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

([email protected])

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

Website

Password: Geop503oncel

http://geop503kfupm.pbwiki.com/

Course Syllabus

http://geop503kfupm.pbwiki.com/CourseSyllabus

Course Book: The Solid Earth by C.M.R. Fowler-2005

Grading

http://geop503kfupm.pbwiki.com/Presentation

Schedule: Weekly Presentation

http://geop503kfupm.pbwiki.com/Geop503_Discussion_Paper

Presentation: Paper of the week 1

http://faculty.kfupm.edu.sa/ES/oncel/geop503reading.htm

Geophysics: Geology + Physics

What is Geophysics?

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

What did we know about Earth between 1920-1930?

What did we know about Earth between 1940-1950?

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

Earth Formation

Why temperature/pressure is increased with depth?

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?

Shadow Zone - no earthquake

waves

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?

Reading Assignment

http://www.solarviews.com/eng/earthint.htm

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.