IS 4967:1968 is the Indian Standard (BIS) for recommendations for seismic instrumentation for river valley projects. This standard provides guidelines for the selection, location, installation, and maintenance of seismic instruments in river valley projects, particularly large dams. It ensures that ground motion and structural response during earthquakes are accurately recorded for safety evaluation and future design improvements.
Recommendations for seismic instrumentation for river valley projects
| Parameter | IS Value | International | Source |
|---|---|---|---|
| Primary Instrument Type | Strong Motion Accelerograph (Analog, on film), Seismoscope | Digital Strong Motion Accelerograph with tri-axial sensors and networking | ICOLD Bulletin 122:2002 |
| Recording Medium | Photographic film, smoked glass | Solid-state digital memory with telemetry options | USACE EM 1110-2-4300:2021 |
| Typical Trigger Threshold | 0.01g (10 Gal) | 0.001g - 0.005g (Site-specific, with pre-event memory) | USACE EM 1110-2-4300:2021 |
| Time Synchronization | Not specified; internal timing marks | GPS synchronization to microsecond accuracy across the network | ICOLD Bulletin 122:2002 |
| Minimum Instruments (Large Concrete Dam) | One at top, one in foundation gallery, one in free-field. | Minimum array of 5+ instruments to define structural modes (crest, mid-height, galleries, abutments, free-field). | ICOLD Bulletin 122:2002 |
| Free-Field Instrument Location | At a distance of about two to three times the height of the dam. | At least 3 times the structure height, on representative foundation material, away from topographic effects. | USACE EM 1110-2-4300:2021 |
| Post-Earthquake Data Use | Collection and processing of records for study. | Automated retrieval and processing for immediate structural safety assessment. | CDA Dam Safety Guidelines: 2013 |