Geophysics Geology 364

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GeophysicsGeology 364

• Introduction

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Exploration GeophysicsGeology 364
 An Introduction to Geophysical
Exploration Kearey, Brooks, and Hill 3rd Edition,
2002
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What is Geophysics?       

• A branch of experimental physics dealing with the
  earth, including atmosphere, hydrosphere, and
  lithosphere

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Solid Earth Geophysics

• Physical properties of Earth
• Gross Structure (materials, heat, pressure)
• Redistribution of Global materials
• Plate Tectonics
• EarthScope

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Exploration Geophysics

• Measures the physical properties of materials
  below the earths surface to detect or indicate
  the presence or location of ore bodies or
  hydrocarbons and geological structures

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Environmental Geophysics

• Characterization of surface and ground waters
• Organic and inorganic constituents
• Buried objects or voids

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Shallow Subsurface Geophysics

• Void detection (karst, tunnels, etc.)
• Buried utilities
• Construction conditions

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Borehole Geophysics

• Determination of materials and conditions in
  proximity of a borehole (down hole logging)

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Divining for minerals
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Early Attempts

• Chinese fortune tellers begin using loadstone to
  construct their divining boards, eventually
  leading to the first compasses. (Mentioned in
  Wang Ch'ung's Discourses weighed in the balance
  of 83 B.C.)
• Divining Rods to find more loadstone
• Magnetic compass used for iron prospecting as
  early as 1640 (dip needle)

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Brief Introduction to Geophysics

• Robert Fox discovered, in 1815, that certain
  minerals exhibit spontaneous polarization and
  proposed an exploration method.  
• Conrad Schlumberger, 1912 used basic equipment to
  map isopotential curves on family estate near
  Cean, France.
• In 1913 he  used spontaneous potential to locate
  a new metallic sulfide deposit at Bor 
  Yugoslavia. 
• 26 ore bodies, some dating to 4,500 BC
• Source of copper for tools and bronze

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Bor

• Type High-sulphidation epithermal
  massive-enargite (gold) sulphide deposits,
  porphyry Cu-Mo and Mo deposits
• Morphology
• Age of mineralization Upper/Late Cretaceous, 65
  4 Ma
• Ore minerals Enargite, pyrite, chalcopyrite,
  bornite, chalcocite, covellite, molybdenite,
  magnetite, pyrrhotite, galena, sphalerite, grey
  copper
• Alteration Silicification, argillic alteration,
  sericitization, chloritization, carbonatization
• Host rocks Andesite, volcaniclastic rocks,
  pyroclastic rocks
• Age of host rocks Upper/Late Cretaceous,
  Campanian, 78 4 Ma
• Host rock mineralogy Quartz, andesite, barite,
  pyrophyllite, diaspore, alunite, anhydrite,
  sulphur
• Mining Surface and underground mining
• Metals Cu, Au, Ag

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Conrad Schlumberger

• German geophysicist and petroleum engineer noted
  for the invention, in 1927, of a method of
  continuous electric logging of boreholes.
  Beginning1912, Conrad Schlumberger conceived the
  idea for electrical measurements to map
  subsurface rock bodies. He was joined by his
  brother, Marcel, in 1919. Schlumberger teams
  conducted geophysical surveys in Romania, Serbia,
  Canada, South Africa, Belgian Congo and the U.S.
  Electrical prospecting was used for the first
  time to map a subsurface oil-bearing structure -
  a salt dome in Romania. In 1927, the downhole
  electrical resistivity log was recorded in a well
  in Pechelbronn, France. Born 2 Oct 1878 died
  1936.

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Brief Introduction to Geophysics

• Pierre Bouguer, 1735, noted the amount of plumb
  deflection caused by particular peaks of the
  Andes.
• Sir George Everest, Surveyor-General of India, in
  the 1860s had a blown survey of a 365 mile-long,
  north-south line. there was a difference of 550
  feet between the direct triangulation and
  astronomic methods.  Error caused by the mass of
  the Himalayas.
• 1915-1916 torsion balance used to delineate salt
  dome oil field in Czechoslovakia.  Employed in
  1922 to locate salt domes in the Gulf Coast
  Region. By 1929 all of the piercement salt domes
  had been located by gravity surveys.

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Siesmics

• Chang Heng, astronomer
• royal to the Han Dynasty,
• invented an accurate
• seismograph in AD 132 It
• was a large bronze urn
• With eight dragon heads
• gazing outward in eight
• directions. Each dragon
• held a ball in his mouth.
• Around the base of the urn,
• under each dragon, sat a
• frog with his mouth open.

