Vicentini (1895 and 1899)Let's go back to the early days, and take a look at a contemporary of the Reuber-Paschwitz and Reuber-Ehlert seismographs. The Vicentini instruments are simple, un-damped pendulums, one to record the two horizontal components of motion, and another to record the vertical component. The clock at the back of the image above is a precision chronometer that was used to produce...

Mainka (1910)The Mainka seismograph is a large, single component horizontal pendulum (two instruments installed at right angles to each other are required to fully describe the horizontal ground motion).Its 450kg mass is suspended in such a way that it oscillates around a near-vertical axis, with a natural period of 8-10 seconds. Damping is provided by a dash-pot system (a plate moving through a vi...

Wiechert vertical seismograph (1909)The Wiechert vertical seismograph was built in Göttingen, Germany, in 1909, five years after the horizontal seismograph described in last week's post. The two instruments together formed a complete recording system, capable of determining the 3 components of ground motion.The vertical seismogram has a mass of 1200 kg and a natural period of 5 seconds. Its design...

Wiechert horizontal seismograph (1904)The Wiechert horizontal seismograph (built in Göttingen, Germany, in 1904) has an unusual and striking design: it is essentially an inverse pendulum weighing 1 ton, in unstable equilibrium about a universal pivot at its base. Its natural period is 8 seconds.The horizontal motion of the mass with respect to the casing is decomposed into its two perpendicular co...

The earthquake that occurred last Friday June 13th in Eastern Honshu, Japan - a M6.8 event according to the USGS, a M7.0 event according to JMA - occurred in a relatively lightly populated area, and caused few fatalities. Most of the damage seems to have been caused by landslides following the event (see Dave's landslide post).In October 2007, Japan launched its Earthquake Early Warning system, mea...