Geophysics: Overview

Introduction to Geophysics Ali O. Oncel [email_address] Department of Earth Sciences KFUPM Lecture 1 Overview Introduction to Seismology-KFUPM

Dr. Ali O. Oncel: Building 26, Room:319 (oncel@kfupm.edu.sa) Saturday : 8:00-9:00 PM room 319 Monday : 8:00-9:00 PM room 319 Wednesday : 8:00-9:00 PM room 319 Any time you can ask me an appointment through e-mail. Scheduled Office Hours Introduction to Seismology-KFUPM

Parasnis, P principles of Applied Geophysics 5E , 1997 R.J. Lillie , Whole Earth Geophysics , Prentice Hall, 1999. Recommended Text and Grading Introduction to Seismology-KFUPM GEOP 204: % Final Exam 35 Comprehensive Exam 30 Quiz 15 Homework 15 Class Participation on time 5 Monday is day for weekly exam. Wednesday is day for field-trip or work.

Homework is due one week after it is assigned
Late homework will not be accepted one week after the deadline.
Late homework will be penalized:
Homework Introduction to Seismology-KFUPM 80% for 1 day late 60% for 2 day late 40% for 3 day late 20 % for 4 day late 10% for 5 day late.

Scope of Course
Providing knowledge more about the mathematical and physical aspects of Applied and 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 Applied and Solid Earth Geophysics ………………...
Introduction to Seismology-KFUPM

Geology + Physics Geophysics Geophysics aims to interpret the subsurface by combining observations of the Earth Materials (geology) with observations of physical phenomena (physics). Introduction to Seismology-KFUPM

Forward Modeling (1) what the cause of our observations? By adjusting the model parameters, we try to find the best model that fit the predictions with observations. Introduction to Seismology-KFUPM

Applied Seismology Refraction Reflection Seismic refraction • Used to study large scale crustal layering: thickness and velocity Seismic reflection • “ Imaging” of subsurface reflectors • Difficult to determine accurate velocities and depths Introduction to Seismology-KFUPM

Inversion (2) Introduction to Seismology-KFUPM

Interpretations As for the interpretations of geophysical data, I just want emphasize that most interpretations are actually “ non-unique”. That means more than one interpretation can explain the data. The problem is like that of the “blind men and the elephant;” Thus, all the available information must be synthesized in order to obtain a better picture of the subsurface structure. It is wise to use the words like “uncertain, possibly, unclear suggestions…” when you describe your interpretations. However in the real literature, you may see that a lot of authors still use the words like “ certain, undoubtedly, positive proof, strongly suggested …” Introduction to Seismology-KFUPM

Seismic refraction profile recorded in ocean basin, Sheriff and Geldart, 1995 S – Reflections from bottom of water Refraction Interpretation D D - Direct Arrival P P - Lower Crustal Refraction within the crust and from the Moho S Introduction to Seismology-KFUPM

Fowler, 1990 Seismic Refraction Interpretation Introduction to Seismology-KFUPM

Reflection Interpretation Bowen and White, 1986 A migrated seismic-reflection profile across the Vema Transform Fault on the Mid-Atlantic Ridge at 6°N, approximately midway between the African and South American plates. Introduction to Seismology-KFUPM

Geophysics: Overview

by Prof. Dr. Ali Osman Öncel

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