located events to invert for a new 1D minimum velocity model for both
P- and S-waves using VELEST. A depth region of a lower vpvs ratio down to 20 km depth is revealed.
We perform relocation of the whole dataset using the new velocity model and the double-difference
relocation technique. We look into details of the depth distribution of the events and how the relocation
procedure affects
/media/norsem/norsem_buhcheva.pdf
shows the direction of the wind, which blows toward the point of the barb. Wind-speed is symbolized by diagonal lines at the end of the barb; for instance, a short line represents 2.5 m/s, a long line 5 m/s and a triangle represents 25 m/s.
Mean sea level pressure is shown in solid lines, the contour interval is 2 hPa.
The sliding bar below the map is used to change the validity time
/weather/articles/nr/1211
than can be expected to originate from the cauldrons, three to four times the wa-
ter equivalent of the accumulation of snow over the watershed of the cauldrons. It has
been estimated that flow from the cauldrons, in addition to the jökulhlaups, could be
2–5 m3 s 1 at maximum (Vatnaskil, 2005). It is possible that part of the sulfate-rich
groundwater from the glacier comes from the cauldrons
/media/vedurstofan/utgafa/skyrslur/2009/VI_2009_006_tt.pdf
located, has now been relocated using a double-difference relocation method. This approach provides a much sharper image of the event distribution.
The same technique has been used to map fault planes widely in Iceland, as well as magma pathways in volcanoes, such as Eyjafjallajökull (pdf 3,1 Mb).
The map (click to enlarge) shows earthquakes beneath Eyjafjallajökull between March 13th and 24th
/about-imo/news/nr/1859
and
calculated travel time differences for pairs of closely spaced earthquakes observed at a series of
recording stations. Each earthquake is paired with several other earthquakes and the best fitting
distances between them as a group are determined. Methods based on this kind of minimization are
called double-difference (DD) earthquake location algorithms
/media/norsem/norsem_begga.pdf
Iceland Seismic Zone. It was implemented in connection with the European REAKT project and lead
by Kristin Vogfjörð. We use cross-correlation and double difference methods from Ragnar Slunga. We
correlate new single automatic located events with waveforms of events from a high-resolution library
(catalog) of active mapped faults in the area and also from a library of well located single events
/media/norsem/norsem_gunnar.pdf
have started applying double-difference method of Waldhauser and Ellsworth
(2000), to improve earthquake location accuracy in the area.
On spatial resolution scale on the order of the size of the Southern Iceland Lowland (~70 km), we have
been able to measure velocity ratios at ~0.04–0.1% significance (1 σ) with the uncorrected SIL catalog
data. Preliminary results can be interpreted
/media/norsem/norsem_ingi.pdf
J-17, J-21 and M-29. Locations of seismic stations are also sown
(purple triangles).
High-precision earthquake locations, with optimum achievable location accuracy on the order
of tens of meters are currently obtained through relative relocation (double difference) of
manually located earthquakes (Slunga et al., 1995; Hjaltadóttir and Vogfjörd, 2005). The
objective is to obtain
/media/vedurstofan/utgafa/skyrslur/2010/2010_012rs.pdf
There is a double pulse cycle, or fluctuation, one takes hours and the other
takes between 10 and 20 seconds.
Seismic activity in Bardarbunga continues to be strong. The biggest earthquakes that was detected since noon on
Friday, were of magnitude M5,1 on Sunday, 23. November at 09:22 and this morning, 24. November, at 09:03 of
magnitude M5,4. In total 36 earthquakes bigger then M4,0 were
/media/jar/Factsheet_Bardarbunga_20141124.pdf