Monday, 7 January 2008

Did the earth move for you, too, dahl-ing?

Oh-er! I woke up in a bit of a panic just before midnight to the sound of crashing from the dock and the boat being shaken as if by a giant hand. Was it a dream, had we hit a reef....

No! TBH rolled out of bed and announced that it was an earth tremor (of course he has been in them before!). A quick look around outside, one or two other boaters appeared from hatches like startled gophers, and seeing that the docks were still in place it was back to bed.

We had a small shake when in Trinidad but nothing as strong as this. I found an interesting website on which you can report the tremors you feel and they draw a map and try and classify the event. Turns out there have been two tremors already this week in Guatemala, to the south west of here centred on the Pacific Coast.
This map shows the report of the tremor that occurred on 5th January, there was another reported on 6th January.
There is some fascinating stuff on the site about the phenomena. This bit particularly interested me as I though the motion we experienced was pretty strong, not at all like a rolling motion.

The actual time it takes for a fault to slip depends on the size of the earthquake. A magnitude 5 earthquake slips for about a second; a M6 for a few seconds; a M7 for several seconds. The duration of shaking you actually feel from an earthquake depends in part on the distance you are from the epicenter of the earthquake. If you are close, the shaking will be more violent, "faster", and may not last as long. If you are further away, the high-frequency "fast" shaking will have been "absorbed" into the earth's crust, you will feel are the longer-period, more rolling motions, and they may be of longer duration. In short, the duration is different in different places, even for the same earthquake. In addition, observers in the nearby locations may describe different directions depending on the type of building they are in, and how each perceives the shaking.

Magnitude 4.2
  • Monday, January 07, 2008 at 05:51:50 UTC
  • Sunday, January 06, 2008 at 11:51:50 PM at epicenter
Time of Earthquake in other Time Zones
Location 15.599°N, 88.910°W
Depth 10 km (6.2 miles) set by location program
Distances 40 km (25 miles) WSW of Puerto Barrios, Guatemala
95 km (60 miles) W of San Pedro Sula, Honduras
205 km (125 miles) ENE of GUATEMALA CITY, Guatemala
1170 km (720 miles) ESE of MEXICO CITY, D.F., Mexico
Location Uncertainty horizontal +/- 15.1 km (9.4 miles); depth fixed by location program
Parameters Nst= 24, Nph= 24, Dmin=245 km, Rmss=0.82 sec, Gp=191°,
M-type=body magnitude (Mb), Version=Q
Event ID us2008lxag

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