IS 1893-2016: What India's Seismic Zones Actually Mean
"The plot is in Seismic Zone V" tends to be said like a verdict. It is not one. It does not mean an earthquake is coming, that you cannot build, or that your building will fall. It sets the minimum earthquake design a structure has to be built for, and that is the part worth understanding.
General information only. IS 1893 and IS 13920 are Bureau of Indian Standards documents. For any real project, use the published codes and a licensed structural engineer.
What IS 1893 is
IS 1893 is the Indian standard for earthquake resistant design of structures. Part 1, revised in 2016, covers general provisions and buildings. It divides the country into four zones, II to V. There is no Zone I: the former Zone I was merged into Zone II in the 2002 revision. Each zone has a zone factor, Z, that goes into the design calculations.
| Zone | Damage risk | Z | Broadly where |
|---|---|---|---|
| II | Low | 0.10 | Parts of peninsular and south-central India |
| III | Moderate | 0.16 | Large parts of central and southern India, including parts of Kerala, Maharashtra, Madhya Pradesh and Odisha |
| IV | High | 0.24 | Much of the Indo-Gangetic plain including Delhi NCR, Bihar and north Bengal, and parts of the Himalayan states |
| V | Very high | 0.36 | Most of Northeast India including all of Assam, the Rann of Kutch, parts of Kashmir and the western Himalaya, and the Andaman and Nicobar Islands |
The "where" column is a broad guide, not a lookup. Zone lines on the BIS map do not follow district boundaries neatly, so a plot near a line needs confirming against the code or by your engineer.
What the zone factor means
Z is not a probability. It is an engineering parameter, the ground acceleration for the maximum considered earthquake as a fraction of gravity. The design calculation uses half of it for the design basis earthquake, and then adjusts for the building's importance, its structural system, the soil and how flexible the building is.
The useful way to read the table is as a ratio. Zone V's 0.36 is 3.6 times Zone II's 0.10, so a building in Zone V is designed for far larger sideways forces than the same building in Zone II. That is why the same drawing cannot simply be moved from one zone to another.
What changes in Zone IV and V
The exact requirements depend on the building's type, height and use, and your structural engineer applies them. The direction of travel is consistent, though.
- Ductile detailing. Reinforced concrete frames are detailed to IS 13920:2016, with closer stirrups near beam-column joints, confined columns and careful joint reinforcement, so the structure can bend a long way without a sudden failure.
- Masonry. Plain load-bearing masonry is a poor fit for high zones. Where masonry is used, IS 4326 style measures such as bands and vertical reinforcement are used to hold it together.
- Ground. Where the site has loose, saturated sand or silt, liquefaction needs to be assessed. This is relevant on river plains, including the Brahmaputra valley.
- Importance. Schools, hospitals and similar buildings are designed with higher importance factors.
"There has been no earthquake here for years, so it must be low risk"
This is the most common wrong idea about zones. The zone reflects long-term tectonic stress in a region, not the last few decades of events. Great earthquakes are rare on a human timescale, so a quiet stretch tells you very little.
Northeast India shows this well. It sits where the Indian plate meets the Eurasian and Burma plates, and it has had some of the largest earthquakes recorded on the subcontinent, including Shillong in 1897 (about magnitude 8) and the Assam-Tibet earthquake of 1950 (about magnitude 8.6). A decade without a large event does not change the zone or what your building must be designed for.
IS 13920 in one paragraph
IS 13920:2016 is the code for ductile design and detailing of reinforced concrete structures subject to seismic forces. Ductility is the ability to deform a lot without breaking suddenly, which in an earthquake buys people time. It is the detailing code that goes with IS 1893: IS 1893 says what forces to design for, and IS 13920 says how to detail the beams, columns and joints so they can take them. It clearly applies in Zones IV and V, and your engineer will confirm what it requires for Zone II or III projects.
Finding the zone for a plot
The BIS map is published, but reading it for a single address is error-prone near boundaries. For a pin in India, a Geo Prithvi Report states an IS 1893 zone. We work this out from coordinate ranges that approximate the BIS map, so treat the zone as an indication, and have your engineer confirm it when the plot is close to a zone boundary. The methodology page describes how.
The report also lists the earthquakes of magnitude 3.0 and above that the USGS recorded within 100 km over the last 10 years, with distance and depth. Outside India, Geo Prithvi Report does not use IS 1893. It uses that country's own standard where it applies one and names it, and says "no national code applied" where it does not.
Check the zone and the recent earthquakes for your plot
A Geo Prithvi Report gives the zone for Indian locations and the 10-year earthquake log within 100 km.
Generate a report One-time fee from ₹299, GST invoice included. A Geo Prithvi Report is not a legal certificate or an engineering survey.Common questions
Which states are in Seismic Zone V?
Most of Northeast India, including all of Assam, falls in Zone V, along with the Rann of Kutch, parts of Kashmir and the western Himalaya, and the Andaman and Nicobar Islands. Zone lines do not follow state or district borders exactly, so confirm the zone for a specific plot.
What is the difference between IS 1893 and IS 13920?
IS 1893 gives the zones and the earthquake forces a structure must be designed for. IS 13920 gives the ductile detailing rules for reinforced concrete so the structure can deform without sudden failure.
Does a low seismic zone mean zero earthquake risk?
No. Zone II means low expected damage risk in the code, not zero. It sets the minimum design requirements, it does not promise safety.
How accurate is the zone in a Geo Prithvi Report?
For India it is an indication based on coordinate ranges that approximate the BIS zone map. It is reliable well inside a zone and less so close to a boundary, where an engineer should confirm it against the official map.