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).
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.
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.
Tectonic plates are under constant stress from their edges (ridge push and slab pull). In stable "cratons," this stress usually does nothing. However, if there is an old scar in the crust, like the New Madrid Seismic Zone in the USA or the Kutch region in India, the stress concentrates there. BecausRead more
Tectonic plates are under constant stress from their edges (ridge push and slab pull). In stable “cratons,” this stress usually does nothing. However, if there is an old scar in the crust, like the New Madrid Seismic Zone in the USA or the Kutch region in India, the stress concentrates there. Because the crust in these stable regions is cold and dense, seismic waves travel much further and with less energy loss than at plate boundaries. This is why intraplate quakes can be felt over thousands of kilometers and cause massive damage in areas not usually prepared for tremors.
Below 300 km, rocks shouldn't be able to store elastic strain; they should "creep" like warm wax. Seismologists believe deep-focus quakes are caused by "transformational faulting," where minerals like olivine suddenly collapse into denser forms (spinel or bridgmanite) under extreme pressure. This suRead more
Below 300 km, rocks shouldn’t be able to store elastic strain; they should “creep” like warm wax. Seismologists believe deep-focus quakes are caused by “transformational faulting,” where minerals like olivine suddenly collapse into denser forms (spinel or bridgmanite) under extreme pressure. This sudden “implosion” or volume change releases energy as seismic waves. Therefore, while Reid’s theory perfectly explains quakes near the surface, the “Deep-focus” mystery requires a more complex understanding of high-pressure mineral physics and thermodynamics.
In 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.
See lessIntraplate earthquakes, like the 1811 New Madrid or 2001 Bhuj quakes, are often caused by:
Tectonic plates are under constant stress from their edges (ridge push and slab pull). In stable "cratons," this stress usually does nothing. However, if there is an old scar in the crust, like the New Madrid Seismic Zone in the USA or the Kutch region in India, the stress concentrates there. BecausRead more
Tectonic plates are under constant stress from their edges (ridge push and slab pull). In stable “cratons,” this stress usually does nothing. However, if there is an old scar in the crust, like the New Madrid Seismic Zone in the USA or the Kutch region in India, the stress concentrates there. Because the crust in these stable regions is cold and dense, seismic waves travel much further and with less energy loss than at plate boundaries. This is why intraplate quakes can be felt over thousands of kilometers and cause massive damage in areas not usually prepared for tremors.
See lessThe ‘Elastic Rebound Theory’ fails to explain which type of seismic event?
Below 300 km, rocks shouldn't be able to store elastic strain; they should "creep" like warm wax. Seismologists believe deep-focus quakes are caused by "transformational faulting," where minerals like olivine suddenly collapse into denser forms (spinel or bridgmanite) under extreme pressure. This suRead more
Below 300 km, rocks shouldn’t be able to store elastic strain; they should “creep” like warm wax. Seismologists believe deep-focus quakes are caused by “transformational faulting,” where minerals like olivine suddenly collapse into denser forms (spinel or bridgmanite) under extreme pressure. This sudden “implosion” or volume change releases energy as seismic waves. Therefore, while Reid’s theory perfectly explains quakes near the surface, the “Deep-focus” mystery requires a more complex understanding of high-pressure mineral physics and thermodynamics.
See less