Reviewer introduction to exploration

3 internal divisions of earth

1. Crust

rich in silica, 38 km beneath continents and 7-8km beneath oceans. Identified by John Milne, Rutherford,

2. Mantle

2900km thick , rich in magnesium silica, discovery of Mohorovivic boundary which separates the crust and mantle

3. Core

predominantly iron, discovered by Odhom and delineated by Gutenberg.

inner core within the liquid outer core by Lehman.

Continental Drift -Alfred Wegener

Heliocentric - model proposed by Aristotle, wherein earth as the center.

Geocenteric - model proposed by copernicus, wherein sun as the center.

Astronomical unit (au) - 149,597,871 km mean radius of the earth's orbit around the sun.

Astrolabe - is an astronomical device used for star observation. Attributed to Hipparchus, and agular observations were converted to distances using the method of parallax.

Alidade - is a movable pointer at the center

Perihelion - near the sun , 147.1km

Aphelion - away from tbe sun, 152.1km.

Perigee - closest to the moon

Apogee - farthest from the moon

Galileo Galilei - first to hse telescope and discover the 4 largest satellite of the Jupiter.

Ganymede - largest moon, has magnetic field that causes auroras.

Callisto - mixture of icy and rocky surface, icy surface that is covered by craters, but no geological activities. Largest crater is also found which is the Valhalla crater.

Io - it is the most vocanically activite, rocky, with hundrends of volacanoes, its color is derived from sulfur dioxide and molten silicates.

Europa - smallest, has the smooth surface covered with ice.

Uranus- First planet discovered by a telescope, by William Hershel.

Neptune - due to orbits inconsistency it lead to the discover of Neptune.

Counterclockwise / Prograde - direction of the planet that revolve around the sun.

Prograde - direction of the rotation is the same as the directionof the orbit that is <90 .

Retrograde - direction of the rotation is opposite of the direction of the orbit that is > 90.

Bode's Law- used to determined the distances of planets from the sun.

8 mins 20 secs- time of suns light to reach earth

365.245 days - solar year

Obliquity - tilt of axis , with period of 41,000yrs, current obliquity is 23°26'21.4". Varies within 21.9° to 24.3° Summer solstice at maximum : june 21, winter solstice at minimum : dec. 21-22 .

Eccentricity - shape of the orbit ; ellipse shape. with period of 100,000 yrs.

Precession - wobble ,in retrograde motion with period of 21,000yrs.

present eccentricity - 0.017

Earth Mass - 5.9754 x10^24kg

Earth density - 5515 kg

earth quitorial radius - 6378 km

earth sidereal rotation - 0.9973

obliquity - 23.45°

Ceres,Vesta,Pallas, Juno - asteriods that are visible in the naked eye.

endogenic - internal origin : Volcanism and Tectonism

exogemic - external origin : Erosion and Deposition

Gondwanaland - Southern hemishere, Coined by Eduard Suess,

Laurasia- northern hemisphere

Tethys Sea - ses between gondwanaland and laurasi

Teiassic - start breaking up of africa and south america.

VGP (Virtual Paleomagnetic Pole position) - pole position at the time of formation of rock.

APW ( Apparent Polar Wander )- pole has shifted with time.

Vine-Matthews-Morley Hypothesis- explains the origin of magnetic anomaly patterns.

Triple Junctions - meeting of three plate boundaries. Has 16 types

Ridge (R) - in perpendicular

Transform Fault (F) - along the line

Trench (T) - parallel, depending on overriding plate.

Hooke's Law - Proportionality limit

Seismic waves - propagates through the body of the medium.

P waves(Longitudinal wave) - fastest, passes as series of dilatation and compression.

S waves (roational /equivoluminal) - travel slowly

Attenuation - decrease of amplitude with increasing distance from the source.

Surface waves (L) - spreads out over the surface

Rayleigh waves (Lr)- form retrograde ellipse

Love waves (Lq)- moves parallel

Huygens Principle - all points on wavefront can be regarded as point source.

Diffraction - occurs when waves encounter obstacles.

Fermat Principle- waves that follow path with the shortest travel time.

Subcritical Reflection - inside critical distance

Supercritical Reflection - beyond critical distance

Free Oscillations of the Earth - happens after a very large earthquake.

Normal modes- complicated type of vibration.

