Question
Please answer questions 1-12
Dynamic Eurth Exercise 16 Earthquakes In nature things moue violently to their place, and calnly in their place FRANCIS BACON Earthquakes are events within the earth that generate elastic waves. They are usually sudden displacements etermine the sense of motion of the rock masses to d that have moved. masses along faults, zones of weakness in the of rock crust. The waves from the disturbance propagate out- ward, transmitting the energy of the earthquake to To make these measurements requires a permanent record of the ground movements produced by the earthquake. Seismic waves are recorded by seismo- other parts of the earth. The particles of matter through graphs, instruments containing a heavy mass sus- such a way that its inertia keeps it relatively which the waves move simply vibrate back and forth pended i about their normal positions. This process is analo immobile gous to transmission of the energy of a storm to a distant shore by means of ocean waves. The water itself simply oscillates; only the energy of the wave is are amplified while the ground and the rest of the instru- ment vibrate. There are different ways to record the at sea vibrations, but in a fairly simpie system ground motions and recorded as a tine on a revolving drum. A continuous line that is drawn on the seis- ine that is draw Seismic rurves (from the Greek seisimos, shaking) may ograph paper as the drum revolves will appear as a vibrate back and forth in the directioni wave front travels, like sound waves. These are com from the drum. Figure 16.1B shows part of one line n which the sers of paralel lines after the paper has been removed They are called primary or P-waves of such a recording-a seonogram because they are the first to arrive from a distant earth- quake. Secondary or S-waves travel more slowl primary waves. In S-waves, the motion of particles is from side to s which the wave is traveling. These waves are analo-Epicenter gous in their motion to transverse light waves. Both types are illustrated in Figure 16.1 ide, perpendicular to the direction in On April 28, 1979, a moderate earthquake occurred in S- and P-waves are called body y waves because they northern California. Its seismic waves were recorded t travel through the interior of the earth. Their veloi- ties de perd n the compressibility, rigidity, and den- sity of the rocks through which they much on an extensive array of instruments, three of which are identified in Figure 16·met presents the- m Berkeley travel, and much mographic station on the University of California, has been learned about the interior structure of the earth through the study of the complex routes and ilton (Lick Observatory); and PCC is the one at Pilar- travel times of these waves. In a sense of earthquakes can be used to xray the earth, although seismograms obtained from this event at these three the images obtained are far from simple stations. Notice that the arrival of the P-wave is fol The first part of this laboratory exercise explores ome practical aspects of seismology -how to deter moving S-wave. The farther the recording station is mine the epicenter (the point on the earth's surface from the epicenter of the earthquake, the greater is directly above the origin of the earthquake), the origin the difference between P- and S-wave arrival times. time, and the magnitude of an earthquake, and how This feature may be used to cakculate epicentral dis- 272
Explanation / Answer
Answer:1
At 3:45:00pm (given in figure) P wave reached MHC.
Answer:2
As S wave is slower than P wave, therefore, It reached later than P wave by 10second means , 3:55:10 pm.
Answer:3
There is difference between of 10seconds between P wave and S wave.
Answer:4
Epicenter to BRK= 130km
Epicenter to MHC= 100km
Epicenter to PCC= 120km
Answer:5
Draw the circle of radius (answer:4) of above stations.
Answer:6
As where the circles cuts each other at one common point, this is the epicenter of earthquake.