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Siesmics

• Rober Mallet, 1846, proposed to the Royal Irish
  Academy a method of obtaining subsurface
  information by artificial earthquakes
• In two years he developed a simple mercury-bowl
  seismoscope and measured the P-wave velocity of a
  granite by refraction.
• The First Principles of Observational Seismology
  (1862)

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Triode Vacuum Tube Amplifier
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Basic Triode Vacuum Tubes
6L6 and 807
B9A
WWII - 1968
1907 - 1929
1930 - WWII
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Siesmics

• In 1901, the Submarine Signal Company was formed
  and provided underwater signaling devices to the
  United States Lighthouse Service. In 1910, the
  brilliant Reginald Fessenden joined the company.
  He invented an oscillator in 1911 that he
  steadily improved. Within a few years, his
  massive 250kg transceiver went to sea on the U.S.
  Coast Guard Cutter MIAMI, and on April 27, 1914
  he was able to detect an iceberg over 20km away.
  While conducting this experiment, Fessenden, who
  was quite seasick, and his co-workers, Robert F.
  Blake and William Gunn, serendipitously noted an
  echo that returned about two seconds after the
  outgoing pulse. This turned out to be a return
  from the bottom. "Thus, on just one cruise....
  Fessenden demonstrated that both horizontal and
  vertical echoes could be generated within the
  sea..." (Bates et al. 1987).

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Vines Branch Experiment, 1921
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Basic Galvanometer 1905

• Analog Multimeter

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Induction Coil
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Basic Radio

• Simple Sparker
• All frequencies
• Lightning
• Sparker transmitters
• Early Wireless telegraphy
• Crystal Controlled
• Oscillator circuit (fixed frequency)

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AM Radio Signal
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Siesmics

• 1921 discovery of Orchard Dome, Texas by fan
  shooting
• 1927 First successful reflection profile

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• Seismics were developed in the 1920s    
  Refraction was most successful in locating
  non-piercement salt domes during the early 1920s.
• Reflection became routine in 1927.

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Very Early Reflection Seismogram
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Single Shot Analog Seismogram (1930s)
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Military and Early World War II Developments

• Pendulum Gravimeters - U-Boat location system
  with simple gravity map of Atlantic Ocean.
• Magnetic Mines - disturbance of ambient magnetic
  field.
• RADAR
• Magnetron Tube
• SONAR

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The original Mark I Magnetic Mine ('Type GA')
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Proximity Fuze- miniature RF         
transmitter-receiver-processor. 
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Computers

• Naval Fire Direction computers
• Enigma German code
• host of top mathematicians and general
  problem-solvers was recruited, and a bank of
  early computers, known as 'bombes', was built -
  to work out the vast number of permutations in
  Enigma settings.
• Magic (Japanese code breaking)

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Radar

• RAdio Detection And Ranging
• Magnatron Tube
• Ceramic and metal tube focus to produce a beam
• Microwaves
• Wavelength ltlt half the size of object!!!
• Reflection and Detection

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Early Computers

• ORDVAC
• ORDVAC was the first of two computers built under
  contract at the University of Illinois. ORDVAC
  was delivered to US Army Aberdeen Proving Grounds
  in the spring of 1951 and checked out in the
  summer. As part of the contract, funds were
  provided to the University of Illinois to build a
  second identical computer known as ILLIAC I.
• ILLIAC I
• ILLIAC I was the first electronic computer in the
  United states built and owned by a university. It
  was put on service on in 1952. It was built with
  2,800 vacuum tubes. ILLIAC I had a 5k main memory
  and 64k Drum memory..
• ILLIAC II
• The ILLIAC II was the first transistorized super
  computer. It was built by the University of
  Illinois. At its inception in 1958 it was 100
  times faster than competing machines of that day.
  It became operational in 1962, two years later
  than expected.
• ILLIAC II had 8192 words of core memory, backed
  up by 65,536 words of storage on magnetic drums.
  The core memory access time was 1.8 to 2 µS. The
  magnetic drum access time was 7 µS. A "fast
  buffer" was also provided for storage of short
  loops and intermediate results (similar in
  concept to what is now called cache). The "fast
  buffer" access time was 0.25 µS.
• The word size was 52 bits. Floating point numbers
  used a format with 7 bits of exponent (power of
  4) and 45 bits the mantissa. Instructions were
  either 26 bits or 13 bits long, allowing packing
  of up to 4 instructions per memory word.

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Transister 1947
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Tube vs Transistor Radios
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Digital Computation

• Binary Byte is basic unit (1101)
• Right Justified
• Two Bytes (10110011) 0 to F Hexadecimal
• Two Bytes 1 to 256
• Four Bytes 1 to 65,536

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Simple Integers in 2 byte (8 bits)
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Range of Numbers

• Integers
• 16 bits (4 bytes) -32,768 to 32,767
• 32 bits (8 bytes) -2,147,483,687 to 2,147,483,686
• Floating Points
• Precision is size of gap between numbers
• 32 bits
• 22 bit mantissa, 9 bit exponent, 1 bit sign

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Languages

• Assembly
• Compiler
• Operating Systems (DOS, OS1)
• Fortran, Basic, C, C, Cobal, Pascal
• Application

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Speed

• Integer calculations 200 to 2,000 times faster
  than floating point
• Addition twice as fast as subtraction
• Multiplication 100-1,000 time faster than
  division
• Transcendental functions real slow
• Many programs constrained by old operating systems