---
title: "Field identification criteria of fault"
subject: "Engineering Geology I"
chapter: 5
key: "semester_3/engineering_geology_i:field-identification-criteria-of-fault"
source: https://www.bctengineer.com/q/semester_3/engineering_geology_i/field-identification-criteria-of-fault
site: BCT Engineering
---

# Field identification criteria of fault

Engineering Geology I · Chapter 5: Structural Geology

- Asked in: 2081 Baisakh (new course), 2 marks; 2081 Bhadra, 3 marks; 2080 Baisakh, 2 marks; 2078 Bhadra, 4 marks; 2076 Asoj, 4 marks; 2073 Shrawan, 2 marks; 2081 Chaitra (new course), 2 marks (asked 7 times)
- Video: [Criteria for Recognition in Field - Structural Geology and Stratigraphy - Engineering Geology](https://www.youtube.com/watch?v=MHa4lh1Eifo) — Ekeeda
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_3/engineering_geology_i/field-identification-criteria-of-fault
- Whole chapter: https://www.bctengineer.com/md/semester_3/engineering_geology_i/chapter-5

## Question

What are the field identification criteria (evidences) of fault?

## Short answer

Direct evidence includes offset beds, slickensides, fault breccia and drag folds. Physiographic signs are fault scarps, linear valleys, offset streams and lines of springs. Several features together confirm a fault.

## Answer

A **fault** is a fracture in the rock mass along which the two blocks have moved relative to each other, parallel to the fracture surface. The displacement may be a few millimetres to hundreds of kilometres.

#### Evidences for recognition in the field
**Direct evidences**
- Displacement or offset of beds, dykes, veins, streams, roads or ridges.
- Repetition or omission (missing) of beds in a sequence.
- Slickensides (polished, grooved surfaces) and striations on the fault plane showing the direction of movement.
- Fault breccia, fault gouge or mylonite along the fault zone.
- Drag folds (bending of beds near the fault plane).

**Physiographic (topographic) evidences**
- Fault scarps (straight steep cliffs) and triangular facets.
- Linear valleys, straight stream courses and sudden changes in stream direction.
- Offset or beheaded streams, waterfalls and rapids along a straight line.
- Line of springs and seepages, and a sharp line of vegetation change.
- Alignment of sag ponds, lakes and hot springs.
- Abrupt change of rock type across a straight line, and earthquake epicentres in a line.

#### Note
No single evidence is final; the presence of several (such as slickensides, breccia and offset beds together) is used to confirm a fault.

## Check yourself

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

1. Which is direct evidence of a fault?
   A. Slickensides and offset or missing beds
   B. Opposite dips with symmetry
   C. Vesicles
   D. Cross bedding
   Answer: A. Shows movement. (Key point: Direct evidence)

2. Which rocks occur along fault zones?
   A. Conglomerate
   B. Breccia, gouge, mylonite
   C. Pumice
   D. Marble
   Answer: B. Crushed material. (Key point: Fault rock)

3. Which is a physiographic evidence?
   A. Ripple marks
   B. Graded bedding
   C. Fault scarp and linear valley
   D. Cleavage
   Answer: C. Straight steep cliffs. (Key point: Topographic)

4. How is a fault confirmed?
   A. Any single evidence
   B. Only a scarp
   C. Only spring
   D. Several evidences together
   Answer: D. No single evidence is final. (Key point: Confirmation)

## Related in Engineering Geology I

- [Field identification criteria of fault and fold](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afield-identification-criteria-of-fault-and) — Engineering Geology I, chapter 5, asked 2×
- [Dip amount, strike; fold identification criteria](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Adip-amount-strike-fold-identification) — Engineering Geology I, chapter 5
- [Fault classification, evidences, documentation](https://www.bctengineer.com/question.md?key=semester_3%2Fengineering_geology_i%3Afault-classification-evidences-documentation) — Engineering Geology I, chapter 5

## Related in other subjects

- [Field identification of fine-grained soils](https://www.bctengineer.com/question.md?key=semester_4%2Fsoil_mechanics%3Afield-identification-clay-silt) — Soil Mechanics, chapter 3, asked 4×