Yuji Otake, Akito Araya and Kazuo Hidano ERI, Earthquake Research Institute University of Tokyo Development of a Highly-sensitive/ Broad-band Servo-type Seismometers using Magnetic Levitation Development of a Highly-sensitive/ Broad-band Servo-type Seismometers using Magnetic Levitation

Earth To observe cheaply easily the vertical/Horizontal components of normal free oscillations of the Earth at many points. To observe Telseismic Events Earthquake Use for Earth Tomography m/s Less than 0.1 Hz Seismometer Purpose of Development Less than m/s Less than 0.01 Hz Atmospheric Pressure Normal Free Oscillations

By using the NS alternative magnetization, we can obtain a uniform potential energy just above the magnet surface. A perpendicular direction referred to the movement direction of a pendulum must be mechanically constrained with a hinge, because of Earnshaw’s low. Levitation A horizontal component seismometer with magnetic levitation using plane permanent magnets with NS alternatively magnetized strips. A horizontal component seismometer with magnetic levitation using plane permanent magnets with NS alternatively magnetized strips.

A principle of an astatic rotational pendulum using a plunger permanent magnet in a uniform magnetic field environment. A principle of an astatic rotational pendulum using a plunger permanent magnet in a uniform magnetic field environment. The positive rotational moment of a plunger permanent magnet generated by a magnetic field B cancels a negative rotational moment acted at a weight by gravity.

The vertical component seismometer using an astatic rotational pendulum The vertical component seismometer using an astatic rotational pendulum Capacitance Position Sensor Feedback Coil Magnetic Spring Pendulum Weight Window-frame Magnet Plunger Magnet Free oscillation Natural Period : about 5s

The wave form and the frequency spectrum of the earth ’ s background vibration noise at Matushiro, March 04 ” The wave form and the frequency spectrum of the earth ’ s background vibration noise at Matushiro, March 04 ” buoyancy Marine Microseism m/s March 12, 04 ” AM 2h 2min 10 - ８ (m/s)/√Hz Rotational Pendulum (m/s)/√Hz 10**-5 10**-4 10**-6 10**-7 10**-8 10**-9 10**-10 10**-3 10**-2 10**-3 10**-110**-010**110**2 Frequency [Hz]

The details will be presented in the poster. summary 1.We proofed the principle of the vertical astatic rotational pendulum. 2. The noise level of the rotational pendulum seismometer in a frequency range over 1 Hz was less than (m/s)/√Hz.