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GPH 444

Marine Geophysics

(Unit 1)

Credits:

2 hours (2+0+0)

Reference Book:

ͻMarine Geophysics. E. J. W.

Jones (1999), Wiley.

ͻApplied High-Resolution

Geophysical Methods.

Offshore Geoengineering

Hazard (1984). Peter K.

Trabant, International Human

Resources Development

Corporation.

GPH 444: Unit 1 (Introduction)

Course Topics:

Unit 1: Introduction. Unit 2: Marine Science. 1 st Exam Unit 3: Marine Geotechnics. Unit 4: Echo Sounders. 2 nd Exam Unit 5: Side Scan Sonar. Unit 6: Marine Magnetometers. 3 rd Exam

GPH 444: Unit 1 (Introduction)

Grading:

1 st Exam 20% 2 nd Exam 20% 3 rd Exam 20%

Final Exam 40%

GPH 444: Unit 1 (Introduction)

Attendance:

-Never to be late more than (10) minutes. -Never play with your cell phone. -Never talk to your friend. -Never miss more 25% of the total lectures.

Participation:

-Involve in all group discussions and activities. -Write down all important information in your notebook.

GPH 444: Unit 1 (Introduction)

Join a study group.

Make study schedule.

Arrange your time.

Do your best.

Seek advice.

Learn from mistakes.

Be patient.

GPH 444: Unit 1 (Introduction)

Learning Objectives By the end of unit (1) you should be able to recognize:

1. Earth's internal structure.

2. The difference between continental crust and

oceanic crust.

3. Plate tectonic theory.

4. Types of plate boundaries.

5. How, where, and why earthquakes occur.

6. Wadati-Benioff zone.

7. Types & depths of earthquakes.

8. How to measure an earthquake.

9. The definition of geophysics.

10 . Types of seismic waves.

GPH 444: Unit 1 (Introduction)

Rocks of the crust provide clues to Earth"s past. By analyzing these clues we can infer events from the past.

GPH 444: Unit 1 (Introduction)

Earth radius is the distance from Earth"s center to its .km6378 surface which is about

GPH 444: Unit 1 (Introduction)

Definitions

Earthquake: Vibration of the Earth produced by the rapid release of energy.

Seismic waves:

Energy moving outward from the focus of an earthquake. Focus (hypocenter): Location of initial slip on the fault; where the earthquake origins.

Epicenter:

Spot on Earth"s surface directly above the focus.

GPH 444: Unit 1 (Introduction)

Types of Earthquakes: The type of earthquake depends on the region where it occurs and the geological make -up of that region.

1. Tectonic Earthquakes: these occur when rocks in the

earth's crust break due to geological forces created by movement of tectonic plates.

2. Volcanic Earthquakes: occur in conjunction with

volcanic activity.

3. Collapse Earthquakes: are small earthquakes in

underground caverns and mines.

4. Explosion Earthquakes: result from the explosion of

nuclear and chemical devices.

GPH 444: Unit 1 (Introduction)

Depth of Earthquakes:

1. Shallow earthquakes:

(Depth between 0 and 70 km).

2. Intermediate earthquake:

(Depth between 70 and 300 km).

3. Deep earthquakes:

(Depth is greater than 300 km).

GPH 444: Unit 1 (Introduction)

Measuring Earthquakes:

Seismometers:

instruments that detect seismic waves.

Seismographs:

Record intensity,

height and amplitude of seismic waves.

GPH 444: Unit 1 (Introduction)

Geophysics: is the science which deals with investigating the earth, using the methods and techniques of physics.

GPH 444: Unit 1 (Introduction)

Geophysics = Geological Observations + Physical Laws

GPH 444: Unit 1 (Introduction)

Waves of energy that travel through the Earth's layers, and are a result of an earthquake, explosion, or a volcano.

GPH 444: Unit 1 (Introduction)

S-waves

Transverse.

Slow moving.

Travel through solids only.

P-waves

Longitudinal.

Fast moving.

Travel through liquids and

solids.

GPH 444: Unit 1 (Introduction)

Compressional Waves: Shear Waves:

Relationship between Vp and Vs:

ͻAveraged Vp/Vs = 1.732 for the crust.

ͻFor mafic rocks, Vp/Vs = 1.81.

ͻFor felsic rocks, Vp/Vs = 1.70.

