The seismometer aims to record the seismic waves spread in the crust of the planet Mars. InSight's robotic arm has just installed a jackhammer right next to itself.
Because the seismic waves are refracted or reflected at the boundaries of the layers during transmission, changes in the velocity of the seismic waves and the thickness of the layers can be estimated.
Although the State University of New York(SUNY), USA is a global leader in measurement techniques of such seismic velocities, their highest measurement pressure was limited to~10 GPa.
They revealed that the discontinuity and anisotropy of the seismic waves at the boundary between the core and mantle can be consistently explained if the existence of post-perovskite is assumed.
We conducted many tests based on more than ten types of earthquake waves that occurred in the past, such as inland earthquakes and subduction-zone earthquakes, and confirmed the seismic isolation effect for all earthquake waves.
An elasticity tensor is a set of proportional constants that represent the magnitude of stresses when a mineral is deformed. Additionally, the elasticity tensor is an index of the hardness of a mineral and determines the velocity of seismic waves.
Seismic waves such as P-waves and S-waves, which can be observed on the ground, are clues about the conditions in Earth's interior. Depth-dependent propagation velocities of seismic waves have been determined with a high degree of accuracy.
In recent years, the techniques to analyze seismic waves have remarkably progressed. Image analysis, called seismic wave tomography, which utilizes large-scale computers to analyze data collected from seismometers placed worldwide, has become very popular.
This discovery revealed that the"post-perovskite" in the D" layer is a layered crystal structure, and that this has a major influence on seismic wave propagation and mantle convection, as well as rotational movement, etc.
To resolve this dispute, high-pressure, high-temperature conditions equivalent to the transition zone must be reproduced. Then the velocities of these experimentally produced seismic waves(elastic waves) must be compared to actual seismic waves(elastic waves) measured on the ground.
During a four-day experiment in Monterey Bay, the researchers recorded a 3.5 magnitude quake from an underwater fault zone which had occurred 45 kilometers away and used the seismic waves from it to discover a new underwater fault system.
Their research group was the first to successfully determine the seismic wave velocities in ringwoodite and majorite under conditions at up to~20 GPa and 1,400 °C, which are equivalent to those in the mantle transition zone Fig.
With its global network of nearly 300 seismic, hydroacoustic, infrasound and radionuclide detecting stations, the CTBTO has made it much harder for states to conduct covert nuclear tests- be they in the atmosphere, underground, or underwater.
We will also study the effects of nickel and light elements considered to be present in the inner core on its density and the velocity of seismic waves to determine the chemical composition of the inner core. Using this data, we will also try to determine the chemical composition of the outer core.
Specifically, he is doing research such as three-dimensional estimation of the structure of the propagation velocity of seismic waves in the Earth interior by using seismic wave tomography, cooperating with seismologists all around the world and Christine Houser, a member of ELSI.
They also quantified frictional properties of faults in rotary-shear friction experiments and performed dynamic rupture simulations by using their experimentally-obtained friction parameters, establishing a method for evaluating the potential of coseismic fault slip and properties of seismic waves generated from the fault.
Currently, their research group is developing new technologies to measure seismic velocities under conditions exceeding 25 GPa to explore materials in even deeper parts of the lower mantle as well as to measure the seismic velocities of oceanic crustal materials, which are other types of constituent materials of the plates.
The SGI president lauds the IMS:"Its core function was again demonstrated in the rapid detection of the seismic waves and radiation from the recent(January 6) North Korean nuclear test. In addition, the global IMS network has been used to gather data about natural disasters and the impact of climate change.
Seismic wave tomography has revealed the state of the subducted plates directly under the Japanese islands, which exist near the mantle transition zone. However, because the seismic wave velocity of the mantle transition zone and that of each plate material are unknown, seismic wave analyses could not identify specific rocks minerals.
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