SEISMIC

Earthquake / Seismic Zones (II-V)

Zone II (least)-V (most) per IS 1893

Also calledearthquake zoneseismic zonezone 2zone 3zone 4
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IS 1893
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Earthquake Zones of India — IS 1893 Seismic Map & Guide
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seismic zones
Definition

India is divided into four seismic zones — II, III, IV, and V — by IS 1893 Part 1:2016 based on the maximum considered earthquake acceleration. Zone V (highest hazard, Z = 0.36g) covers the entire Himalayan belt, all of the Northeast, the Bhuj region of Gujarat, and the Andaman/Nicobar Islands. Zone IV (Z = 0.24g) covers Delhi NCR, Punjab, the Indo-Gangetic plain north of Bihar, parts of Maharashtra and Sikkim. Zone III (Z = 0.16g) covers most of the central peninsula including Mumbai, Chennai, Kolkata, and most of West Bengal/Odisha/Andhra coast. Zone II (Z = 0.10g) is the lowest, covering Bangalore, Hyderabad, and most of the Deccan plateau.

The zone factor Z is the peak ground acceleration (in units of g) for the maximum considered earthquake — the design spectrum of IS 1893 Cl. 6.4 effectively halves this for design earthquake (Cl. 6.4.2). The zonation reflects historical seismicity, recurrence intervals, and geological understanding from the 1966 first edition through major revisions in 1984, 2002, and 2016. The 2002 revision after the Bhuj earthquake was particularly significant — it added Bhuj to Zone V and elevated several borderline regions. The 2016 edition introduced the design earthquake / maximum considered earthquake distinction explicitly.

The zone determines mandatory ductile detailing requirements via IS 13920:2016 — applicable in Zones III/IV/V for any RC moment frame. In Zone IV/V, irregular buildings (vertical or horizontal) must be analysed by dynamic methods (response spectrum or time history) per Cl. 7.8, not equivalent static. Importance factor I = 1.5 applies in Zones IV/V for hospitals, fire stations, schools, communications buildings, and any structure deemed critical to post-disaster recovery. Building codes for liquid-retaining tanks (IS 1893 Part 2), bridges (IS 1893 Part 3), and industrial structures (IS 1893 Part 4) reference the same zoning map.

Typical values
Zone IIZ = 0.10g — Bangalore, Hyderabad, most of Deccan
Zone IIIZ = 0.16g — Mumbai, Chennai, Kolkata, Pune
Zone IVZ = 0.24g — Delhi NCR, Punjab, parts of Maharashtra
Zone VZ = 0.36g — Himalayas, Northeast, Bhuj, Andamans
Design ground accelerationZ/2 × I/R × Sa/g (Cl. 7.5)
Where used
  • Determining design seismic load Vb per IS 1893 Cl. 7.5
  • Triggering ductile detailing per IS 13920 (Zone III+ for RC frames)
  • Setting importance factor for critical buildings in Zone IV/V
  • Mandating dynamic analysis for irregular buildings in Zone IV/V
  • Liquid-retaining and bridge design via IS 1893 Parts 2 and 3
Acceptance / threshold
Per IS 1893 Part 1 Annex A: each city/district has its zone classification; latest map prevails. Buildings in Zones III/IV/V must follow IS 13920 ductile detailing; storey drift limit 0.004h applies in all zones.
Site example
Site reality: a Pune commercial project was originally classified by an outdated 2002-edition map putting Pune in Zone III. The 2016 IS 1893 Annex A confirmed Pune at Zone III as well, but the structural engineer correctly noted the city's proximity to the Koyna fault and recommended designing for Zone IV (Z = 0.24) as a precaution. The 1.5× higher base shear added 6% to RCC reinforcement cost and 4% to overall structure cost — a cheap insurance premium for an industrial-and-IT hub. Engineers should not blindly use the IS 1893 zone if local fault-line studies suggest higher hazard.
Frequently asked
Which seismic zone is Mumbai/Delhi/Bangalore in?
Per IS 1893 Part 1:2016 Annex A: Mumbai — Zone III (Z = 0.16). Delhi NCR — Zone IV (Z = 0.24). Bangalore — Zone II (Z = 0.10). Kolkata — Zone III. Chennai — Zone III. Hyderabad — Zone II. Pune — Zone III. Ahmedabad — Zone III. Bhuj — Zone V (Z = 0.36). Latur — Zone III. Srinagar — Zone V.
What is the difference between Zone II, III, IV, and V?
The zones reflect different design ground accelerations: Zone II (Z = 0.10g), Zone III (Z = 0.16g), Zone IV (Z = 0.24g), Zone V (Z = 0.36g). Higher zone = higher design seismic force on the building. Each zone also triggers stricter detailing (IS 13920 ductile detailing mandatory in Zone III+) and analysis requirements (dynamic analysis for irregular buildings in Zone IV/V).
Is ductile detailing required in Zone II?
Per IS 1893 Part 1:2016 Cl. 6.1.2, IS 13920 ductile detailing is mandatory only in Zones III, IV, and V. In Zone II it is recommended but not mandatory for ordinary buildings; mandatory for critical buildings (I = 1.5) regardless of zone. Best practice in Zone II for any framed building is to apply at least IS 13920's column-stronger-than-beam principle and provide minimum confining stirrups at beam-column joints.
Related seismic terms
Ductile Detailing (Seismic)
Special seismic detailing per IS 13920
Base Shear
Horizontal seismic force at the base of a structure. Vb = Ah × W, where Ah = (Z/2)(I/R)(Sa/g). IS 1893 Cl. 7.5.
Response Spectrum
Plot of peak structural response vs. natural period for an earthquake. IS 1893 Fig. 2 gives design spectra for 5% damping.
Importance Factor (I)
Multiplier on seismic force based on building criticality. Hospitals: 1.5. Schools: 1.5. Residential: 1.0.
Response Reduction Factor (R)
Reduces elastic seismic forces to design forces accounting for ductility. SMRF: 5.0. OMRF: 3.0. Shear wall: 4.0.
Special Moment Resisting Frame (SMRF)
Frame designed and detailed for high ductility per IS 13920. R = 5.0. Required in Zone IV/V for important buildings.
Soft Storey / Stilt Floor
Storey with stiffness <70% of the storey above — typical of stilt parking. IS 1893 Cl. 7.10 mandates 2.5× design force.
Soil-Structure Interaction (SSI)
Interaction between flexible soil and structure under earthquake. Considered for tall buildings on soft soils per IS 1893.