GPH 444: Unit 1 (Introduction)

ϰϰϰ

ĂƌŝŶĞĞŽƉŚǇƐŝĐƐ

;ŶŝƚϮͿ

ĞĂƌŶŝŶŐďũĞĐƚŝǀĞƐ

ǇƚŚĞĞŶĚŽĨƵŶŝƚ;ϮͿǇŽƵƐŚŽƵůĚďĞĂďůĞƚŽƌĞĐŽŐŶŝǌĞ͗ϭ͘ŚĞĚĞĨŝŶŝƚŝŽŶŽĨŽĐĞĂŶŽŐƌĂƉŚǇĂŶĚŝƚƐĚŝǀŝƐŝŽŶƐ͘

Ϯ͘ŽůĞŽĨŽĐĞĂŶƐ͘ ϯ͘ŽǁƚŽƐƚƵĚǇŽĐĞĂŶƐ͘

ϰ͘ŶƐƚƌƵŵĞŶƚƐŽĨŝŶǀĞƐƚŝŐĂƚŝŽŶ͘

ϱ͘ƌŝǀŝŶŐĨŽƌĐĞƐΘƉƌŽĐĞƐƐĞƐŽĨĞǀŽůƵƚŝŽŶŽĨŽĐĞĂŶ

ĨůŽŽƌ͘

ϲ͘ŝůƐŽŶǇĐůĞ͘

ϳ͘ĂƚŚǇŵĞƚƌǇ͘

ϴ͘ŝǀŝƐŝŽŶƐŽĨŽĐĞĂŶĨůŽŽƌ͘

ϵ͘ůĂƐƐŝĨŝĐĂƚŝŽŶŽĨĐŽŶƚŝŶĞŶƚĂůŵĂƌŐŝŶƐ͘

ϭϬ͘ĐĞĂŶďĂƐŝŶΘŵŝĚͲŽĐĞĂŶŝĐƌŝĚŐĞ͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ĐĞĂŶсƚŚĞŵĂƌŝŶĞĞŶǀŝƌŽŶŵĞŶƚ

ŐƌĂƉŚǇ сƚŚĞŶĂŵĞŽĨĂĚĞƐĐƌŝƉƚŝǀĞƐĐŝĞŶĐĞ

ĐĞĂŶŽŐƌĂƉŚǇŝƐƚŚĞƐĐŝĞŶƚŝĨŝĐ͗ĞĨŝŶŝƚŝŽŶ

ƐƚƵĚǇŽĨĂůůĂƐƉĞĐƚƐŽĨƚŚĞŵĂƌŝŶĞ

ĞŶǀŝƌŽŶŵĞŶƚ͘

ĐĞĂŶŽŐƌĂƉŚǇсĐĞĂŶŽůŽŐǇсĂƌŝŶĞĐŝĞŶĐĞ

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ĂƌŝŶĞĐŝĞŶĐĞƚƵĚǇ͗ϭ͘ŚĞǁĂƚĞƌŽĨƚŚĞŽĐĞĂŶ͘Ϯ͘ŚĞůŝĨĞǁŝƚŚŝŶƚŚĞŽĐĞĂŶ͘ϯ͘ŚĞƐŽůŝĚĂƌƚŚďĞŶĞĂƚŚƚŚĞŽĐĞĂŶ͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ŝǀŝƐŝŽŶƐŽĨĐĞĂŶŽŐƌĂƉŚǇ͗ϭ͘ĞŽůŽŐŝĐĂůĐĞĂŶŽŐƌĂƉŚǇ;ĂƌŝŶĞĞŽůŽŐǇͿ͗ƐƚƵĚǇƚŚĞƐƚƌƵĐƚƵƌĞŽĨƐĞĂĨůŽŽƌ͘

Ϯ͘ŚĞŵŝĐĂůĐĞĂŶŽŐƌĂƉŚǇ;ĂƌŝŶĞŚĞŵŝƐƚƌǇͿ͗

ƐƚƵĚǇƚŚĞĐŚĞŵŝĐĂůĐŽŵƉŽƐŝƚŝŽŶĂŶĚƉƌŽƉĞƌƚŝĞƐŽĨƐĞĂǁĂƚĞƌ͘ϯ͘ŚǇƐŝĐĂůĐĞĂŶŽŐƌĂƉŚǇ;ĂƌŝŶĞŚǇƐŝĐƐͿ͗ƐƚƵĚǇƚŚĞǁĂǀĞƐ͕ƚŝĚĞƐ͕ĂŶĚĐƵƌƌĞŶƚƐ͘ϰ͘ŝŽůŽŐŝĐĂůĐĞĂŶŽŐƌĂƉŚǇ;ĂƌŝŶĞŝŽůŽŐǇͿ͗ƐƚƵĚǇƚŚĞŽĐĞĂŶůŝĨĞ͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ŽǁƚŽƚƵĚǇĐĞĂŶƐ͗ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ϭ͗͘ŝƐĂĞůĨͲŽŶƚĂŝŶĞĚŶĚĞƌǁĂƚĞƌƌĞĂƚŚŝŶŐƉƉĂƌĂƚƵƐ͘ĂŶŬƐŽĨĐŽŵƉƌĞƐƐĞĚĂŝƌ

