---
title: "Fault versus thrust"
subject: "Engineering Geology I"
chapter: 5
key: "semester_3/engineering_geology_i:fault-versus-thrust"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/fault-versus-thrust
site: BCT Engineering
---

# Fault versus thrust

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2072 Chaitra, 2 marks
- Video: [Overview of Geologic Structures Part 2: Faults and Folds](https://www.youtube.com/watch?v=aodnQWXYkZ0) — Professor Dave Explains
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/fault-versus-thrust
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

How do you differentiate fault and thrust?

## Short answer

A thrust is a low-angle reverse fault (dip < 45°) where the hanging wall moves up over the footwall under compression, pushing older rocks over younger. A fault is any fracture with displacement, regardless of dip or stress type.

## Answer

| Point | Fault | Thrust |
|---|---|---|
| Meaning | Fracture with relative displacement of rock blocks, any type | A special type of low-angle reverse fault |
| Dip of plane | Any (low to vertical) | Low angle, less than 45° |
| Movement | Normal, reverse, strike-slip or oblique | Hanging wall moves up and over the foot wall |
| Stress | Tension, compression or shear | Compression |
| Result | Younger/older rocks may be juxtaposed | Older rocks pushed over younger rocks |
| Example | Normal fault in graben | Main Central Thrust, Main Boundary Thrust of Nepal |

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. What is a thrust?
   A. A vertical normal fault
   B. A fracture with no displacement
   C. A bend of rock beds
   D. A low-angle reverse fault
   Answer: D. Thrust is a special type of low-angle reverse fault. (Key point: Definition of thrust)

2. What is the dip of a thrust plane?
   A. Less than 45 degrees
   B. More than 45 degrees, up to vertical
   C. Exactly vertical
   D. Exactly 90 degrees
   Answer: A. A thrust has a low angle, less than 45 degrees. (Key point: Dip of thrust)

3. Which statement is correct about thrusts?
   A. They form by tension and drop the hanging wall
   B. They form by compression and push older rocks over younger rocks
   C. They form by shear with horizontal motion only
   D. They put younger rocks over older rocks
   Answer: B. Thrust movement is compressional: hanging wall moves up and over, putting older rocks over younger. (Key point: Stress and result)

## Related in Engineering Geology I

- [Fold, fault, joint, thrust in tunnelling](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afold-fault-joint-thrust-in) — Engineering Geology I, chapter 5
- [Fault versus joint](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afault-versus-joint) — Engineering Geology I, chapter 5, asked 2×
- [Fault gouge, breccia and mylonite](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afault-gouge-breccia-and-mylonite) — Engineering Geology I, chapter 5
- [Genetic classification of fault and joint](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Agenetic-classification-of-fault-and) — Engineering Geology I, chapter 5
- [Silicate versus carbonate minerals in the field](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Asilicate-versus-carbonate-minerals-in) — Engineering Geology I, chapter 3, asked 2×

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