| Seismogram Gallery |
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| global (teleseismic) events | local and regional events | noise and other signals |
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KERMADEC ISLANDS REGION Time: 00/04/11 06:41:26 Location: 27.90S 178.41W Magnitude: 5.6 |
Description: Mag. 5.6 is about as small an earthquake as can be seen in New York from this very active region of the South Pacific. A clear sign of its distance is the long time between the small body wave signals (left) and the larger rayleigh wave arrivals (right). |
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MICHOACAN, MEXICO Time: 00/04/11 18:35:39 Location: 18.26N 102.36W Magnitude: 4.9Mb |
Description: This earthquake was only a few thousand kilometers away so it is not as spread out in time. The same phases are seen here, body waves and rayleigh waves, however everything is done with in less than 30 minutes. Note that the seismogram wrapped lines. like a long sentence in a book, each line is a continuation of the line above. |
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EAST COAST OF KAMCHATKA Time: 00/04/10 06:42:42 Location: 55.30N 163.12E Magnitude: 5.1 |
Description: Only the long rolling surface waves are seen in this event. The ground was very noise at the time of the recording (likely a windy storm). This conceals phases that were smaller than the noise level. From the two examples above, the body waves are often much smaller in size than the surface waves. |
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GULF OF CALIFORNIA Time: 00/04/08 18:00:59 Location: 28.40N 112.75W Magnitude: 4.1 |
Description: Magnitude 4 is very small to see for an event outside the northeastern U.S. Though is it is small notice how its rayleigh waves look like a compressed version of those seen on distant earthquakes. They are still the same seismic waves - they have just not had time to spread out and disperse. |
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MAURITIUS - REUNION REGION Time: 00/04/07 19:08:28 Location: 17.98S 65.37E Magnitude: 5.9 |
Description: Notice this event begins on the black line more than half an hour before the largest (surface) waves arrive. This is a clear indication that the quake occurred quite far away. Though these first arriving phases are small, they are significant because they are still bigger than the background noise. The surface waves continue to "ring" for an hour or more - another sign that the quake was very far away. |
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CRETE, GREECE Time: 00/04/05 04:36:57 Location: 34.22N 25.85E Magnitude: 5.4 |
Description: This event is clearly further than a few thousand miles away because it is so spread out in time. Note that there are no clearly distinguishable body waves (they arrive as sharp pulses early in the shaking). The only waves we can see here are waves which fade in a fade out. Combined with the small overall amplitude, one can conclude this event is far away and not huge. 5.4 is a respectable quake and capable of great damage in the right place, but much larger events happen regularly. |
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TALAUD ISLANDS, INDONESIA Time: 00/04/03 15:19:58 Location: 4.18N 125.61E Magnitude: 5.9 |
Description: This event shows very clear body waves (the sharp pulses of energy arriving first on the black line. These body waves are almost as large as the surface waves which arrive much later on the red line. This is often an indication that the earthquake is deep. Deep earthquakes do not generate as much energy in surface waves. Indeed, this particular earthquake occurred 120 km below the surface. This is deeper than the majority of quakes. Note the long confusing surface waves which "ring" on for nearly two hours. |
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GULF OF CALIFORNIA Time: 00/04/05 01:50:55 Location: 28.69N 112.98W Magnitude: 4.3 |
Description: Earthquakes in California are distinguishable because waves do not arrive as tightly as with events in the northeast, but they are not nearly as spread out in time as events from further away. Most of the noticeable shaking from this event is over in 5-10 minutes. Notice how the surface waves increase in amplitude and then die out rather quickly. This is a clear indication that the event is within a few thousand mile from the station. |
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NEAR COAST OF GUATEMALA Time: 00/04/01 12:49:24 Location: 13.19N 90.82W Magnitude: 4.6 |
Description: Central America produces some of the "best looking" earthquakes recorded by the LCSN. They are at just the right distance for phases to be well separated but not far enough to introduce too much complexity in the waves. This surface wave is very clear and clean looking though the event is only magnitude 4.6. There may be some faint body waves visible near the end of the prece eding red line but they are far from obvious. These surface waves clearly display a property known as dispersion. Note how the frequency of the surface waves change from low frequency (long waves) near the beginning to high frequency (short waves) near the end. This is because low frequency surface waves actually travel slightly faster than high frequency waves. This is true for most all seismograms and usually visible if one looks closely. |
| Resources | WebSeis | LCSN | http://geophysics.nmsu.edu/west/WS4instructors/gallery1.html |