Skip to main content. Search Search. Natural Hazards. Apply Filter. What is a Geoid? Why do we use it and where does its shape come from? Contrast of the Geoid model with an Ellipsoid and cross-section of the Earth's surface. Public domain. Seismometers, seismographs, seismograms - what's the difference? How do they work? A seismometer is the internal part of the seismograph , which may be a pendulum or a mass mounted on a spring; however, it is often used synonymously with "seismograph". Seismographs are instruments used to record the motion of the ground during an earthquake.
They are installed in the ground throughout the world and operated as part of a How can I make my own seismometer? It is relatively easy to acquire the necessary materials and build your own seismometer. The links here are to various sources with information on how to build a seismometer. They range from very simple and inexpensive to sophisticated and pricey. What was the first instrument that actually recorded an earthquake? The earliest seismoscope was invented by the Chinese philosopher Chang Heng in A.
This was a large urn on the outside of which were eight dragon heads facing the eight principal directions of the compass.
Below each dragon head was a toad with its mouth opened toward the dragon. When an earthquake occurred, one or more of the eight dragon What was the duration of the earthquake? Why don't you report the duration of each earthquake?
How does the duration affect the magnitude? The duration of an earthquake is related to its magnitude but not in a perfectly strict sense. There are two ways to think about the duration of an earthquake. The first is the length of time it takes for the fault to rupture and the second is the length of time shaking is felt at any given point e. The earthquake and its impact is measured either by using the Mercalli scale or the Richter Scale.
The two scales, however, each have different applications as well as measurement techniques. The Mercalli scale has been in existence longer dating back to the 19 th century. Its name comes from the modifications made to it in the s by an Italian volcanologist, Giuseppe Mercalli. Ironically, it was Charles Richter who gave the scale its updated form which is used today, presently called the MMI scale, or known as the Modified Mercalli scale.
The Richter scale was developed in by Charles Richter, along with his associate, Beno Gutenberg, and today it is the commonly used scale in earthquake measurement. It was first developed for use in a particular area of California comparing the size of different quakes in the region.
It was later adapted for use around the world. Sometimes not recognized to be an earthquake at first, duration estimated in some cases.
Vibration like that due to passing of light, or lightly loaded trucks, or heavy trucks some distance away. Hanging objects may swing slightly. Movement may be appreciable on upper levels of tall structures. Rocked standing motor cars slightly. Felt indoors by many, outdoors by few. Awakened few, especially light sleepers.
Frightened no one, unless apprehensive from previous experience. Vibration like that due to passing of heavy, or heavily loaded trucks. Sensation like heavy body striking building, or falling of heavy objects to inside. Rattling of dishes, windows, doors; glassware and crockery clink and clash. Creaking of walls, frame, especially in the upper range of this grade.
Hanging objects swing, in numerous instances. Disturbed liquids in open vessels slightly. Felt indoors by practically all, outdoors by many or most. Outdoors direction estimated. Awakened many, or most. Frightened few - slight excitement, a few ran outdoors. Buildings trembled throughout. Broke dishes, glassware, to some extent.
Cracked windows - in some cases, but not generally. Overturned small or unstable objects, in many instances, with occasional fall. Hanging objects, doors, swing generally or considerably. Knocked pictures against walls, or swung them out of place.
Opened or closed, doors, shutters, abruptly. Pendulum clocks stopped, started, or ran fast, or slow. Moved small objects, furnishings, the latter to slight extent. Spilled liquids in small amounts from well-filled open containers. Trees, bushes, shaken slightly. Felt by all, indoors and outdoors. Frightened many, excitement general, some alarm, many ran outdoors. Awakened all. Persons made to move unsteadily. Scientists record responses from many people who experience the earthquake and assign a value from I 1 to XII These numbers are plotted on a map and used to locate the epicenter of the earthquake.
Which waves have the highest velocities? Primary Waves or P-Waves - These are compressional waves, also known as longitudinal waves and are the first seismic waves to arrive at a location on the Earth. This type of wave has the highest velocity for traveling through Earth materials. What does the Richter scale measure? The Richter scale was developed in the s and is most effective for large-scale earthquakes that are of moderate intensity.
The Richter scale measures the maximum amplitude of seismic waves as they reach seismographs. This scale is expressed with a logarithmic scale. How useful is the Mercalli scale? The Mercalli Intensity Scale is only useful for measuring earthquakes in inhabited areas and is not considered particularly scientific, as the experiences of witnesses may vary and the damage caused may not accurately reflect an earthquake's strength.
What are the two scales used to measure earthquakes? There are two primary scales used to measure earthquakes: the Richter scale and the Mercalli scale. The Richter scale is most common in the United States, while worldwide, scientists rely on the Mercalli scale.
The moment magnitude scale is another earthquake measurement scale used by some seismologists.
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