ƐƚƌĂƉƉĞĚŽŶĂĚŝǀĞƌ͛ƐďĂĐŬĂŶĚĐŽŶŶĞĐƚĞĚďǇ

ŚŽƐĞƐƚŽĂŵŽƵƚŚƉŝĞĐĞĨŽƌďƌĞĂƚŚŝŶŐ͘

ŶǀĞƐƚŝŐĂƚŝŽŶ͗ŽĨŶƐƚƌƵŵĞŶƚƐ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ŶǀĞƐƚŝŐĂƚŝŽŶ͗ŽĨŶƐƚƌƵŵĞŶƚƐ

Ϯ͗͘ŝƐĂŽƵŶĚĂǀŝŐĂƚŝŽŶŶĚĂĚĂƌ͘ĞƚŚŽĚƐŽĨŵĂƉƉŝŶŐƚŚĞŽĐĞĂŶĨůŽŽƌďǇ

ƚƌĂŶƐŵŝƐƐŝŽŶĂŶĚƌĞĨůĞĐƚŝŽŶŽĨƐŽƵŶĚǁĂǀĞƐ͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ŶǀĞƐƚŝŐĂƚŝŽŶ͗ŽĨŶƐƚƌƵŵĞŶƚƐ

ϯ͘ĞŽƐƚĂƚŝŽŶĂƌǇƉĞƌĂƚŝŽŶĂůŶǀŝƌŽŶŵĞŶƚĂůĂƚĞůůŝƚĞƐ;Ϳ͗ŽƌďŝƚƚŚĞĂƌƚŚĂƚϮϮ͕ϬϬϬŵŝůĞƐ͘ŚĞǇĂƌĞŚŝŐŚůǇĂĚǀĂŶĐĞĚŽďƐĞƌǀĂƚŝŽŶƉůĂƚĨŽƌŵ

ƐƵƉƉůǇŝŶŐĚĞƚĂŝůĞĚŝŵĂŐĞƌǇŽĨƚŚĞĂƌƚŚ͛ƐŽĐĞĂŶƐ

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ϰ͘ĞĞƉĐĞĂŶƵďŵĞƌƐŝďůĞƐ͗ǀĞƌƚŚĞůĂƐƚĨĞǁĚĞĐĂĚĞƐ͕ĞŶŐŝŶĞĞƌƐŚĂǀĞĚĞǀĞůŽƉĞĚƚĞĐŚŶŽůŽŐŝĞƐ

ĐĂƉĂďůĞŽĨŵĞĞƚŝŶŐƚŚĞŵĂŶǇĐŚĂůůĞŶŐĞƐƚŚĂƚƚŚĞ

ĚĞĞƉƐĞĂŝŵƉŽƐĞƐƵƉŽŶĞǆƉůŽƌĞƌƐ͘

ŶǀĞƐƚŝŐĂƚŝŽŶ͗ŽĨŶƐƚƌƵŵĞŶƚƐ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ĐĞĂŶĨůŽŽƌŝƐƚŚĞďŽƚƚŽŵŽĨƚŚĞŽĐĞĂŶ;ƐƚƌƵĐƚƵƌĞƐΘĨĞĂƚƵƌĞƐͿ͘

;ĐĞĂŶĨůŽŽƌсĞĂĨůŽŽƌсĞĂĨůŽŽƌсĞĂďĞĚͿ

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ŝůƐŽŶǇĐůĞ͗

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ĂƚŚǇŵĞƚƌǇ

;ďĂƚŚǇсĚĞƉƚŚ͕ŵĞƚƌǇсŵĞĂƐƵƌĞŵĞŶƚͿ

ĂƚŚǇŵĞƚƌǇŝƐƚŚĞŵĞĂƐƵƌĞŵĞŶƚŽĨŽĐĞĂŶĚĞƉƚŚƐĂŶĚƚŚĞ

ĐŚĂƌƚŝŶŐŽĨƚŚĞƐŚĂƉĞŽƌƚŽƉŽŐƌĂƉŚǇŽĨƚŚĞŽĐĞĂŶĨůŽŽƌ

͘ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ůŽŽƌ͗ŝǀŝƐŝŽŶƐŽĨĐĞĂŶ ϭ͘ ŽŶƚŝŶĞŶƚĂůĂƌŐŝŶƐ͘ Ϯ͘ ĞĞƉͲŽĐĞĂŶĂƐŝŶƐ͘ ϯ͘ ŝĚͲŽĐĞĂŶŝĚŐĞ͘ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ŽŶƚŝŶĞŶƚĂůĂƌŐŝŶƐ͗

