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

# Fault versus joint

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2081 Kartik (new course), 2 marks; 2068 Baisakh, 2 marks (asked 2 times)
- Video: [Faults & Joints](https://www.youtube.com/watch?v=UIvosdkZBdQ) — Miran Fattah
- 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-joint
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

Differentiate between fault and joint.

## Short answer

A fault shows displacement along the fracture, producing breccia, gouge, and slickensides; a joint lacks significant movement. Faults offset beds and cause earthquakes; joints reduce rock strength and control seepage without large displacement.

## Answer

| Point | Fault | Joint |
|---|---|---|
| Movement | Displacement of the two sides along the fracture | No displacement, or negligible |
| Size | Long, from metres to hundreds of kilometres | Short, usually in centimetres to metres |
| Associated features | Breccia, gouge, slickensides, drag folds | Usually clean surfaces; sometimes mineral filling |
| Occurrence | Single plane or zone | In sets and systems, regularly spaced |
| Cause | Tectonic stress above rock strength, with relative movement | Tension, cooling, unloading or compression without movement |
| Effect | Offsets beds, causes earthquakes | Provides weak planes and ground water paths |
| Engineering effect | Major weak zone, large leakage, seismic hazard | Reduces strength, causes seepage and slope failure |

## Check yourself

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

1. What is the basic difference between a fault and a joint?
   A. A joint has large displacement, a fault has none
   B. A fault occurs only in igneous rock
   C. A fault has displacement of the two sides along the fracture, a joint has none or negligible
   D. A joint is always much longer than a fault
   Answer: C. Displacement along the fracture separates a fault from a joint. (Key point: Main difference)

2. Which features are typical of a fault but not of a joint?
   A. Breccia, gouge, slickensides and drag folds
   B. Regularly spaced sets with clean surfaces
   C. Cooling cracks and mineral filling only
   D. Parallel columnar blocks
   Answer: A. Fault movement crushes and polishes rock giving breccia, gouge, slickensides and drag folds; joints usually have clean surfaces. (Key point: Associated features)

3. How do joints usually occur?
   A. As a single long plane or zone
   B. In regularly spaced sets and systems
   C. Only along plate boundaries
   D. Only as offset beds
   Answer: B. Joints occur in sets, while a fault is a single plane or zone. (Key point: Occurrence)

4. Which is a major engineering effect of faults but not typically of joints?
   A. Providing small seepage paths only
   B. Making quarrying easier
   C. Being only a minor surface crack
   D. Seismic hazard and a major weak zone with large leakage
   Answer: D. Active faults can cause earthquakes and large weak zones; joints mainly reduce strength and give seepage paths. (Key point: Engineering effect)

## Related in Engineering Geology I

- [Engineering significance of joint and fault](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Aengineering-significance-of-joint-and) — Engineering Geology I, chapter 5, asked 2×
- [What is joint; engineering significance of joint and fault](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Awhat-is-joint-engineering-significance) — Engineering Geology I, chapter 5, asked 2×
- [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
- [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
- [Fold, fault and joint; attitude](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afold-fault-and-joint-attitude) — Engineering Geology I, chapter 5
- [Fault versus thrust](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afault-versus-thrust) — Engineering Geology I, chapter 5

## Related in other subjects

- [Bilateral, multilateral, joint venture; external environment](https://www.bctengineer.com/question.md?key=semester_7%2Fproject_engineering%3Abilateral-multilateral-joint-venture-env) — Project Engineering, chapter 1, asked 2×