Introduction to GeophysicsAli Onceloncel@kfupm.edu.saDepartment of Earth SciencesKFU!Seismic Exploration: Fundamentals 3Previous Lecture"efracted "ay and An#le Ener#y "eturn and $ritical An#le%otal %ime of "efraction%ra&el %ime for Direct'"efracted (a&es Seismic "eflection Figure 3.30 of Lillie,199911ccccFigure 3.31 of Lillie,1999%rue )elocity and Apparent )elocity"efractedarri&als ha&e hi#her apparent &elocities than direct arri&als.ccFigure 3.33 of Lillie,1999Question: *afe+Drake $ur&es su##estin# that compressional ,a&e &elocity and density are directly proportional . %he -elo, e.uation/Implies that +,a&e &elocity is in&ersely proportionalto density0 E1plain the parado1.2ast 3ome,ork of the ,eekAnswer:Increasin# in seismic &elocity &ersus density is commonly true for rocks 4see *afe+Drake $ur&e50 e&en the a-o&e e.uation sho, an in&erse relation -et,een &elocity and density.As rocks -ecome more dense0 they -ecome more incompressi-le and more ri#id6 the correspondin# elastic constants 4k and 75 commonly increase more than the density 485.A ray incident on surface results in 9 reflected and refracted rays.If the seismic &elocities in medium : are ; < =.> km'sec0 ? < 9.@ km'sec0 ,hat are the seismic &elocities in medium AB(hat type of material is mediumABIdentify rays C:0 CA0 C90 CD asor S ,a&es. 3ome,ork Due to (ednesday12152035#1 #2 #3medium 1medium 2#4Solution for the 3ome,ork12152035#1 #2 #3medium 1medium 2#4 Vp = 6.5 km/sec Vs= 3.8 km/sec:. (hat could you say a-out in medium ABA5 )A E):F5 )AG):"emem-er that*o,0 you can conclude that )AG):%hen0 estimate the &elocities for t,o scenarios of incident ,a&es/ a5 +,a&eand -5 S+,a&e%hen0 estimate the an#les for either reflected or refracted.%hen0 compare ,hich ,a&e are #i&in# the an#les are #i&en in the ray tracin# model.%hen0 make a conclusion.P-waveS-waveP-waveP-wave"ock )elocities 4m'sec5pp. 18-19 of BergerSolution for the 3ome,orkUsin# the information in the -elo, fi#ures0E1plain the anomalous positions of )p and )s for ice. Anomalous positions of seismic velocity (! for ice occurs since t"e elastic mo#ules ($ an# %! increase more rapi#ly t"an &.%hese e1ercises are desi#ned to illustrates some of the -asic characteristics of ,a&e propa#ation in a sin#le layer model use ray+tracin# concepts to determine the arri&al times of particular e&ents. %hese e1ercises re.uire that you construct the time+distance plot for the #i&en model.In addition to constructin# the time+distance plots0Due to %uesdayI*%"ODU$%O"H "AH %"A$I*G EIE"$ISESGE*E"A2 I*S%"U$%IO*Shttp/'',,,.mines.edu'fsJhome't-oyd'G9::'!ODU2ES'SEIS'*O%ES'deri&:.htmlSin#le+2ayer !odelXVtdirect=1121212124VhVXtreflection+ =21222 1122 1V VV VhXVtrefraction +=E.uationsFe sure to do the follo,in#:5 la-el all plotted cur&es0A5 la-el all rele&ant points0 and95 in a para#raph or so discuss the si#nificanceand ori#ins of the interrelationships portrayed inthe resultant time+distance plotsParks and Plates2005 Robert J. LillieDepths in Kilometers