ŽŶƚŝŶĞŶƚĂůŵĂƌŐŝŶƐĂƌĞƐŚĂůůŽǁͲǁĂƚĞƌĂƌĞĐůŽƐĞƚŽ

ĐŽŶƚŝŶĞŶƚƐ͘ ŚĞǇĂƌĞƚŚĞǌŽŶĞŽĨƚŚĞŽĐĞĂŶĨůŽŽƌƚŚĂƚ

ƐĞƉĂƌĂƚĞƐƚŚĞƚŚŝŶŽĐĞĂŶŝĐĐƌƵƐƚĨƌŽŵƚŚŝĐŬĐŽŶƚŝŶĞŶƚĂů

ĐƌƵƐƚ͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ůĂƐƐŝĨŝĐĂƚŝŽŶƐŽĨŽŶƚŝŶĞŶƚĂůĂƌŐŝŶƐ͗

ϭ͘ ĂƐƐŝǀĞĂƌŐŝŶƐ͗ĂƌĞůŽĐĂƚĞĚĂƚƚŚĞ

ƚƌĂŶƐŝƚŝŽŶďĞƚǁĞĞŶŽĐĞĂŶŝĐĂŶĚĐŽŶƚŝŶĞŶƚĂů

ĐƌƵƐƚǁŚŝĐŚŝƐŶŽƚĂŶĂĐƚŝǀĞƉůĂƚĞŵĂƌŐŝŶ͘

Ϯ͘ ĐƚŝǀĞĂƌŐŝŶƐ͗ĂƌĞƚŚŽƐĞƚŚĂƚĂƌĞ

ƚĞĐƚŽŶŝĐĂůůǇĂĐƚŝǀĞ͕ƐƵĐŚĂƐĂůŽŶŐŵƵĐŚŽĨ

ƚŚĞĂĐŝĨŝĐĐŽĂƐƚ͘ ϭ͘ ŽŶǀĞƌŐĞŶƚĐƚŝǀĞĂƌŐŝŶƐ ͘ Ϯ͘ ƌĂŶƐĨŽƌŵĐƚŝǀĞĂƌŐŝŶƐ͘ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ŽŶƚŝŶĞŶƚĂůŚĞůĨ͗

ŽŶƚŝŶĞŶƚĂůƐŚĞůĨŝƐĂĨůĂƚǌŽŶĞĞǆƚĞŶĚŝŶŐĨƌŽŵƚŚĞƐŚŽƌĞ

ďĞŶĞĂƚŚƚŚĞŽĐĞĂŶƐƵƌĨĂĐĞƚŽĂƉŽŝŶƚĂƚǁŚŝĐŚĂŵĂƌŬĞĚ

ŝŶĐƌĞĂƐĞŝŶƐůŽƉĞĂŶŐůĞŽĐĐƵƌ͕ĐĂůůĞĚƚŚĞƐŚĞůĨďƌĞĂŬ͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ŽŶƚŝŶĞŶƚĂůůŽƉĞ͗

ŽŶƚŝŶĞŶƚĂůƐůŽƉĞŝƐǁŚĞƌĞƚŚĞĚĞĞƉͲŽĐĞĂŶďĂƐŝŶƐďĞŐŝŶ͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ŽŶƚŝŶĞŶƚĂůŝƐĞ͗

ŽŶƚŝŶĞŶƚĂůƐůŽƉĞŝƐĂƚƌĂŶƐŝƚŝŽŶǌŽŶĞďĞƚǁĞĞŶƚŚĞ

ĐŽŶƚŝŶĞŶƚĂůŵĂƌŐŝŶĂŶĚƚŚĞĚĞĞƉͲŽĐĞĂŶĨůŽŽƌ͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ĐĞĂŶĂƐŝŶ͗

ĐĞĂŶďĂƐŝŶƐĂƌĞůĂƌŐĞŐĞŽůŽŐŝĐďĂƐŝŶƐƚŚĂƚĂƌĞďĞůŽǁ

ƐĞĂůĞǀĞů͘

ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ŝĚͲĐĞĂŶŝĐŝĚŐĞ͗ ŵŝĚͲŽĐĞĂŶƌŝĚŐĞŝƐĂ ŐĞŶĞƌĂůƚĞƌŵĨŽƌĂŶ ƵŶĚĞƌǁĂƚĞƌŵŽƵŶƚĂŝŶ ƐǇƐƚĞŵƚŚĂƚĐŽŶƐŝƐƚƐŽĨ ǀĂƌŝŽƵƐŵŽƵŶƚĂŝŶƌĂŶŐĞƐ ;ĐŚĂŝŶƐͿĨŽƌŵĞĚďǇƉůĂƚĞ

