Handbook›Seismic Zone Data (IS 1893)

Seismic Zone Data (IS 1893)

IS 1893 (Part 1) : 2016 · Clause 6.4 — Zone Factor (Table 3) & Annex A — Seismic Zone Map

India is divided into 4 seismic zones (II to V). Zone factor (Z) is used to calculate design seismic base shear. IS 1893 was revised in 2016 — Zone I was merged into Zone II.

IS 1893 →

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Seismic Zone Factors (IS 1893 Table 3)

Z = Zone Factor = Effective Peak Ground Acceleration (as fraction of g)

Zone / City	Z Factor	Intensity	Risk / State	Examples
Zone II (Low)	0.10	VI (or less)	Low damage risk	South & Central Peninsula
Zone III (Moderate)	0.16	VII	Moderate damage risk	Mumbai, Kolkata, Chennai, Jaipur
Zone IV (Severe)	0.24	VIII	High damage risk	Delhi, Patna, Lucknow, most of NE
Zone V (Very Severe)	0.36	IX (or more)	Very high damage risk	Kashmir, NE India, Kutch, Uttarakhand

Major Cities — Seismic Zone

Zone / City	Z Factor	Intensity	Risk / State	Examples
Ahmedabad	III	0.16	Gujarat	After 2001 Bhuj earthquake
Bangalore / Bengaluru	II	0.10	Karnataka
Bhopal	II	0.10	MP
Bhubaneswar	III	0.16	Odisha
Chandigarh	IV	0.24	Punjab
Chennai	III	0.16	Tamil Nadu
Delhi / NCR	IV	0.24	Delhi	High risk — near Himalayan plate boundary
Guwahati	V	0.36	Assam	NE India — highest zone
Hyderabad	II	0.10	Telangana
Jaipur	II	0.10	Rajasthan
Kochi	III	0.16	Kerala
Kolkata	III	0.16	West Bengal	Soft soil amplification risk
Lucknow	III	0.16	UP
Mumbai	III	0.16	Maharashtra
Nagpur	II	0.10	Maharashtra
Patna	IV	0.24	Bihar	Indo-Gangetic plain — soft soil
Pune	III	0.16	Maharashtra
Shimla	IV	0.24	HP	Himalayan zone
Srinagar	V	0.36	J&K	Himalayan zone
Thiruvananthapuram	III	0.16	Kerala
Varanasi	III	0.16	UP
Visakhapatnam	II	0.10	AP

Importance Factor (I) — IS 1893 Table 8

Multiplied with base shear — higher I = more conservative design

Zone / City	Z Factor	Intensity	Examples
Residential, Commercial, Office	1.0	Normal	Standard buildings
Schools, Assembly halls, Cinemas	1.2	Important	Large occupancy
Hospitals, Fire stations, Emergency	1.5	Critical	Post-earthquake functionality
Nuclear, Dams, Large bridges	1.5–2.0	Lifeline	Special structures — as per specific IS codes

Response Reduction Factor (R) — IS 1893 Table 9

Higher R = more ductile system = lower design forces

Zone / City	Z Factor	Intensity	Examples
Ordinary RC Moment Frame	3.0	Low ductility	Not permitted in Zone IV, V
Special RC Moment Frame (SMRF)	5.0	High ductility	IS 13920 ductile detailing
Ordinary RC Shear Wall	3.0	Low ductility
Ductile RC Shear Wall	4.0	Medium ductility
Dual System (SMRF + Ductile Wall)	5.0	High ductility	Most high-rise buildings
Steel Moment Frame (SMRF)	5.0	High ductility	IS 800 steel
Steel Braced Frame	4.0	Medium ductility
Unreinforced Masonry	1.5	Non-ductile	Not permitted in Zone III, IV, V
Confined Masonry	3.0	Low ductility	With RC tie columns & bands

Notes

• Base Shear: VB = Z/2 × I/R × Sa/g × W. This is the fundamental seismic design equation.

• Sa/g = spectral acceleration coefficient — depends on time period (T) and soil type (I, II, III)

• Soil Type I = Rock/Hard, Type II = Medium, Type III = Soft. Soft soil amplifies seismic waves.

• IS 1893:2016 removed Zone I — all of India is now Zone II or higher

• In Zone IV & V: ductile detailing per IS 13920 is MANDATORY for all RC frames

• For buildings < 15m in Zone II: seismic analysis may not be critical — but IS 1893 compliance is still required

• Seismic weight includes: full DL + 25% LL (if LL ≤ 3 kN/m²) or 50% LL (if LL > 3 kN/m²)

• Time period for RC frame: T = 0.075 × h^0.75 (h = height in metres)

• Time period for RC shear wall: T = 0.075 × h^0.75 × √(Aw/Ab) — modified by wall area

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