Four hours after the first shocks, waves as high as 16 metres inundated the coast and carried one US gunboat two miles inland to rest precariously on the edge of a 60m cliff. The only North American account of one of the continent's largest earthquakes comes from the oral history of native Americans near Vancouver island which describes how the large community of Pachena bay was wiped out by a huge wave. Across the pacific, the quake was accurately recorded by Japanese observers of the large tsunami that struck Japan on 27 January The power of that inundation has been used by historians and seismologists to pinpoint the magnitude of the Vancouver quake.
Emanating from the ocean off Ecuador and Colombia, the quake generated a tsunami that killed between and 1, people along a coastline from Central America to San Francisco. To the west in Hawaii, rivers suddenly drained about 12 hours after the first shocks, then were submerged as a series of successively larger waves flooded the coast. The near-total destruction of Lisbon and the deaths of a quarter of the city's population were caused by an earthquake, followed by a tsunami and fire, that was felt in north Africa, France and northern Italy.
In the age of enlightenment, the cultural impact of the quake spread even further afield as the horrors of Lisbon provided inspiration for sensationalist artworks and philosophical tracts. Voltaire penned a poem on the catastrophe and scientists found a wealth of written first-hand accounts to advance their understanding of the physical world. How s trong an e arthquake f eels to an o bserver d epends o n d istance to the q uake , subsurface geology, whether one is in a building or not, and what type of building one is in, and the observer.
Scientists rely on a recording instrument known as a seismograph to determine the magnitude, defined as a measure of the strength of an earthquake or strain energy released by it. A simple seismograph consists of a pen or pencil, suspended on a spring or other moveable item, which makes a mark on a piece of paper.
A Chinese philosopher, Chang Heng, invented one of the first mechanical means of detecting earthquakes, in AD. It was a cast bronze vessel with a domed lid, resembling a wine jar, around which sat eight dragons, each a holding a ball in its mouth. When an earthquake hit, one or more of the dragons dropped a ball into the mouth of a toad sitting below the dragon.
English scientists working in Japan developed the first modern seismograph between and More complicated seismographs use sensors called seismometers , which can detect ground motions caused by seismic waves from both near and distant earthquakes.
Some seismometers are capable of detecting ground motion as small as 0. One nanometer is 1 billionth of a meter or about 39 billionths of an inch. Seismometers measure vertical motion and horizontal motion in north-south and east-west direction. Shaking causes the recording instrument to move, which produces a mark on paper, film, or recording tape.
This is known as a seismogram. The bigger the quake the larger the size or amplitude of the waves recorded. Probably the best-known gauge of earthquake intensity is the local Richter magnitude scale, developed in by United States seismologist Charles F. Just crouch down and wait for chances. Even if the nest is collapsed, some eggs in it may still be kept intact.
In fact, it mirrors the advice the USGS gives today. Running during an earthquake is very dangerous and being inside can protect you from flying debris. But if you see something that doesn't look right, click here to contact us! Twice a week we compile our most fascinating features and deliver them straight to you.
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