ƚĞĐƚŽŶŝĐƐ͘

ŚŝƐƚǇƉĞŽĨŽĐĞĂŶŝĐƌŝĚŐĞŝƐĐŚĂƌĂĐƚĞƌŝƐƚŝĐŽĨǁŚĂƚŝƐŬŶŽǁŶĂƐĂŶŽĐĞĂŶŝĐƐƉƌĞĂĚŝŶŐĐĞŶƚĞƌ͕ǁŚŝĐŚŝƐ

ƌĞƐƉŽŶƐŝďůĞĨŽƌ

ƐĞĂĨůŽŽƌ

ƐƉƌĞĂĚŝŶŐ

͘ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ ϰϰϰ͗ŶŝƚϮ;ĂƌŝŶĞĐŝĞŶĐĞͿ

ϰϰϰ

ĂƌŝŶĞĞŽƉŚǇƐŝĐƐ

;ŶŝƚϯͿ

ĞĂƌŶŝŶŐďũĞĐƚŝǀĞƐ

ǇƚŚĞĞŶĚŽĨƵŶŝƚ;ϯͿǇŽƵƐŚŽƵůĚďĞĂďůĞƚŽƌĞĐŽŐŶŝǌĞ͗ϭ͘ĂƌŝŶĞŐĞŽƉŚǇƐŝĐĂůƐƵƌǀĞǇŵĞƚŚŽĚƐ͘

Ϯ͘ĞĂďĞĚ;ƐƵďͲƐƵƌĨĂĐĞͿŐĞŽƉŚǇƐŝĐĂůƐƵƌǀĞǇƐ͘

ϯ͘ĞĂďĞĚĐŚĂƌĂĐƚĞƌŝƐƚŝĐ͘ ϰ͘ĞǀĞůŽƉŵĞŶƚƉƌŽĐĞƐƐ͘

ϱ͘ĞƐŬƐƚƵĚǇ͘

ϲ͘ŝůΘŐĂƐŽĨĨƐŚŽƌĞƐƚƌƵĐƚƵƌĞ͘

ϳ͘ĂƌŝŶĞǀĞƐƐĞů͘

ϴ͘ŶŐŝŶĞĞƌŝŶŐŚǇĚƌŽŐƌĂƉŚŝĐΘŐĞŽƉŚǇƐŝĐĂůŽƉĞƌĂƚŝŽŶƐ͘

ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ ϰϰϰ͗Ŷŝƚϯ;ĂƌŝŶĞĞŽƚĞĐŚŶŝĐƐͿ

GPH 444

Marine Geophysics

(Unit 4) Learning Objectives By the end of unit (4) you should be able to recognize: 1 . Basic physics. 2 . Underwater sound 3 . Sound refraction. 4 . Coastal variability. 5 . Active & passive sonar. 6 . Range estimation.

7. Echo sounders.

8. Properties in a sonar image.

9. Characteristic of sound in sea water.

10 . Factors affecting choose of frequency. 11 . Principle of echo sounder. 12 . Reason for using sound waves.

GPH 444: Unit 4 (Echo Sounders)

Characteristic of Sound in Sea Water:

a) Speed of sound: The speed of sound in sea water varies throughout the world with temperature, pressure due to depth, and salinity. An increase in any of these factors will cause an increase in speed of sound and vice versa. Even in the same place, temperature and salinity vary not only with depth but also from hour to hour. The speed of sound can vary from about

1445 m/s to 1535 m/s.

GPH 444: Unit 4 (Echo Sounders)

Characteristic of Sound in Sea Water:

b) Spreading loss of sound in sea water: When sound is propagated into sea water the intensity decreases due to spreading. The actual intensity corresponds to power per unit area of cross section of wave front. The beam spreads out according to an inverse square rule.

GPH 444: Unit 4 (Echo Sounders)

Characteristic of Sound in Sea Water:

c) Attenuation (Absorption of sound in sea water): As an acoustic wave propagates through sea water all of its energy ultimately converts to the heat due to viscosity and relaxation efforts.

