FAQ regarding seismic isolators
We provide the following answers to help you better understand earthquakes and seismic isolation.

Earthquakes are the shocks that occur when bedrock is destroyed.
These shocks come to the surface of the earth as seismic waves, which we feel as earthquakes.
So, what causes bedrock to be destroyed?
Bedrock is also called a "tectonic plate", which is made up of rocks dozens of kilometers in thickness.
The inside of the earth is divided into various tectonic plates and these plates move several centimeters a year in separate directions.
Distortions happen at the place where different plates meet and the power at that point becomes the source of an earthquake.

Magnitude refers to the scale of the earthquake measured at the place where the earthquake was generated.
Seismic intensity refers to the strength of the shaking of the ground surface at a given location. The earthquake travels to various places from the epicenter and is felt at various intensities depending on the location.

There are "epicentral earthquakes" and "subduction-zone earthquakes".
Epicentral earthquakes denote cases when the distortion between plates happens directly below a given location.
On the other hand, subduction-zone earthquakes occur where a tectonic plate meets another tectonic plate and subsides below it towards the earth's core.
As the plate is dragged below force builds to try to return the plates to their original position. A subduction-zone earthquake occurs when enough force builds up such that these two plates rapidly snap back.
Subduction-zone earthquakes are notable for their very large scale. (the Great Kanto Earthquake was such a type)

When an earthquake is generated, the shock radiates out from the epicenter.
The wave of the earthquake has two kinds of waves; a "P wave" (primary wave) and an "S wave" (side wave).
The P wave advances in a straight direction away from the epicenter, shaking the surface vertically along its path, while the S wave vibrates perpendicular to the P wave, shaking the surface horizontally.
Therefore, the P wave arrives at a given location 2 to 3 times faster than S wave. The first smaller shaking is the P wave, followed by the larger shaking of the S wave.

When a shockwave travels out from the epicenter and enters into soft ground from hard ground its "amplitude" increases.
The softer ground the bigger amplitude is. It is thought that an earthquake suddenly grows large and damage becomes more serious on softer ground.

True. There are dislocations of tectonic plates all across Japan.
The "Munich Reassurance" estimation indicates that Tokyo has the most natural disaster risk of 710 points as compared to 30 for London, 25 for Paris, 15 for Beijing, and 42 for New York.
Thus, we must take thorough measures (risk hedge) for earthquakes.

Resonance is caused when external shock triggers natural vibration.
A simple example of resonance is a swinging pendulum.
Once a push activates the pendulum, the pendulum begins vibrating at its natural frequency. The vibration amplitude gradually increases when it is given a push at a period close to a natural vibrating frequency of the pendulum.
However, the amplitude does not increase when it is given a push in a period that is greatly different from the natural frequency.
When an earthquake with the same frequency as the natural vibrating frequency of a seismic isolation device occurs, resonance may occur. In this case, the amplitude of the device is amplified until it exceeds its maximum allowable travel distance and becomes dislocated.
When deciding upon a seismic isolation device, the capability to prevent resonance, which Abserver possesses, is important.

Restoring force is the ability of the device to return to its original position.
Abserver^® realizes this ability by using a change in potential energy.
Damping force is the ability of a device to absorb an input vibration, such as an earthquake, and absorb its energy, control relative displacement between the building floor and device, and to stop vibrating after the earthquake ends.
Abserver^® realizes this damping force through the friction between the oblate spheroid bearing and the top and bottom plates.
It is desirable for seismic isolation devices to realize both damping and restoring forces.

"Anti-seismic" typically refers to making buildings that can withstand earthquakes by enhancing the strength of the structure itself.
"Seismic-control" is achieved by installing a mechanical, rubber or oil damper into a building's frame to absorb shakes.
"Seismic-isolation" is when a device is installed between a base surface and a load to interfere with the transmittance of an earthquake's vibration to the load.

It is not necessary for such buildings.
However, it is necessary for anti-seismic buildings since they are built to withstand earthquakes and are, as such, rigid and end up transferring an earthquake's force to people and objects inside the building.

• Adjustable dampening force via the oblate spheroid bearings, allowing for customization according to load and desired isolation response (such as only responding to a particular scale earthquake).
• Light, simple structure that allows for installation by non-specialists.
• Coexistence of Damping and Restoring forces (which is rare)
• Does not require maintenance after installation.
• Lower price

Because the device moves in a pendulum motion, the restoring force does not depend on the load.
As the damping force relies on frictional force, enough performance is shown even if load is lightweight.

Because seismic intensity changes according to properties of the ground below and building above, it is difficult to express it in scale of seismic intensity but it should function properly up until the intensity that would cause a normal building to collapse.

We know that the effect of earthquake vertical motion is considerably lower than horizontal motion. Even if vertical motion at the peak is added to the earthquake horizontal motion, it is recognized that there is only an increase effect of several percents.
The optional rigid rubber mat does increase performance against vertical shocks.

Vibration experiments have been performed by and authorizations/patents awarded by the following institutions.

• Three-dimensional vibration experiment in UR Institute of Housing Technology
• Academic papers by Tokyo Metropolitan University, Tokyo Metropolitan College of Industrial Technology
• Cooperative Business Authorization by the Ministry of Economy, Trade and Industry's Kanto Department
• Authorized Industrial Revitalization Project by Shinagawa Ward of Tokyo
• Authorized Product requisitioned by the Tokyo Metropolitan Government
• Supported project of the National Federation of Small Businesses
• Industry-university joint development project of the Metropolitan University of Tokyo
• PAT No.2878626 Damping Force of the rolling with the marble bearing
• PAT No.3249451 Restoring Force of the rolling with the marble bearing
• PAT No.3340707 Seismic Isolation by Damping Seat Pad
• PAT No.2006-283959 Seismic Isolation Device by marble bearing