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Which of the following explains the cause of earthquakes occurring on the eastern margins of Asia?
The eastern coast of Asia is a classic "convergent boundary." The Pacific Plate is moving westward and diving under the Eurasian Plate at a rate of several centimeters per year. This process, called subduction, creates the deepest parts of the ocean (like the Mariana Trench). The friction between thRead more
The eastern coast of Asia is a classic “convergent boundary.” The Pacific Plate is moving westward and diving under the Eurasian Plate at a rate of several centimeters per year. This process, called subduction, creates the deepest parts of the ocean (like the Mariana Trench). The friction between these two colossal slabs of crust is immense. When the “stuck” plates finally slip, it results in some of the most powerful earthquakes in history, such as the 2011 Tohoku earthquake. This subduction also melts the crust, feeding the chain of volcanoes that make up the islands of Japan and the Philippines.
See lessWhich seismic wave is characterized by a purely horizontal, side-to-side motion perpendicular to the direction of travel?
Named after Augustus Edward Hough Love, these waves are "trapped" at the Earth's surface. While S-waves also move perpendicular to travel, Love waves are restricted to the surface and travel slightly faster than Rayleigh waves. Their motion is purely parallel to the surface, essentially "shaving" thRead more
Named after Augustus Edward Hough Love, these waves are “trapped” at the Earth’s surface. While S-waves also move perpendicular to travel, Love waves are restricted to the surface and travel slightly faster than Rayleigh waves. Their motion is purely parallel to the surface, essentially “shaving” the ground back and forth. Because they have a high amplitude and occur at the surface where human infrastructure exists, they are the primary cause of the foundation failures and horizontal “whiplash” damage seen in high-magnitude earthquakes.
See lessThe ‘Shadow Zone’ for P-waves exists because of which physical process at the Core-Mantle Boundary (CMB)?
When P-waves hit the Gutenberg Discontinuity, the change from solid silicate rock to liquid iron-nickel causes a dramatic change in wave speed. Following Snell’s Law, the waves are refracted inward. Consequently, they are diverted away from the 103°–143° region, creating the P-wave shadow zone. UnliRead more
When P-waves hit the Gutenberg Discontinuity, the change from solid silicate rock to liquid iron-nickel causes a dramatic change in wave speed. Following Snell’s Law, the waves are refracted inward. Consequently, they are diverted away from the 103°–143° region, creating the P-wave shadow zone. Unlike S-waves, which are blocked entirely by the liquid, P-waves eventually emerge beyond 143°, but the refraction pattern leaves a definitive “silent zone.” Analyzing this specific shadow zone was crucial for scientists to calculate the exact size and depth of the Earth’s core.
See lessIn a subduction zone, the planar zone of seismicity produced by the down-going oceanic plate is called the: (A) Mohorovičić Zone (B) Gutenberg Zone (C) Wadati-Benioff Zone (D) Richter Zone
This zone is characterized by shallow-focus earthquakes near the trench, intermediate-focus quakes further inland and deep-focus quakes at the furthest extent. As the brittle oceanic slab descends into the hotter, more plastic mantle, it remains cool enough to fracture and generate earthquakes for aRead more
This zone is characterized by shallow-focus earthquakes near the trench, intermediate-focus quakes further inland and deep-focus quakes at the furthest extent. As the brittle oceanic slab descends into the hotter, more plastic mantle, it remains cool enough to fracture and generate earthquakes for a few hundred kilometers. Beyond 700 km, the rock becomes too hot and ductile to break, ending the seismic zone. Mapping these zones allowed geologists to confirm the theory of Plate Tectonics and understand the geometry of subduction angles around the Pacific Ring of Fire.
See lessWhat is the phenomenon where seismic waves are amplified due to soft, water-saturated sediments, causing the ground to behave like a fluid?
This is a major hazard in coastal areas or river basins with sandy, loose soil. During an earthquake, the vibrating motion compacts the soil particles, pushing the water trapped between them upward. This pore-water pressure becomes high enough to support the weight of the soil, turning solid groundRead more
This is a major hazard in coastal areas or river basins with sandy, loose soil. During an earthquake, the vibrating motion compacts the soil particles, pushing the water trapped between them upward. This pore-water pressure becomes high enough to support the weight of the soil, turning solid ground into a slurry. This was famously seen in the 1964 Niigata earthquake and the 2011 Christchurch quake. Once the shaking stops, the water drains and the soil settles, often leaving “sand volcanoes” on the surface as evidence of the high-pressure water escape.
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