Question

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1)Can an earthquake's magnitude or intensity vary from place to place? Why?

2)Describe the difference between porosity and permeability

3)How can groundwater overdraft (groundwater withdrawal is greater than recharge) lead to land subsidence?

4)Philosophically, what is the difference between the uncertainty in the design factors of an engineered structure and the uncertainty of the geologic properties of the site where the structure will be located? How can the discrepancy between the two uncertainties be accommodated to insure a successful project?

Answer 1

1.

Yes an Earthquake's magnitude or intensity vary from place to place.

The intensity varies from place to place within the distributed region depending on the location of the observer with respect to the earthquake epicenter. Magnitude is related to the amount of seismic energy released at the hypocenter of the earthquake. This magnitude is represented by single instrumentally determined value.

2.

Porosity is a measure of how much open space is available of a rock. This space can be between grains or cavities of the rock.

Permeability is a measure of the ease with which a fluid can move through a porous rock.

3.

The process of extracting groundwater beyond the equilibrium yield of the aquifier is called overdrafting.

Natural process of recharge is done through percolation of surface water.

When ground water is exerted the water is primarily pulled from aquifier which creates cone depression around the well. When it continues cone depression increases in width. This increase leads to negative impacts caused by overdraftiing, such as drop of the water table,land subsidence.

4.

The detailed design of building needs to take into account various external factors, which may be subject to uncertainties. Among these factors are weather and climate, the properties of material used and the standard of workmanship.

And in case of geological properties the major problem during construction is ground behaving differently than anticipated. The nature of ground has significantly different implications for hand mining, drill and blast and tunnel boring operations.

These can be solved by proper surveying leveling of ground. Soil testing and design with respect to the topography of that place.