Solid-Earth Geophysics: Overview
-
Upload
ali-osman-oencel -
Category
Business
-
view
1.433 -
download
2
Transcript of Solid-Earth Geophysics: Overview
Solid Earth Geophysics-Geop503
Ali [email protected].
saDepartment of Earth Sciences, KFUPM
Introduction to Solid-Earth Geophysics
Dr. Ali O. Oncel : Building 26, Room:319
Saturday. 14.00-16:00 PM room 319
Monday. 14:00-16:00 PM room 319
Any time you get appointment by e-mail or you can come to see me based on open-door policy.
Scheduled Office Hours
Solid Earth Geophysics?
Understanding the Earth’s composition and dynamics, and their relationships with the surface geological phenomena, using the means of physics.
Analogy: How do you figure out what is going on inside an apple, egg, golf ball, human body, without slicing it open?
Suggestions: you can weigh it, spin it, heat it, probe it with electromagnetism, etc. You can also look at what is naturally emitted from it.
What is the purpose of Solid-Earth Geophysics?
Scope of Course
Providing knowledge more about the mathematical and physical aspects of solid Earth geophysics such as the currently accepted physical models used to describe the Earth's interior and evolution.
Providing knowledge about the most important datasets and methods which have been used to learn about Solid Earth Geophysics.
Providing knowledge of how these datasets and application of the scientific method by many scientists, have been used to perform current models for the physical characteristics of the Earth, its chemical composition, and the past and ongoing processes modifying the Earth.
Providing knowledge of the many exciting problems that still remain for research to be solved.
What is the scope of studies on Solid-Earth Geophysics?
Earth FormationEarth Formation
What is the past knowledge on Earth’s Interior?
http://www.seismosoc.org/about/memb_info.html
Complete Archive of Complete Archive of BSSABSSA Back Issues from 1911-2006 Back Issues from 1911-2006
Earth FormationThe knowledge on Earth’s Interior in 1924
From what you can see, inner core has not been known, where Lehman, who is Danish Seismologist and died in 1993 aged 104, discovered the inner core in 1936.
James and Majelwane, 1924
MOHOMOHO
Core-mantle Core-mantle boundaryboundary
How do we know?
*Crustal thicknesses are depicted out of scale for clarity.
Upper mantle evidence comes from mantle rocks thrust onto continents (e.g., ophiolites); xenoliths; lab experiments• Lower mantle completely based on experiments
upper mantle “Peridotite”:
65% olivine: (Mg,Fe)2SiO4
25% orthopyroxene (Mg,Fe)2Si2O6
10% clinopyroxene (Ca,Mg,Fe)2Si2O6
+ garnet (Mg,Fe)3AL2Si3O12
phase changes through transition zonelower mantle
85% Perovskite: (Mg0.9Fe0.1)SiO3
15% magnesiowustite (Mg0.9Fe0.1)O
+ Ca Perovskite ( Ca, Mg, Fe )SiO3
+ Corundum Al2O3outer core
90% Fe +Ni alloy
10% lighter alloy (FeO, S, Si, ?)
inner core
solid Fe + ?
continental crust*oceanic crust*
http://www.geo.cornell.edu/geology/classes/geol388/syl_04.html
Internal structure by Drilling Program
http://www.icdp-online.de/contenido/icdp/front_content.php
The deepest drill hole is about 12 km deep, which doesn't even make it past the bottom of the crust. Certain volcanic eruptions can bring up material from deeper, but still less than 1000 km deep.
How do we know by Global Drilling Program?
Internal structure by Seismology
Seismology: When earthquakes happen, the ground shakes and seismic waves travel outward from the earthquake. If the earthquake is big enough, then the seismic waves can be detected on the other side of the earth. The speed of seismic waves is related to the properties of the material they travel through, and we can try to extract information on the properties of the Earth.
How do we know by Seismology?
What are the main characteristics of Body waves?
P (primary or push) waves comparable to sound waves alternating dilatations and
compressions transmitted through liquid or solid
may be heard when they emerge at surface
S (secondary or shear) waves slower traveling shears rock sideways perpendicular to
direction of propagation not transmitted through liquid
Some typical velocities (granite)P=4.8km/s S=3.0km /s
Body Waves and Internal structure
Travel just below or along the ground’s surface
Surface Waves and Internal structure
Especially damaging to buildings
Slower than body waves; rolling and side-to-side movement
What are the main characteristics of Rayleigh waves?
Rayleigh Waves
Travel confined to near surface Wave displacements fall off rapidly with
depth Love waves
sideways motion perpendicular to travel motion like an S wave with no vertical
component Rayleigh waves
rolling motion involving vertical & horizontal displacements in direction of travel
Surface waves travel more slowly than body waves
Love waves travel faster than Rayleigh waves and therefore arrive earlier
Surface Waves and Internal Structure?
Love Waves
What are the main characteristics of Love waves?
Assignment, Due to MondayPlease also submit your short CV to Class Page. Just Click “Comments” on Front Page for submission. Mention about yourself, and your expectation with the class.