Jökull - 01.01.2017, Side 10

Microearthquakes on the eastern flank of Katla volcano, S-Iceland
Figure 2. The seismic network and seismicity at Katla between May 2011 and August 2013 (Jeddi et al., 2016).
Dark triangles: permanent IMO seismic stations. Orange triangles: temporary UU and RU seismic stations op-
erating between May 2011 and August 2013. Red dots: earthquakes located in the 3-D velocity model by Jeddi
et al. (2016). The eastern seismic activity is outlined with a black rectangle. Topography information from the
National Land Survey of Iceland. – Jarðskjálftamælanet í nágrenni Kötlu frá maí 2011 til ágúst 2013 (eftir
Jeddi og fl., 2016). Svartir þríhyrningar: varanlegir mælar Veðurstofu Íslands; Appelsínugulir þríhyrningar:
tímabundnir mælar Uppsalaháskóla og Háskólans í Reykjavík reknir frá maí 2011 til ágúst 2013; Rauðir punkt-
ar: jarðskjálftar staðsettir í þrívíddarlíkani (eftir Jeddi og fl., 2016). Virka svæðið austan í Kötlu er afmarkað
með svörtum ferhyrningi. Landhæðarupplýsingar frá Landmælingum Íslands.
2. The vast majority of the events belonging to fam-
ily 1 occurred between December 4th and 12th, 2011,
with their correlation coefficient (R) ranging between
0.6 and 0.99 (40 events with R>0.8). Most of the
events in family 2 occurred on December 4th and 5th,
2011, and their correlation coefficients were higher
than 0.88. The correlation coefficient between the ref-
erence events of the two families was ∼0.35.
In order to look for seismic activity in the same
area prior to the installation of the temporary stations,
we searched for eastern events in the IMO catalog
from the beginning of the monitoring to the end of
2013 (because continuous data are not available for
the whole period). We found 34 events with the first
one registered in November 2001.
Figure 4a shows the cumulative number of eastern
events in the IMO catalog between 2001 and 2013. A
remarkable feature is the sharp increase at the end of
2010 (mostly in November, before the installation of
our temporary network) by 41% of all eastern events
in the IMO catalog. Figure 4b shows the time period
between June 2011 and August 2013 when the tempo-
rary stations were added to the network. We show the
cumulative number of events detected with correla-
tion at the KKE and LOD stations in this time period.
Small increases in July and September are followed
by a big increase in December 2011. A small increase
occurs also in June 2012.
Observations from the IMO catalog together with
the cross-correlation results show a swarm-like be-
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