ÖNCEL AKADEMİ: INTRODUCTION TO SEISMOLOGY

Department of Earth Sciences KFUPM Introduction to Seismology Fault Mechanism Introduction to Seismology-KFUPM Ali Oncel [email_address]

Previous Lecture ,[object Object],[object Object],[object Object],[object Object],Introduction to Seismology-KFUPM

Review: Earthquake Fault Mechanism ,[object Object],[object Object],Introduction to Seismology-KFUPM

Review: Earthquake Fault Mechanism The type of faulting may be identified (reverse, normal, strike-slip) but the particular fault plane cannot be determined. So they both are shown as the possible solutions. The three stresses: two horizontal plus the vertical. Why is the significance to understand the style of faulting? Because, they are also telling us about the stresses acting within Earth. Introduction to Seismology-KFUPM

Faulting Stresses ,[object Object],[object Object],[object Object],[object Object],Smallest vertical stress - Reverse Faulting/ Compressional stresses σ max σ min Introduction to Seismology-KFUPM

Radiation Patterns ,[object Object],source receiver North The azimuth is always measured clockwise from North and varies between 0 and 360 degrees. Introduction to Seismology-KFUPM Azimuth

First Motions Introduction to Seismology-KFUPM

Example: 2004 Sumatra EQ Source: http://iisee.kenken.go.jp/staff/yagi/eq/Sumatra2004/Sumatra2004.html Introduction to Seismology-KFUPM

What types of Earthquake Software? ,[object Object],[object Object],[object Object],[object Object],Introduction to Seismology-KFUPM

What are the sources of Seismic Data? ,[object Object],[object Object],[object Object],Global Seismic Network Introduction to Seismology-KFUPM

1. visit to IRIS PAGE from http://www.iris.edu/seismon/ Introduction to Seismology-KFUPM

2. Then, click http://www.iris.edu/seismon/ Introduction to Seismology-KFUPM

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4. Now, the station list is given where data is available. Introduction to Seismology-KFUPM

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Let’s come back to discuss earthquake fault mechanism b d Introduction to Seismology-KFUPM

Cross section of reverse fault, earthquake focus and quadrants of compression and dilatation. First motions observed at the surface reveal patterns of compression and dilatation. Introduction to Seismology-KFUPM

Focal mechanism solution for a fault is commonly a lower focal sphere projection . For a dip-slip fault, this projection is equivalent to the compression/dilatation pattern viewed by a bird flying over the earthquake focus. Black = Compression White = Dilatation Introduction to Seismology-KFUPM

Cross sections of Dip-Slip Faults C= Compression D= Dilatation The focal mechanism solution for a reverse fault (a) has a compression (black) in the inside portion of the circle, surrounded by regions of dilatation (white) The opposite pattern is observed for a normal fault (b) Introduction to Seismology-KFUPM

Introduction to Seismology-KFUPM A=? B1=? B2=? C=?

Introduction to Seismology-KFUPM

ÖNCEL AKADEMİ: INTRODUCTION TO SEISMOLOGY

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ÖNCEL AKADEMİ: INTRODUCTION TO SEISMOLOGY