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Which region experiences ‘Megathrust’ earthquakes? (A) Mid-Atlantic Ridge (B) East African Rift (C) Subduction Zones (D) San Andreas Fault
Because the contact area between two subducting plates is massive (hundreds of kilometers long and wide), it can store an incredible amount of elastic energy. When this "megathrust" finally slips, the energy release is equivalent to thousands of atomic bombs. All of the top 10 largest earthquakes inRead more
Because the contact area between two subducting plates is massive (hundreds of kilometers long and wide), it can store an incredible amount of elastic energy. When this “megathrust” finally slips, the energy release is equivalent to thousands of atomic bombs. All of the top 10 largest earthquakes in recorded history, including the 1960 Chile (9.5) and 2011 Japan (9.1) quakes, were megathrust events. These boundaries are also unique because they involve vertical seafloor movement, making them the primary source of trans-oceanic tsunamis.
See lessThe ‘Richter Scale’ is a measure of magnitude based on: (A) The total area of the fault. (B) The maximum amplitude of the S-wave recorded on a specific seismograph. (C) The number of buildings destroyed. (D) The duration of the shaking in minutes.
The Richter scale was the first successful attempt to give a single number to an earthquake's size. However, because it only measures one peak on a seismogram, it doesn't account for the "total" energy of very long-duration quakes. It is a "Local Magnitude" scale. While the public still uses the terRead more
The Richter scale was the first successful attempt to give a single number to an earthquake’s size. However, because it only measures one peak on a seismogram, it doesn’t account for the “total” energy of very long-duration quakes. It is a “Local Magnitude” scale. While the public still uses the term “Richter,” scientists have largely moved to the Moment Magnitude Scale, which looks at the physical “work” done by the fault. Still, the Richter scale’s logarithmic logic remains the foundation for how we perceive and communicate earthquake power today.
See lessIn seismology, ‘Attenuation’ refers to:
Think of attenuation as the "muffling" of sound as you move away from a speaker. In the Earth, waves lose energy every time they move a particle of rock. Soft, hot or fractured rocks (like those near volcanic arcs) attenuate waves very quickly. Conversely, old, cold and solid "cratons" have low atteRead more
Think of attenuation as the “muffling” of sound as you move away from a speaker. In the Earth, waves lose energy every time they move a particle of rock. Soft, hot or fractured rocks (like those near volcanic arcs) attenuate waves very quickly. Conversely, old, cold and solid “cratons” have low attenuation, allowing seismic energy to travel great distances. This is why a magnitude 6.0 earthquake in the Eastern US (low attenuation) is felt over a much larger area than a 6.0 in California (high attenuation/fractured crust).
See lessWhich instrument is used specifically to measure the tilting or ‘bulging’ of the ground before an earthquake?
Tiltmeters act like highly advanced carpenter's levels. They often use a bubble of gas in a liquid or a laser system to track changes in the Earth's slope to within a fraction of a millimeter. While they cannot predict when an earthquake will happen, they are essential for monitoring "geodetic" chanRead more
Tiltmeters act like highly advanced carpenter’s levels. They often use a bubble of gas in a liquid or a laser system to track changes in the Earth’s slope to within a fraction of a millimeter. While they cannot predict when an earthquake will happen, they are essential for monitoring “geodetic” changes. In volcanic regions, a rising tiltmeter reading suggests that magma is inflating the mountain, while along a fault, it indicates that the plates are bending under extreme elastic strain, providing vital data for hazard assessment and long-term monitoring.
See lessWhich layer of the Earth acts as a ‘Low Velocity Zone’ (LVZ) for seismic waves?
The LVZ exists between depths of about 100 to 250 km. The presence of a tiny percentage of melt (liquid) between the crystal grains of the peridotite rock makes the asthenosphere less rigid. Since seismic wave speed is directly related to the rigidity of the material, they slow down. This discoveryRead more
The LVZ exists between depths of about 100 to 250 km. The presence of a tiny percentage of melt (liquid) between the crystal grains of the peridotite rock makes the asthenosphere less rigid. Since seismic wave speed is directly related to the rigidity of the material, they slow down. This discovery was vital because it explained how tectonic plates (the rigid lithosphere) are able to slide across the Earth’s surface—they are literally “lubricated” by the more pliable, low-velocity asthenosphere layer below.
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