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Ali Oncel [email protected] .sa Department of Earth Sciences KFUPM Gravity Methods 3 F c Introduction to Geophysics troduction to Geophysics-KFUP

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Ali [email protected] of Earth SciencesKFUPMGravity Methods 3Introduction to GeophysicsIntroduction to Geophysics-KFUPMPrevious LectureGravity Methods 2Bouguer Correction Bouguer Gravity Anoa!y on Land Bouguer Gravity Anoa!y on "eaMid-#er $%aIntroduction to Geophysics-KFUPMGrade"tudentsGrade &istri'ution in Mid-#er $%a204317214269222736226202234345Introduction to Geophysics-KFUPMMid-Term Exam Solutions s m Vs m V/ 100002 . 02000/ 30004 . 0120021= == =1 22 112V VV Vh xcr+=3000 1000010000 30002 12001+=h7000130002 12001h =186 . 11200h = m h 3 . 4401 =h1XCRh1V1V21200 32000.40.6MetersSecondsV1, V2, h1?0.30.20.1Introduction to Geophysics-KFUPM"ip!i(ied version o( Assignent 2From Kearey, Brooks, and i!!, "##"Introduction to Geophysics-KFUPMFor e%ap!e) a dou'!e spi*e (unction) 2) +) , convo!ved -ith an ipu!se response (unction .) /) 2) , 0It -as c!ass e%ap!e o( Lecture 102 34+=pv=sv33/ 2950/ 95 . 2m kgcm g== GPa m kg s m vs04 . 43 ) / 2950) / 3820 3 2 2= = = GPaPa m kg s mv kP02 . 79) 10 ! 304 . 4 34) / 2950) / 6800 3410 3 22= = = Given that the P-ve!ocity o( a roc* is 203 *4s) the "-ve!ocity is /032 *4s) and density 2015 g4c/) ca!cu!ate 6 and *7 Introduction to Geophysics-KFUPMModi(ied version as*ed in 8ui9 ,:here possi'!e) supp!y the issing ;uantity in each case in the (o!!o-ing ta'!e) -here< i = ang!e o( incidence r = ang!e o( re(raction v, = -ave speed in upper !ayer) v2 = -ave speed in !o-er !ayer0 #he -ave originates in the upper !ayer0 Introduction to Geophysics-KFUPMModi(ied version as*ed in 8ui9 2#he sae ;uestion so!ved in C!ass211 12"= = =nii inii n rmst t v v$1%1# m s'1$"%"### m s'1$(%"()& m s'1t1%"*1) st"%1*"1 st(%1*1( svrs at the 'ase o( !ayer /7, -s064 . 188213 . 1 21 . 1 14 . 2) 13 . 1 2345) 21 . 1 2000) 14 . 2 1500 212 2 2=+ + + + Introduction to Geophysics-KFUPMvrs at the 'ase o( !ayer ,7, -s150014 . 2) 14 . 2 1500 212=, -s672 . 169721 . 1 14 . 2) 21 . 1 2000) 14 . 2 1500 212 2=+ + vrs at the 'ase o( !ayer 2729 . 0) 5 . 25 . 2 ) 02 . 27 . 1) 5 . 25 . 2 ) 02 . 27 . 11 1 2 21 1 2 212 ==+=v vv vR Introduction to Geophysics-KFUPM19 . 0) 02 . 27 . 1 ) 27 . 22 . 2) 02 . 27 . 1 ) 27 . 22 . 22 2 3 32 2 3 323==+=v vv vR Introduction to Geophysics-KFUPM024 . 0) 27 . 22 . 2 ) 28 . 23 . 2) 27 . 22 . 2 ) 28 . 23 . 23 3 4 43 3 4 434==+=v vv vR Introduction to Geophysics-KFUPM>eca!! GradingIntroduction to Geophysics-KFUPM?oe-or* "tatusIntroduction to Geophysics-KFUPM?oe-or* "tatusIntroduction to Geophysics-KFUPM?oe-or* "tatusIntroduction to Geophysics-KFUPM"uary o( $;uations (or Free Air and Bouguer Gravity Anoa!ies"tandard paraeters used to copute gravity anoa!ies on !and and at sea0FAC =Free-Air Correction@ BC =Bouguer Corrections@ BCs =Bouguer correction at seaA =reduction density@ h =e!evation BC and h- =-ater depth BCIntroduction to Geophysics-KFUPMBouguer Gravity Anoa!y on "eaIntroduction to Geophysics-KFUPMgfa= g gt + FACgB= gfa-BCBC= 0.419 hFC= h x !"#3"$ mGal%merrain CorrectionIntroduction to Geophysics-KFUPMgBC= gB'TCterrain correction is no needed in areas o( !o- re!ie( 'ut is re;uired -here changes in topography is signi(icant and e;uation (or a cop!ete Bouguer anoa!y is