Nodes - points with zero displacements

Nodal surfaces- amplitude of the vibration is zero.

Radial oscillation - vibrate radially towards the center.

Spheroidal oscillation - twisting motion, both radial and tangential.

Toroidal oscillation- purely tangential, causes strain and displacement, can be recorded by strain seismometer.

Seismograph - is a device that can detect ground motion, invented by John Milne, uses concept of inertia.

Seismogram - visible record of earthquake.

Seismometer- is a sensor located inside the seismograph.

Geophone - term for exploration

Vertical seismometer- detect p waves

Horizontal seismometer - detect s waves

Strain seismometer - compsed of two rods,can record horizontal displacements, invented by H. Benioff.

Undamped - L=0 , cannot make an accurate record.

Critical damping - L=1, dont vibrate strongly, optimum behavior is 70% to 100%.

Overdamped- L>1, surpressed.

Long period sesimometer (displacement meter) - low frequency, small earthquake, 0.01-0.1Hz [10-100s]

Short period seismometer (accelerometer)- high frequency, large earthqauke, 1-10Hz[ 0.1-1s]

Broadband seismometer- large range of frequemcy / dynamic range, good for monitoring seismic hazards.

Galvanometer- used to convert electrical signal ro mechanical form.

Elastic Rebound model- proposed by H.F Reid, involves strain accumulation along fault lines.

ms- surface waves magnitude, used usually in >50 km focal depths

mb- to correct ms

seismic gaps- area that had been quiet for a long period of time, which might be accumulation of stress for future rupture. Also can help predicting where an earthquake would occur.

focus (hypocenter) stress released beneath surface.

epicenter- stress released above the focus.

Waddati Diagram - can calculate the epicentral distance.

Focal depths

•Shallow - 0-70km , 85% annualnejergy released

•Intermediate- 70-300km, 12%

•Deep- >300

Wadatti Benioff Zone- along subduction zone, discovered by Hugo Benioff and Kiyo Wadatti

Auxilary - perpendicular to fault line.

Global seimicity

• Circum Pacific zone - 75-70%

•Mediterranean-transasiatic zone - 15-20%

•Ocean ridges and rises - 7%

•Interplate earthquakes- 1%

Hydrostatic stress - same stress, causes change in volume

Deviatoric stress- not equal stress, causes distortion

Intensity - strength of earhauake perceived by people.

Magnitude -determined instrumentally.

Isoseimal maps- shows regional distribution of damage and important for assessing historical sesmicity of a region. Can contribute in making seismic risk maps.

Laser ranging -measure distance caused by the changes if cault movement.

Reflection seismology

•measures the travel time of reflecting waves, it is develop for petroleum exploration.

• uses geophones that is placed within subcritical reflection region.

Continuous Profiling- is is where the geophones are placed at discrete distances along the profile.

•Conventional coverage - sampling each reflection point at once.

↳split-spread method- geophoes are symmetrically arrange on either side of the shotpoint

the seismic wave recorded at any geophone below the point midway between the shot point and geophone. This is because seismic waves travel downward to reflector and then upward to geophone.

•Redundant coverage - sampling each reflection point multiple times.

↳common-midpoint method- repeatedly moving the shot shot point and geophone , signals are stacked to enhance signal to noise ratio. Travel times recorded by normal move out.

Migration - is the process in sesmic reflection that requires correction for nonvertical reflection.

Unmigrated section- reflection events are plotted vertically below control points on the surface, but it misrepresents the depth and dip of inclined reflectors.

Migrated section- has been corrected for nonvertical,reflections and provides a more accurate representation of subsurface reflector positions.

Uncorrected reflection- records make a tight syncline resemble a diffraction.

Synthetic seismograms- are computer generated representation of seismic waveforms, crucial for interpreting subsurface.

Groundroll- surface wave that interfere with subsurface relections.

Incoherent

Coherent

Multiple - common source of coherent noise, occur due to high reflection coefficients at the Earth's surface.

Seismic Refraction- the seismic disturbance travels just below the interface, where the velocity of the lower medium is higher.

This type of wave is called a head wave or Mintrop wave.

- The ray paths of these waves return to the surface at the critical angle within the region of supercritical reflections.

P - p wave

S - s wave

K - refracted in outer core

c - reflected in outer core

I - refracted in inner core

i - reflected in inner core