GPH 444: Unit 4 (Echo Sounders)

d) Volume reverberation: When acoustic energy is propagated into sea water continuous returned echoes at the same frequency as the transmission are produced by back scattering from minute air bubbles, planktons, pollution, suspended sand and other discontinuities in the water. This is termed a volume reverberation signal and its magnitude increases dramatically with frequency.

Characteristic of Sound in Sea Water:

GPH 444: Unit 4 (Echo Sounders)

In coastal regions the volume reverberation signal is high due to large concentrations of continental dust, pollution, plankton and small air bubbles. In mid ocean regions the scarcity of dust and pollution gives a reduced volume reverberation signal. In tropical mid ocean regions the disappearance of plankton results in a very low volume reverberation signal.

Characteristic of Sound in Sea Water:

GPH 444: Unit 4 (Echo Sounders)

Factors Affecting Choose of Frequency:

1)Size and cost: Lower the frequency, larger and costlier

the transducer.

2) Minimum attenuation (absorption):

Higher the

frequency (especially greater than 100 kHz), greater amount of absorption.

3) Minimum volume reverberation (for echo sounders)

and more volume reverberation (for Doppler water speed logs): Higher frequency, greater amount of reverberation.

4) Free from ship noise (self-noise and ambient noise):

Amount of noise is more at lower frequencies.

GPH 444: Unit 4 (Echo Sounders)

Echo sounders measure water depth by sending acoustic pulses through a transducer and picks up the reflected echoes. The depth is calculated from the two way travel time of the velocity of sound in water. As the vessel moves a single beam echo sounder (SBES) repeatedly "ping" the seafloor with a sound pulse, producing a discrete print of depths beneath the ship.

GPH 444: Unit 4 (Echo Sounders)

GPH 444

Marine Geophysics

(Unit 5) Learning Objectives By the end of unit (5) you should be able to recognize: 1 . Components of an echo event at the sea floor. 2 . Principles of side scan sonar. 3 . Typical echo sounder output. 4 . Sonograph characteristics.

5. Side scan sonar geometry.

6 . Target material and orientation influences. 7 . Vessel speed effects.

8. Types of side scan sonar.

9 . Limitation of side scan sonar.

GPH 444: Unit 5 (Side Scan Sonar)

Components of an Echo Event at the Sea Floor

Incident energy is partitioned between transmission into the sea floor and the echo, which is both reflection and scattering back into the water

GPH 444: Unit 5 (Side Scan Sonar)

