9:00AM Wednesday 31 December 2003
Investigations instigated by the Lieutenant-Governor of Saba Mr. Antoine Solagnier have identified the source of the seismic events recorded over the past ten days. The main pier of the harbour in Saba was damaged by hurricane Lenny in 1999 and is now being demolished in preparation for replacement. It is being demolished by a crane which hoists a ten-tonne mass to a height of approximately 25 meters and then drops the weight onto the pier. The demolition site is about one kilometer horizontally and 320 meter vertically from our seismograph station and the energy generated bythe impcts is entirely sufficient to explain the observed signals.
Update 5 PM Tuesday 30 December 2003
The seismic events in Saba have continued at a rate of about one every five minutes throughout the afternoon. The events are spaced extremely regularly, and occur only during daylight hours which suggests an artificial origin but investigations in Saba have not yet identified a possible cause.
Update 12 Noon Tuesday December 30
The sequence of seismic events in the island of Saba which began last week and continued to December 28 was renewed briefly today, December 30, when seven (7) events occurred in rapid succession between 10:43 AM and 11:00 AM Local Time. Saba is the smallest island under separate administration in the eastern Caribbean and essentially consists of the single volcano Mt. Scenery. Pictures and descriptions of Mt. Scenery can be found on the Documents section of this site.
The most recent severe earthquake swarm near Saba occurred in 1992 (Ambeh and Lynch, Tectonophysics 246 (1995) 225-243. These authors considered that the 1992 events had a tectonic rather than volcanic origin. The ongoing events are much smaller than those of 1992 and the most likely explanation at the moment is that they are of artificial origin.
No descriptions of volcanic eruptions in Saba have been found in the literature written since Europeans first began to settle there in 1640 AD. This is slightly puzzling because the youngest pyroclastic flow deposits in the island contain fragments of European pottery, and a radiocarbon date for these deposits suggests that they were erupted in 1670 AD (+/- 60 years). Other radiocarbon dates for different deposits are 1425 AD (+/- 60 years), 3,155 +/- 65 years and 34,750 (+/-850 ) before present. The more recent eruptions occurred while the island was occupied by Amerindians and the most recent may have been since European settlement. Further literature searches may yet yield descriptions of this event (or events).
28 December 2003
Over the Christmas period and continuing to Sunday December 28 our seismograph station in Saba recorded a very large number of small seismic events. At the moment we are uncertain whether these are genuine earthquakes or whether the signals are generated by some other activity such as onshore or offshore explosions. All that we know is that the signals are being generated on or close to the island of Saba, in the Netherlands Antilles. If anyone can cast any light on these phenomena please e-mail us at uwiseismic@uwiseismic.com.
