regions is the unreinforced masonry which is common in the St. Estimating Hazards Preparing structures either new or old for earthquakes is expensive and the level of investment is a social and political decision. The choice of building design is a compromise between appearance, function, structure, strength, and of course, cost.
Standards are instituted through the establishment of Building Codes, which regulate the design and construction of buildings.
Most of our building codes are designed to protect first the building occupants, and second the building integrity. Building codes are usually drafted to meet the demands of the expected shaking in a given region that are summarized by seismologists and earthquake engineers in hazards maps.
Hazard maps are constructed by examining The earthquake history of the region to estimate the probability of an earthquake The expected shaking intensity produced by the earthquake often expressed as a peak acceleration The frequency of the shaking, the distance from the fault The regional geology and site conditions to estimate the maximum level of shaking expected during the lifetime of a building.Structural damage and fire.
Surface trembling from seismic waves often damages buildings.
A seiche is the effect of the sloshing of water back and forth. A seiche can be caused by an earthquake and/or a tsunami. The earthquake from Alaska on March 28th, caused seismic waves that were so powerful that bodies of water oscillated in many places across North America. What are the Harmful Effects of Earthquakes? (1) Damage to human structures – Earthquakes cause great damage to human structures such as buildings, roads, rails, factories, dams, bridges etc, and thus cause heavy damage to human property. Earthquake environmental effects are the effects caused by an earthquake, including surface faulting, tsunamis, soil liquefactions, ground resonance, landslides and ground failure, either directly linked to the earthquake source or provoked by the ground shaking.
Depending on the severity of the earthquake, gas mains may break, starting numerous fires. Foreshocks, small earthquakes that sometimes precede the main earthquake, can be .
There are other, secondary effects that are caused by earthquakes, most often a result of strong shaking. A simple example common in many earthquakes are landslides. The shaking causes regions of the rock and soil to slide downhill. The effects of an earthquake range from mild to severe and include structural damage, damaged gas lines, tidal waves, fires, avalanches and flooding.
The amount of damage an earthquake can cause depends greatly on the size of the earthquake. However, some earthquakes, such as Japan’s earthquake, can unleash devastating amounts of energy, killing thousands of people and destroying large areas of land. Despite this devastation, earthquakes can also have positive benefits for humans.
Earthquake: Earthquake, any sudden shaking of the ground caused by the passage of seismic waves through Earth’s rocks. Earthquakes occur most often along geologic faults, narrow zones where rock masses move in relation to one another.
Learn more about the causes and effects of earthquakes . What are the Harmful Effects of Earthquakes? (1) Damage to human structures – Earthquakes cause great damage to human structures such as buildings, roads, rails, factories, dams, bridges etc, and thus cause heavy damage to human property.