Re: anyone, what does the "?" mean??
Posted by
Chris in Tampa on 3/12/2011, 1:31 am
"Magnitude = ? for new earthquakes until a magnitude is determined (takes 4-5 minutes)." (from the tips section)
The quake does appear but it can be a little confusing for some of the smaller quakes. (especially in regards to one appearing and then disappearing)
It does appear here:
http://earthquake.usgs.gov/earthquakes/recenteqsus/Maps/US10/37.47.-125.-115_eqs.php
MAG UTC DATE-TIME LAT LON DEPTH (km) LOCATION
1.8 2011/03/12 04:41:39 38.832 -122.793 2.7 4 km ( 2 mi) NNE of The Geysers, CA
But it does not appear here:
http://earthquake.usgs.gov/earthquakes/recenteqsww/Maps/10/240_40_eqs.php
The reason is because in the left column under "Present" you can go to "Real-time - Worldwide" for quakes worldwide which shows all quakes 2.5 or greater in the US and all quakes 4.5 or greater for the rest of the world. If you go to the "Real-time - USA" or more narrowly "Real-time - CA/NV", then you are actually going to get all quakes 1.0 or greater. The USGS just doesn't display smaller quakes from around the world. Being a US agency though, they do show the tiny ones in the US though. (It's not that the US just has smaller quakes more, it's just the USGS doesn't show those in other places in the world, meaning while there are significant aftershocks from the Japan earthquake, there are a lot more smaller earthquakes that the USGS is not showing.)
The worldwide tab shows US quakes 2.5 or greater and the US tab US quakes 1.0 or greater. What might have happened is that the quake magnitude was unknown and put on the worldwide page briefly and when the magnitude was estimated to be under 2.5 it was removed and at that point only appeared on the US tab where all 1.0 or higher quakes are shown. |
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anyone, what does the "?" mean?? -
hillsboroughweather,
3/11/2011, 11:48 pm Post A Reply
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