Present day in-situ monitoring networks of volcanic and seismic hazards

A description (19 March 2013) of in-situ monitoring networks in Iceland and available results.

Compiled by: Freysteinn Sigmundsson (fs@hi.is), Kristín Vogfjörð (vogfjord@vedur.is), Benedikt G. Ófeigsson (bgo@vedur.is), Sigrún Hreinsdóttir (runa@hi.is), Matthew J. Roberts (matthew@vedur.is), Maurizio Ripepe (maurizio.ripepe@unifi.it), Magnús T. Guðmundsson (mtg@hi.is) and other members of the FUTUREVOLC team.

The Icelandic Meteorological Office (IMO) leads long-term monitoring of geohazards in Iceland and is responsible for maintaining instrument networks for this purpose.

IMO has extensive collaboration with a number of Icelandic and international research groups, including the Institute of Earth Sciences (IES), University of Iceland.

In-situ instrumentation to monitor geological hazards in Iceland includes seismic, GPS, strain, hydrological, radar, infrasound networks, and scanning DOAS spectrometers.

IMO is Iceland’s leading partner in the EPOS project (PI for Iceland is Kristín Vogfjörð). Permanent networks included in EPOS are described in the EPOS RIDE data base (Research Infrastructure Metadata base for EPOS):

Selecting a country filter and Iceland gives an overview of the in-situ networks described in EPOS RIDE. Information on the networks is found by selecting the relevant network (the GPS network is divided into 3 parts).

Seismic results

The national seismic network is named the SIL network. Present seismic stations are shown as green dots on Figure 1.1. This network has been operated by the IMO since 1990s, initiated from a Nordic project covering the South Iceland Seismic Zone in the 1990s but has expanded to cover all of Iceland. This network is complemented with various temporary and permanent seismic installations in Iceland, e.g. by IES, University of Uppsala, Sweden, University of Cambridge, UK, and British Geological Survey (BGS). Data from stations from temporary networks are in some cases transmitted directly in real time to IMO and included in near real-time analysis.

A map of the seismic SIL stations

Processed results from the SIL network are available from IMO in various forms – some with description in Icelandic.

Link containing the automatic locations from the SIL network for the last 48 hours – NOT manually checked.
(kort = map, tafla = list of earthquakes): 

Summary of weekly activity – revised earthquake locations

A folder holds information for each year (e.g. folder 2013 holds information regarding seismicity in 2013.). Subfolder for each week (Icelandic vika) shows maps for activity each week, based on list of earthquakes that have been manually checked.

Naming convention is the following:  yyyy is a year and ww is the number of week in that year.

Alert maps and shake maps
There are two links:
Alert maps:
Reveals a list of earthquakes. By clicking on items in the list three maps for each event are shown. From left: time of peak ground velocity (PGV), amplitude of PGV, and onset time of
P-wave arrival.

Shake Maps:
Reveals a list of shake maps. They are drawn with the USGS ShakeMap software receiving PGV and peak ground acceleration information for the SIL stations, and using PGV and PGA attenuation relations as well as Intensity (PGV, PGA) derived for seismic wave propagation in Iceland.

Continuous GPS results

The present stations of the national GPS network (ISGPS) are shown as red triangles on Figure 1. The build-up of continuous GPS monitoring in Iceland has been accomplished by various international collaborative projects. Eventually the build up of these “sub-networks”  has formed a network of close to 80 stations distributed along the volcanically and seismically active zones in Iceland. Several universities and institutions, with the support of research funds, have contributed to the build up of the network. Among the main contributors are University of Iceland, University of Arizona, Penn State University, Savoie Universiy in France, ETH in Zürich and King Abdulla University, KAUST, in Saudi Arabia and Bavarian Academy of Sciences and Humanities, Germany. Power companies Landsvirkjun, Orkuveita Reykjavikur and HS Orka, as well as the National Land survey of Iceland have also contributed.

There are two IGS (International Geodetic Service) GPS stations in Iceland, Hofn (HOFN) and Reykjavik (REYK).

Data from these stations are analyzed by many international agencies and are included in the global ITRF velocity field.

Data from the many international collaborative GPS-monitoring projects in Iceland are analyzed by various agencies. Results from daily analysis of all continuous GPS sites in Iceland are available at IES and IMO. 

Sigrún Hreinsdóttir at IES maintains a site with updated detrended time series from all stations.

This sites includes a description of the data and time series. The detrended time series are particularly useful to check for deviations of displacement patterns from previous trends, such as due to magma movements in volcanoes.

IMO (contact person Benedikt G. Ófeigsson) present raw time series (not detrended) in the ITRF2008 reference frame.

The site (under construction) includes also station map as well as some background information. The time series also reveal anomalous displacement patterns, but background velocities in ITRF2008 reference frame have to be considered as well as annual cycles in derived movements.

Strain results

A network of borehole strainmeters (Sacks-Evertson borehole dilatometers) is operated by IMO (contact person Matthew J. Roberts) in collaboration with the Carnegie Institution of Washington (CIW). Data streams (uncorrected) from four strainmeters.

These have proven successful to detect immediate precursory signals to eruptions of the Hekla volcano. A real-time monitoring of strain and seismicity at Hekla.

Infrasound result

On active volcanoes, volumetric sources rapidly expanding in the atmosphere produce infrasound providing valuable insights into eruption dynamics and into the state of volcanic activity in general.

Explosive activity in Iceland is monitored by a 4-element infrasonic array with a triangular geometry and an aperture (maximum distance between two elements) of ~120 m. The array is operating in Gunnarsholt South Iceland and each element is equipped with differential pressure transducer with a sensitivity of 25 mV/Pa in the frequency band 0.001-50 Hz and a noise level of 10-2 Pa. Infrasound is recorded on site at 100 Hz and 24 bits and transmitted via Internet link both to the Icelandic Meteorological Office (IMO) and the Department of Earth Science of University of Florenze, Italy (UNIFI).

Location of the infrasonic source is performed by array multi-channel semblance analysis applied on a grid-searching procedure to identify in real-time signals from noise in terms of propagation back-azimuth and apparent velocity. Data and source location.

Infrasonic monitoring allows for real-time determination of parameters such as onset, duration and intensity of the eruption. Data collected during the Eyjafjallajökull 2010 eruption indicate that infrasound could be used to calculate mass eruption rate and plume height in real-time

Contact person is Maurizio Ripepe (UNIFI).

Real-time hydrological data

Many of the volcanoes in Iceland are glacially covered. For these, the monitoring of the rivers emanating from the overlying ice caps is of particular importance.  IMO runs a country-wide network of sensors for river flow.

Contact person is Matthew J. Roberts at IMO


In case of unrest:

In case of eruptions, daily situation reports will be (as they have been in the past) prepared jointly by IMO and IES, outlining the situation, explaining signals observed with the in-situ monitoring networks and other available information.

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