Continental Mantle Earthquakes
Why in News?
- A Stanford University study, published, mapped 459 such earthquakes worldwide using advanced detection methods, sparking global interest.
- This research highlights their regional clustering under areas like the Himalayas and Bering Strait, challenging views on mantle ductility. The findings aid in understanding deep Earth mechanics amid ongoing seismic monitoring.
Key Features
- Origin & Depth: Unlike typical earthquakes that occur in the brittle crust (10–30 km depth), CMEs originate more than 80 km below the Mohoroviฤiฤ discontinuity (Moho)—the boundary separating the crust from the mantle.
- Regional Clusters: While rare, these quakes are not random. Major clusters are found beneath:
- The Himalayas: High concentration due to the intense collision between the Indian and Eurasian plates.
- The Bering Strait: A region with complex tectonic stress between Asia and North America.
- Other Areas: Clusters also appear under the Tibetan Plateau, East Africa, Alaska, and the Caucasus.
- Trigger Mechanisms: Scientists are exploring two primary theories:
- Stress Transfer: Intense pressure from crustal earthquakes or continental collisions may penetrate deep into the mantle.
- Mantle Convection: Heat-driven circulation of rock within the mantle itself may cause sudden ruptures.
- Surface Impact: Because they occur at such extreme depths, CMEs typically do not cause significant shaking or danger at the Earth's surface.
- Scientific Significance:
- Lithosphere Dynamics: They show that the crust and mantle behave as an interconnected system rather than independent layers.
- Internal Probes: These quakes act as natural sensors, providing clues about the internal temperature, composition, and structure of the Earth's deep interior.
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