ϰϰϰ

ĂƌŝŶĞĞŽƉŚǇƐŝĐƐ

;ŶŝƚϲͿ

ĞĂƌŶŝŶŐďũĞĐƚŝǀĞƐ

ǇƚŚĞĞŶĚŽĨƵŶŝƚ;ϲͿǇŽƵƐŚŽƵůĚďĞĂďůĞƚŽƌĞĐŽŐŶŝǌĞ͗ϭ͘ĂŐŶĞƚŝĐƉƌŽƐƉĞĐƚŝŶŐ͘

Ϯ͘ŚĞƵƐĞŽĨŵĂŐŶĞƚŽŵĞƚĞƌƐ͘

ϯ͘ŽŶĐĞƉƚŽĨŵĂƌŝŶĞŵĂŐŶĞƚŽŵĞƚĞƌƐ͘

ϰ͘ŚĞƵƐĞŽĨŵĂŐŶĞƚŽŵĞƚĞƌƐ͘

ϱ͘ƉƉůŝĐĂƚŝŽŶŽĨŵĂƌŝŶĞŵĂŐŶĞƚŽŵĞƚĞƌƐ͘

ϰϰϰ͗Ŷŝƚϲ;ĂƌŝŶĞĂŐŶĞƚŽŵĞƚĞƌƐͿ

ŚĞĞĂƌƚŚ͛ƐŵĂŐŶĞƚŝĐĨŝĞůĚŝƐƐŝŵŝůĂƌƚŽƚŚĂƚƉƌŽĚƵĐĞĚďǇĂƐŝŵƉůĞ

ďĂƌŵĂŐŶĞƚƉůĂĐĞĚŝŶƚŚĞĐĞŶƚĞƌŽĨƚŚĞĞĂƌƚŚ͘ŚĞŵĂŐŶĞƚŝĐůŝŶĞƐ

ŐĞƚŝŶƚŽƚŚĞĞĂƌƚŚĨƌŽŵƚŚĞŶŽƌƚŚƉŽůĞ͕ĂŶĚŐĞƚŽƵƚŽĨŝƚĨƌŽŵ

ƚŚĞ

ƐŽƵƚŚƉŽůĞ͘ŚƵƐƚŚĞƉŽƐŝƚŝǀĞĞŶĚŽĨƚŚĞďĂƌŵĂŐŶĞƚƉŽŝŶƚƐƚŽƚŚĞ

ƐŽƵƚŚ͕ĂŶĚǀŝĐĞǀĞƌƐĂ͘

ϰϰϰ͗Ŷŝƚϲ;ĂƌŝŶĞĂŐŶĞƚŽŵĞƚĞƌƐͿ

ĂŐŶĞƚŽŵĞƚĞƌƐŵĞĂƐƵƌĞŵŝŶŽƌĚŝĨĨĞƌĞŶĐĞƐŝŶƚŚĞƐƚƌĞŶŐƚŚŽĨ

ƚŚĞĂƌƚŚΖƐŵĂŐŶĞƚŝĐĨŝĞůĚ͘

ŽƐƚƐĞĚŝŵĞŶƚĂƌǇƌŽĐŬƐĂƌĞŶĞĂƌůǇŶŽŶͲŵĂŐŶĞƚŝĐ;ĂůƚŚŽƵŐŚ

ƐŽŵĞƐĞĚŝŵĞŶƚĂƌǇƌŽĐŬƐƐƵĐŚĂƐƐĂŶĚƐƚŽŶĞƐĐĂŶŚĂǀĞůŽĐĂů

ĐŽŶĐĞŶƚƌĂƚŝŽŶƐŽĨŵĂŐŶĞƚŝĐŵŝŶĞƌĂůƐƐƵĐŚĂƐŵĂŐŶĞƚŝƚĞͿ͘

ŐŶĞŽƵƐƌŽĐŬƐŐĞŶĞƌĂůůǇŚĂǀĞĂƐƚƌŽŶŐĞƌŵĂŐŶĞƚŝĐĞĨĨĞĐƚ͘

ĞĐĂƵƐĞŽĨƚŚĞƐĞĚŝĨĨĞƌĞŶƚĞĨĨĞĐƚƐŽŶƚŚĞŵĂŐŶĞƚŝĐĨŝĞůĚ͕

ŵĞĂƐƵƌĞŵĞŶƚƐĐĂŶďĞŵĂĚĞƚŽǁŽƌŬŽƵƚƚŚĞǀĞƌƚŝĐĂůƚŚŝĐŬŶĞƐƐĞƐ

ĂŶĚůĂƚĞƌĂůĚŝƐƚƌŝďƵƚŝŽŶŽĨƌŽĐŬƵŶŝƚƐ͘ŶƚƌŽĚƵĐƚŝŽŶ͗

ϰϰϰ͗Ŷŝƚϲ;ĂƌŝŶĞĂŐŶĞƚŽŵĞƚĞƌƐͿ

ŶŐĞŶĞƌĂů͕ƌŽĐŬƐĐŽŶƚĂŝŶŝŶŐŵĂŐŶĞƚŝĐŵŝŶĞƌĂůƐƐƵĐŚĂƐ

ŵĂŐŶĞƚŝƚĞŚĂǀĞŐƌĞĂƚĞƌŵĂŐŶĞƚŝĐƐƵƐĐĞƉƚŝďŝůŝƚǇĂŶĚƚŚĞƌĞĨŽƌĞ

ƉƌŽĚƵĐĞŵŽƌĞŝŶƚĞŶƐĞŵĂŐŶĞƚŝĐƌĞĂĚŝŶŐƐ͘

ĂũŽƌŽƌĞĚĞƉŽƐŝƚƐ;ĞƐƉĞĐŝĂůůǇŝƌŽŶͲďĞĂƌŝŶŐƵŶŝƚƐͿŚĂǀĞďĞĞŶ

