Sedimentary or metamorphic rocks and engineering issues - Essay Example

Sedimentary Rocks and Earthquake Intensity: A Report to the Department of Natural Resources al Affiliation Sedimentary Rocks and Earthquake Intensity: A Report to the Department of Natural ResourcesOne of the characteristics of the 20th and the 21st century is the increase in earthquakes in various parts of the world. Unlike past earthquakes, recent earthquakes are characterized by high shaking intensities and huge damages and devastations of economies. As a result, anything that can trigger earthquakes or anything that can increase their intensity needs to be highly observed.

One of the major parameters that affect an earthquake’s shaking intensity is the physical parameter, which includes such things as soil types and rock types (Monroe & Wicander, 2001).  Given the ability of engineers to measure all these, an emphasis on the latter is quite important in order to provide insight that would at least help in reducing earthquake intensities in the society. Particularly, the understanding of sedimentary rocks and their contribution to earthquakes intensities is necessary.

Nature of Earthquake IntensityTo start with, earthquake shaking starts from the rupturing fault and then continues at other distances away from the fault. Earthquake shaking intensity is supposed to decrease as the distance from the rupturing fault decreases. However, it has been observed that shaking in one site is sometimes stronger than shaking in another site. Sometimes, this shaking can be ten times higher or stronger than shaking in another site (Ammon, 1997). Sedimentary Rocks and Earthquake IntensityGeologists have come up with information relating sedimentary rocks with earthquake shaking intensities.

Geologists argue that shaking is always high in areas of softer rocks. In addition, shaking is amplified in areas of thicker sediments compared to areas of thin sediments. As it has been observed, the major reason why sedimentary rocks are associated with shaking intensities is because they are soft (Denecke & Series, 2003). An explanation of the relationship between sedimentary rocks and earthquakes shows that seismic waves’ speed is much higher in hard rocks when compared to sedimentary rocks.

This is because the latter are soft as it has been explained earlier. In areas with different rock types, waves tend to pass through harder rocks to the softer rocks, they slow down. However, in order to carry the same energy carried in the hard rocks, they tend to get bigger than before. Therefore, shaking at sites that have soft rock layers is stronger since the seismic waves tend to move slowly as shown in Figure 1 and 2 (SCEC, 2014). Figure 1: Seismic Waves in Hard Rocks (SCEC, 2014)Figure 2: Seismic Waves in Soft Rocks (SCEC, 2014)How to deal with Sedimentary Rocks’ Effect and Earthquake IntensityThe loss of life and properties associated with earthquake intensities can actually be controlled by avoiding buildings in area of soft sedimentary rocks.

If this is not so, the society, governments and the concerned parties need to prepare for earthquakes by understanding the intensity that an earthquake can hit in a particular area. This means that knowledge about the source of earthquake or the fault that triggers the earthquake is not as important as knowing the geologic condition of all areas and intensity related to this geologic condition (SCEC, 2014).ConclusionIn conclusion, sedimentary rocks unlike other rocks are soft. As a result, these rocks tend to increase the rate of seismic waves causing more damaging earthquakes in areas of high population.

As a result, knowing the rock type before constructions is important in dealing with the high detrimental effects of earthquakes.ReferencesDenecke, E., & Series, I. (2003). Barrons regents exams and answers: Earth science : The physical setting. Hauppauge, N.Y.: Barrons Educational Series.Monroe, J., & Wicander, R. (2001). The changing earth: Exploring geology and evolution (3rd ed.). Pacific Grove, CA: Brooks/Cole.Ammon, C. (1997). “Early observation of earthquakes-shaking intensity.” Department of Geosciences.

Retrieved on Nov 23, 2014 from: http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/IntroQuakes/Notes/intensity.htmlSCEC (2014). “Earthquake shaking-accounting for site effects.” South California Earthquake Center. Retrieved on Nov 23, 2014 from: http://www.scec.org/phase3/overview.html