The Indo-Burman Arc represents a critical and complex convergent plate boundary that serves as a geological bridge linking the Himalayan collision zone with the Sunda subduction system in Southeast Asia. This arc is characterized by the oblique northeastward movement of the Indian Plate relative to the Eurasian Plate, creating one of the widest and most seismically active deformation zones in the region. Stretching from the Bay of Bengal across Myanmar to the Shan Plateau, this zone exhibits diverse tectonic behaviors that have significant implications for earthquake and tsunami hazards affecting millions of people in Myanmar, Northeast India, Bangladesh, and neighboring countries. A comprehensive understanding of the arc’s tectonic framework, seismic history, and active processes is essential for effective disaster preparedness and risk mitigation in this densely populated and geologically dynamic region.

Geological Framework of the Indo-Burman Arc

Plate Kinematics and the Burma Platelet

The Indian Plate advances northeastward at rates ranging from approximately 3.5 to 5 centimeters per year, converging obliquely with the Eurasian Plate. This convergence does not occur along a single fault but is distributed across a broad deformation zone that includes subduction, strike-slip faulting, and crustal shortening. A key feature of this region is the Burma Platelet, a crustal sliver that accommodates the along-strike component of the Indian Plate’s motion via strike-slip faulting.

The main subduction interface beneath the Indo-Burman Ranges dips gently eastward, allowing the Indian Plate to subduct beneath the Burma Platelet. Meanwhile, the strike-slip motion is primarily taken up by the Sagaing Fault, a prominent dextral strike-slip fault that runs parallel to the arc’s eastern margin. This partitioning of motion explains why the Indo-Burman Arc exhibits both megathrust earthquake potential along the subduction interface and significant strike-slip seismicity along major faults.

Geodetic studies estimate that approximately half of the total plate convergence is accommodated by the Sagaing Fault, while the remainder is absorbed by deformation within the accretionary wedge and subduction zone. This complex kinematic regime results in a distributed strain pattern and multiple seismic sources with varying rupture characteristics.

Major Structural Elements of the Arc

  • The Sagaing Fault: Stretching over 1,200 kilometers, the Sagaing Fault is one of the most active strike-slip faults globally, exhibiting slip rates of 18 to 20 millimeters per year. It poses a direct threat to major urban centers including Mandalay, Naypyidaw, and Yangon. The fault’s linear segments are capable of generating large magnitude earthquakes, often in clustered sequences.
  • The Churachandpur-Mao Fault (CMF): Located on the western flank of the Indo-Burman Ranges, this fault delineates the accretionary wedge from the Indian Plate foreland. The CMF is responsible for moderate to large thrust earthquakes, particularly affecting the Indian states of Manipur and Mizoram, where notable seismic events have been recorded.
  • The Kabaw Fault: This major east-dipping reverse fault marks the boundary between the Indo-Burman Ranges and the Central Myanmar Basin. It plays a significant role in crustal shortening and uplift, contributing to topographic relief and seismic hazard in the region.
  • Andaman Spreading Center: At the southern terminus of the arc, the Andaman Sea hosts back-arc spreading processes. The Andaman Spreading Center connects the Sagaing Fault to the Sumatran fault system across the Andaman and Nicobar Islands, complicating the regional tectonic stress regime and influencing seismicity patterns.

Seismic Behavior and Rupture History

Great Historical Earthquakes and Paleoseismic Evidence

The Indo-Burman Arc has a well-documented history of large earthquakes, with paleoseismological studies revealing multiple prehistoric and historic rupture events. The most significant known earthquake along the arc is the 1762 Arakan earthquake, estimated to have reached a magnitude between 8.5 and 9.0. This megathrust event produced a major tsunami and resulted in uplift of coastal areas by several meters, as evidenced by raised coral reef terraces and shoreline displacements along more than 500 kilometers of the western coast of Myanmar and Bangladesh.

This earthquake serves as a critical analog for the arc’s future seismic potential, demonstrating that the locked segment of the megathrust is capable of generating devastating tsunamigenic earthquakes that can affect wide coastal regions. Other paleoseismic investigations have identified multiple rupture episodes along the Sagaing Fault and the accretionary wedge, highlighting the arc’s long-term seismic activity.

Contemporary Seismicity and the Seismic Gap Phenomenon

Modern instrumental records indicate that seismicity in the Indo-Burman Arc is largely dominated by upper plate crustal earthquakes and intraslab events, with relatively fewer large megathrust ruptures documented in recent decades. Notable recent earthquakes include the 2016 Mw 6.9 Chauk earthquake and the 2012 Mw 6.8 Shwebo earthquake, both of which caused significant damage and casualties within the Burma Platelet and along the Sagaing Fault.

Despite frequent moderate earthquakes, a prominent seismic gap persists along the basal detachment beneath the Indo-Burman Ranges. Geodetic measurements from GPS networks reveal that this segment remains largely locked, accumulating strain that could be released in a future great earthquake. Models suggest that a rupture of this locked zone could result in an earthquake of magnitude 8.5 or higher, with potentially catastrophic consequences. The United States Geological Survey (USGS) and other institutions classify this region as a high seismic hazard zone, emphasizing the urgent need for preparedness and mitigation efforts.

Active Tectonic Processes Shaping the Indo-Burman Arc

Subduction Zone Dynamics

The Indian Plate’s subduction beneath the Burma Platelet occurs at a remarkably shallow angle, largely influenced by the thick sedimentary deposits of the Bengal Fan entering the trench. This thick sediment layer acts as a lubricant, reducing friction in some parts of the interface but also contributing to the formation of a broad and locked seismogenic zone capable of generating large megathrust earthquakes.