ĚŝƐĐŽǀĞƌĞĚǁŝƚŚŵĂŐŶĞƚŽŵĞƚĞƌƐ͘

ŵĂƐƐŽĨŝƌŽŶůŽĐĂůůǇŝŶƚĞŶƐŝĨŝĞƐƚŚĞĞĂƌƚŚ͛ƐŶĂƚƵƌĂůŵĂŐŶĞƚŝĐ

ĨŝĞůĚ͘ĂŐŶĞƚŽŵĞƚĞƌƐ͕ŝŶƐƚĂůůĞĚŝŶĂŝƌƉůĂŶĞƐĂŶĚďŽĂƚƐ͕ĂƌĞ

ƌŽƵƚŝŶĞůǇƵƐĞĚŝŶŐĞŽƉŚǇƐŝĐĂůƐƵƌǀĞǇƐ͘

ŚĞůŽĐĂƚŝŽŶŽĨůĂƌŐĞŝƌŽŶͲƌŝĐŚŽďũĞĐƚƐ͕ƐƵĐŚĂƐƐƵŶŬĞŶƐŚŝƉƐ͕ĐĂŶ

ďĞĂĐĐŽŵƉůŝƐŚĞĚƵƐŝŶŐŵĂŐŶĞƚŽŵĞƚĞƌƐ͘ŶƚƌŽĚƵĐƚŝŽŶ͗

ϰϰϰ͗Ŷŝƚϲ;ĂƌŝŶĞĂŐŶĞƚŽŵĞƚĞƌƐͿ

ŵĂŐŶĞƚŽŵĞƚĞƌŝƐĂŶŝŶƐƚƌƵŵĞŶƚǁŚŝĐŚŵĞĂƐƵƌĞƐƚŚĞ

ŝŶƚĞŶƐŝƚǇŽĨĂŵĂŐŶĞƚŝĐĨŝĞůĚ͘ŚĞŝƌĂƉƉůŝĐĂƚŝŽŶŝŶ

ŐĞŽƉŚǇƐŝĐĂůƉƌŽƐƉĞĐƚŝŽŶŝƐĨŽƵŶĚĞĚŽŶƚŚĞƉƌŝŶĐŝƉůĞ

ƚŚĂƚƚŚĞǇĐĂŶŵĞĂƐƵƌĞĂŶĚƌĞĐŽƌĚĚĞǀŝĂƚŝŽŶƐŝŶƚŚĞ

ĂƌƚŚ͛ƐĂŵďŝĞŶƚŵĂŐŶĞƚŝĐĨŝĞůĚďƌŽƵŐŚƚĂďŽƵƚďǇƚŚĞ

ƉƌĞƐĞŶĐĞŽĨĨĞƌƌŽŵĂŐŶĞƚŝĐŵĂƚĞƌŝĂů͘ĂƌŝŶĞĂŐŶĞƚŽŵĞƚĞƌƐ͗

ϰϰϰ͗Ŷŝƚϲ;ĂƌŝŶĞĂŐŶĞƚŽŵĞƚĞƌƐͿ

ĞƚĞĐƚƐŵĂůůĞƌƚĂƌŐĞƚƐĨĂƌƚŚĞƌĂǁĂǇ͘

ĞĨŝŶĞƐŵĂůůĞƌƚĂƌŐĞƚƐĂƚŚŝŐŚĞƌƐƵƌǀĞǇƐƉĞĞĚƐ͘

ƵƌǀĞǇŝŶĂƌĞĂƐǁŝƚŚůĂƌŐĞƐƚĞĞůĂŶŽŵĂůŝĞƐĂŶĚ

ƉĞƌĨŽƌŵŝŶƐƚƌƵŵĞŶƚĐŚĞĐŬƐŽŶĚĞĐŬƉƌŝŽƌƚŽƐƵƌǀĞǇ͘

ĞƚƚĞƌĂďůĞƚŽĚĞĨŝŶĞůĂƌŐĞĂŶŽŵĂůŝĞƐ͘

ǆĐĞůůĞŶƚƉĞƌĨŽƌŵĂŶĐĞĨŽƌĂůůĂƉƉůŝĐĂƚŝŽŶƐ͕ĨƌŽŵƐŵĂůůŽďũĞĐƚĚĞƚĞĐƚŝŽŶƚŽůĂƌŐĞŐĞŽůŽŐŝĐƐƵƌǀĞǇƐ͘

ĂŐŶĞƚŽŵĞƚĞƌĚĂƚĂĐĂŶďĞƵƐĞĚƚŽŵĂƉďƵƌŝĞĚĐŚĂŶŶĞůƐ͘

ĞůĂƚŝǀĞƐŝŵƉůĞĂŶĚĐŚĞĂƉŵĞƚŚŽĚ͘ĂƌŝŶĞĂŐŶĞƚŽŵĞƚĞƌƐ͗

ϰϰϰ͗Ŷŝƚϲ;ĂƌŝŶĞĂŐŶĞƚŽŵĞƚĞƌƐͿ

ǆƉůŽƌĞƌƐĚĞĂůŽƌ͗ŶƐŚŽƌĞ͕ƐŚĂůůŽǁǁĂƚĞƌǁŽƌŬ͘

ĨĨƐŚŽƌĞƚŽǁĞĚďĞŚŝŶĚƐŝĚĞƐĐĂŶƐ͕ƐĂŶĚ

Ɛ͘

ŶƐŚŽƌĞŐĞŽƉŚǇƐŝĐĂůƐƵƌǀĞǇ͘

ƌĐŚĞŽůŽŐǇ͘

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