PRESENTATION ON

RESERVOIR INDUCED SEISMICITY

Made By:Sachin RaturiCivil Engg.DIT University

RESERVOIR INDUCED SEISMICITY Reservoir induced seismicity

refers to triggering of earthquake

due to impounding of an

artificial reservoir.

Mechanism Of RIS

Filling Of Reservoir

• Reservoir Filling Increases The Vertical Stress Over The Underlying Saturated Rock Strata Further Increasing The Pore Water Pressure There.

Increase In Pore Water Pressure In Underlying Strata

• Increased Pore Water Pressure Reduces The Net Effective Stress Along The Fault Plane.

• NORMAL EFFECTIVE STRESS = NORMAL STRESS – PORE WATER PRESSURE

Shear Failure of Underlying Rock

Strata

• Shear Fracturing Occurs Along Fault Plane Leading To Earthquake.

MISCONCEPTIONS REGARDING RIS

RIS is caused due to weight of water.

Occurrence of a fault in underlying strata of reservoir as a mandatory condition for RIS.

RIS do not occur along inactive fault.

MAJOR CASES OF RIS IN WORLD

LOCATION MAGNITUDE YEAR

1. Aswan, Egypt 5.3 1981

2. Latur, India 6.1 1993

3. Koynanagar, India 6.3 1967

4. Monticello, USA <4.5 1978

5. Yantan, China 3.5 1994

Koyna Earthquake Start of impounding of reservoir – 1963

Date of occurrence of earthquake – 10 December, 1967

200 people lost their lives.

80% of the Koyna township was razed.

Uniqueness Of Koyna EarthquakeRegistered largest RIS event on the globe.

Still continues to exhibit RIS.

More than 400 cases of earthquake have been recorded.

Shows a relationship between height of reservoir and frequency and magnitude of earthquake registered.

Understanding Correlation Between Height of Reservoir and Earthquake in Koyna

Year Change In Reservoir Effect on Seismicity

Sept 1968 – Jan 1968 Water level kept maximum. Earthquake of magnitude 6.3 on

10 December,1967.

Feb1968 - Aug1973 Water level at minimum. No significant seismic event.

Sept 1973 Water level again raised to maximum. Earthquake of magnitude 5.1 was

registered on 17 October, 1973.

Conclusion : Seismic activity increased with increase in level

of reservoir.

FACTORS AFFECTING RIS

Presence of fault in vicinity of reservoir.

Subsurface geology of reservoir.

Type of fault(Strike slip or Normal).

PRECAUTIONS TO BE TAKEN TO AVOID RIS Acceptability of phenomena of RIS and carrying out

pre construction surveys accordingly.

Avoiding design of large reservoirs for case of areas where faults are present.

Suitable treatment of sub surface geological features such as faults.

Carefully examining areas where reservoir area is surrounded by pervious rocks and judging suitability of project accordingly.