Date & Magnitude

A powerful 7.7 magnitude earthquake struck central Myanmar on March 28, 2025 near Mandalay followed by a 6.4 magnitude aftershock within 11 minutes.

Epicentre

~20 km from Mandalay near Sagaing Fault one of Southeast Asia most active strike-slip faults.

Seismic Impact

Over 3,000 deaths widespread destruction of homes, religious sites & bridges. USGS estimates potential fatalities could exceed 10,000.

Geographical Reach

Tremors felt as far as Bangkok (~1,000 km away). In Bangkok 33-storey under-construction building collapsed; seismic waves also triggered swimming pool oscillations (seiches) on rooftops.

Seismic Seiches

Oscillations in rooftop pools in Bangkok occurred due to long-period seismic waves despite city distance from epicentre.

Amplified Damage Zones

Southern areas of Sagaing fault built on Irrawaddy river alluvium suffered more due to amplified seismic waves.

Escape of Damage

China Yunnan Province & eastern India escaped major destruction due to energy dispersion direction (north-south).

Fault Mechanics

Sagaing Fault is a strike-slip fault accommodating 50–55% of plate motion in region with a slip rate of 15–25 mm/year. It allows horizontal movement unlike thrust faults.

Plate Tectonics

Caused by oblique convergence between India & Eurasia Plates. A microplate (Burma Sliver) lies between Sagaing fault & Indian plate.

Tectonic Context

Southeast Asia hosts multiple tectonic features Himalayas, Shillong Plateau, Indo-Burman Range & Andaman-Nicobar subduction zone making it highly earthquake-prone.

Historical Earthquakes

Similar events 1839 Ava earthquake (Mag. 7.8), 1946 quake north of Mandalay (Mag. 7.7) & 2016 Bagan earthquake.

Past Megaquakes

The region also saw a 2004 earthquake (Mag. 9.2) & tsunami originating from Indo-Burmese subduction zone.

Depth Factor

The 10 km shallow depth of quake increased its devastating impact. Shallow quakes are typically more destructive.

Transform Fault Type

The Sagaing Fault is a ridge-trench transform fault system that extends ~1,400 km linking Andaman spreading centre in south to eastern Himalayas.

Future Risk

A significant portion of fault remains unruptured suggesting that more earthquakes are expected.

Warning for India

Given India own seismic vulnerability experts urge scientific earthquake mitigation strategies particularly for urban infrastructure.

Civil War Complication

Myanmar earthquake response is hindered by its ongoing civil war limiting relief & reconstruction efforts.

Zone V

0.36g

IX or above (Very Severe)

Very High Risk

Collision of Indian & Eurasian plates (Himalayan belt)
Active thrust faults & crustal deformation

Entire Northeast India
Jammu & Kashmir, Uttarakhand
Bihar (Northern part)
Andaman & Nicobar Islands

Zone IV

0.24g

VIII (Severe)

High Risk

Proximity to Himalayan foothills & Delhi ridge
Fracture zones in peninsular India
Fault systems in Indo-Gangetic basin

Delhi-NCR
Parts of Haryana, Punjab
Sikkim, Himachal Pradesh
Western Uttar Pradesh, Gujarat (Kutch region)

Zone III

0.16g

VII (Moderate to Strong)

Moderate Risk

Ancient faults & rift systems
Seismic activity along Narmada & Son lineaments
Peninsular shear zones

Mumbai, Kolkata, Chennai
Parts of Kerala, Goa
Odisha, Andhra Pradesh
Southern Rajasthan, Madhya Pradesh

Zone II

0.10g

VI or less (Low)

Low Risk

Stable continental region
Intraplate earthquakes can still occur
Remote chance of moderate earthquakes

Bangalore, Hyderabad
Central Karnataka
Most of Tamil Nadu
Chhattisgarh, Telangana

Fault Type

Right-lateral (dextral) strike-slip fault (horizontal displacement).

Fault Geometry

Nearly vertical fault plane; segmented structure with several branches including Meiktila, Yamethin & Tagaung segments.

Length

Approx. 1,400 km stretching from Andaman Sea spreading center to Eastern Himalayan syntaxis.

Crustal Thickness Variation

Varies along its length thinner crust near Andaman Sea (~20–25 km), thicker near Himalayas (~35–40 km).

Associated Geological Structures

Flanked by Central Myanmar Basin on west & Shan Plateau on east. Associated with features like Shweli & Namwan Faults.

Microplate Involvement

The Sagaing Fault delineates boundary of Burma (or Burma-Sunda) microplate, which is being sheared between Indian & Sunda plates.

Deformation Style

Accommodates strike-slip displacement & transpressional uplift in northern segments near Eastern Himalayas.

Seismic Gap Zones

Identified in Bago–Taungoo & Shwebo–Sagaing segments; considered high-risk zones due to absence of large earthquakes in recent history.

Seismic Reflection/Imaging Studies

Seismic tomography indicates velocity anomalies (low-velocity zones) beneath fault suggesting fluid presence & crustal weakness.

Paleoseismic Evidence

Trenching studies (esp. in Meiktila) indicate recurrence intervals of large earthquakes ~150–200 years.

GPS Monitoring Stations

Deployed across Myanmar to track fault slip, crustal shortening & post-seismic deformation. Notably part of GEODASIA network.

Geothermal Activity

Presence of hot springs & shallow geothermal gradients along fault-parallel zones suggest ongoing crustal stress & strain accumulation.

Landslide & Surface Rupture Risks

High; particularly in northern regions where fault crosses mountainous terrain. Surface ruptures up to 2 meters recorded in earlier events.

Volcanic Interaction

Proximity to Popa Volcano & Mt. Taungtha shows interaction between tectonics & volcanism in central arc segment.

Hazard Zonation

Myanmar Earthquake Committee classifies several cities like Sagaing, Mandalay, Taungoo under very high risk seismic zones.

Tectonic Evolution

The fault has evolved since Late Miocene (~10 million years ago) during oblique convergence between India & Sunda plates.

Comparison with Other Faults

Comparable in scale & seismicity to San Andreas Fault (California) & North Anatolian Fault (Turkey) all right-lateral strike-slip systems.

PRACTICE QUESTION

Q. Which of following statements about Sagaing Fault & recent 2025 Mandalay earthquake are correct?

1. Sagaing Fault is a typical strike slip fault located between Indo-Burman Range & Central Myanmar Lowlands.
2. 2025 Mandalay earthquake originated at a shallow depth of about 10 km contributing to its widespread impact.
3. The earthquake energy from Sagaing fault typically disperses east-west affecting northeastern India most.
4. The Sagaing fault accommodates more than 50% of tectonic motion between India & Eurasia plates in region.

Select correct answer using code below:

A. 1, 2 & 4 only
B. 1 & 3 only
C. 2 & 4 only
D. 1, 2, 3 & 4

Correct Answer: (A)

Explanation:

Statement 1 is Correct: Sagaing Fault is indeed north-south running strike-slip fault marking tectonic boundary between Indo-Burman Range & Central Myanmar Lowlands.

Statement 2 is Correct: 2025 Mandalay earthquake originated at a shallow depth (~10 km) increasing its destructive capacity & expanding felt area.

Statement 3 is Incorrect: The seismic energy disperses north-south not east-west which is why eastern India escaped major damage.

Statement 4 is Correct: The fault is responsible for 50–55% of total plate motion in this region due to oblique convergence & strain partitioning.