The shallow dip of the subduction interface means that the seismogenic zone extends inland beneath populated areas of the Indo-Burman Ranges. This configuration increases the risk of strong ground shaking and tsunami generation. The accretionary wedge formed by sediment accretion and faulting adds complexity to the fault geometry and acts as a site for strain accumulation and release.

Strike-Slip Fault Systems

Strike-slip faulting plays a vital role in accommodating the lateral component of plate motion within the arc. The Sagaing Fault is the most prominent of these, functioning as a continental transform fault that facilitates the northward escape of the Burma Platelet relative to the Sundaland Block. The fault consists of several structurally immature, highly linear segments that rupture in large earthquakes, sometimes in clustered sequences.

The Sagaing Fault’s high slip rate and history of significant seismic events make it a persistent hazard to densely populated regions. Its current period of relative seismic quiescence in certain segments is a cause for concern, as strain is expected to be accumulating and may be released in future earthquakes.

The Churachandpur-Mao Fault, although exhibiting a lower slip rate, also contributes to crustal shortening and seismic hazard on the western margin of the Indo-Burman Ranges. Its proximity to populated areas in Northeast India increases its importance in regional earthquake risk assessments.

Geohazards and Societal Impact

Tsunami Generation and Coastal Vulnerability

The 1762 Arakan earthquake clearly demonstrated the Indo-Burman Arc’s capability to generate destructive tsunamis. The combination of shallow subduction, a large accretionary wedge, and steep coastal bathymetry creates favorable conditions for both tectonically induced uplift-driven tsunamis and submarine landslide-triggered waves.

Coastal areas along the Bay of Bengal, including parts of Bangladesh, Myanmar, and eastern India, are densely populated and economically vital. A major tsunami originating from a megathrust rupture could reach these coastlines within minutes to an hour, posing severe threats to life and infrastructure. The Andaman and Nicobar Islands, situated east of the arc, are also vulnerable to tsunami waves generated by ruptures along the eastern margin of the arc, further highlighting the broad spatial extent of tsunami risk.

Ground Deformation, Liquefaction, and Secondary Hazards

The Central Myanmar Basin, encompassing the Irrawaddy River delta and the city of Yangon, is characterized by thick, unconsolidated sedimentary deposits. These sediments are particularly susceptible to liquefaction during strong ground shaking, which can cause severe ground failure, structural damage, and disruption of lifelines such as roads and utilities.

Earthquakes on the Sagaing Fault or the underlying megathrust could trigger widespread liquefaction in the basin, threatening critical infrastructure, including ports, industrial facilities, and residential neighborhoods. Additionally, the steep slopes of the Chin Hills and Naga Hills are prone to earthquake-induced landslides, which can block transportation routes, isolate communities, and compound the disaster response challenges.

Building Resilience: Strategies for Risk Reduction

Enhanced Seismic Monitoring and Scientific Research

Recent years have seen significant progress in seismic monitoring throughout Myanmar and Northeast India, facilitated by international collaborations. Institutions such as the Earth Observatory of Singapore and the German Research Centre for Geosciences (GFZ) have contributed to expanding seismic networks, enabling real-time earthquake detection and improving understanding of fault mechanics and strain accumulation.

Despite these advancements, seismic station coverage remains limited in remote and mountainous areas, creating gaps in the monitoring network. Additionally, public access to seismic data and detailed hazard maps remains restricted in some regions, hindering effective urban planning and preparedness. Continued investment in scientific research, data transparency, and capacity building is essential for improving earthquake early warning systems and risk communication.

Engineering Practices and Urban Planning

Myanmar has developed seismic design codes aimed at enhancing the earthquake resilience of new construction, particularly for government infrastructure. However, enforcement of these codes is inconsistent, especially in rapidly growing urban centers like Yangon and Mandalay, where many buildings have been constructed without adequate engineering oversight.

Seismic hazard assessments emphasize the urgent need for retrofitting existing vulnerable structures, especially critical facilities such as schools, hospitals, and emergency response centers. In Northeast India, code updates following the 2016 Manipur earthquake have improved structural resilience, but challenges with enforcement and resource availability persist.

Urban planning must incorporate detailed hazard zoning and land-use policies that restrict development in high-risk zones prone to liquefaction, landslides, and severe ground shaking. Integrating geological and geotechnical data into planning processes will be key to reducing future losses.

Community Preparedness and Public Awareness

Effective disaster risk reduction relies heavily on community preparedness and public awareness. In Myanmar and Northeast India, numerous public education campaigns have been undertaken to promote earthquake awareness, evacuation drills, and adoption of earthquake-resistant construction techniques.

Local non-governmental organizations and community groups play a vital role in disseminating information, especially in rural and remote areas where government outreach is limited. Nonetheless, translating awareness into actionable preparedness remains a challenge. Households and communities need to develop and regularly practice emergency plans, secure heavy objects, and retrofit homes where possible.

Preparedness strategies must consider the range of possible seismic sources in the Indo-Burman Arc, including megathrust ruptures, strike-slip fault earthquakes, and intraslab events, each producing different shaking intensities and damage patterns. Multi-hazard approaches that include tsunami evacuation planning are particularly important for coastal populations.

In summary, the Indo-Burman Arc is a region of intense tectonic activity where the collision of major plates drives frequent deformation and seismicity. The arc’s geological complexity and active fault systems pose ongoing earthquake and tsunami hazards to millions of people. Scientific evidence underscores the potential for future great earthquakes, necessitating integrated efforts in monitoring, engineering, urban planning, and community preparedness. By leveraging geological knowledge and fostering resilient societies, the Indo-Burman Arc region can better withstand the inevitable seismic events that lie ahead.