Abstract: A reference structure tomography device is provided which includes a reference structure configured to intercept and modulate energy in the form of waves or otherwise propagating from a source to a sensor, along longitudinal and traverse directions. The reference structure modulates or otherwise conditions the propagating wave to simplify an inversion process on the data set created by the interaction between the wave and the sensors. The reference structure can modulate a wave through multiple types of interactions with the wave including obscuring, defracting, defusing, scattering, and otherwise altering any characteristic of a portion of the wave. By selecting a reference structure that is compatible with the sensors, the number of measurements needed to resolve the source through the source wave is reduced. The reference structure can also increase the resolution of an imaging system.

Abstract: A seismographic sensor is constructed from a D'Arsonval movement. The elements of the movement include a coil suspended in the field of a permanent magnet and a pointer attached to the coil. A weight is attached to the pointer and acts as an inertia element. Leveling screws are provided to control the period of the weighted pointer and to control the resting position of the pointer. When the base of the meter vibrates during an earthquake, the weighted pointer does not follow the vibration because of its inertia, resulting in a relative rotation of the meter coil and the magnet field, thereby inducing a voltage in the coil. This voltage is proportional to one component of horizontal velocity of the earth's motion. Means are provided to process and record the magnitude of this voltage.