EUROPEAN RESEARCH INFRASTRUCTURE ON SOLID EARTH

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The Near Fault Observatories (NFO) are long term research infrastructures striving to provide such multidisciplinary and high resolution near fault data and products.



 

The Near Fault Observatories (NFO) are long term research infrastructures that strive to provide multidisciplinary and high resolution near fault data and high level scientific products.
The Near Fault Observatories contributing to the NFO TCS Consortium are either operated by a single national organisation, by different national institutions, or by different national and European organisations.

 

The mission of TCS NFO is to provide coordination in between the European Near Fault Observatories, share data and products, promote best practice through the European Plate Observing System (EPOS) and encourage the road of integration in Earth Science (https://eposip.org/near-fault-observatories-europe-road-integration-why-do-we-need-nfos).

 

To achieve this the TCS NFO Consortium:

  • Defines the standard for specific data, the services and coordinates their implementation in accordance with the agreed data and products open access policy;

  • Provides access to data and derived products as defined by the NFO Consortium;

  • Shares best practice in NFO networks design and operation in terms of sensor installation, data management, software, and product development;

  • Promotes transnational access to the NFO facilities;

  • Defines and implements the information and dissemination outreach strategy;

  • Coordinates community for collaborative projects across NFOs (e.g. EPOS; ITN).

 

The NFO-TCS in EPOS consists of seven NFOs, operating on different tectonic regimes and different areas of Europe (Figure X), all at sites of elevated seismic hazard. They monitor diverse faulting mechanisms (strike-slip, normal and thrust), high to low angle faults, shallow and deep faults, as well as regions with fast (cm/yr) and slow (mm/yr) strain rate accumulation. Each fault zone can generate large earthquakes (M>6) that pose substantial to great earthquake hazard.

 

 

Three of the NFO’s operates near plate boundary systems at South Iceland Seismic Zone, the Marmara Sea and the Corinth rift. Two of the zones, Marmara Sea and Corinth, include offshore seismic sources that pose an additional tsunami hazard. The active volcanoes flanking the South Iceland Seismic zone bring the added dimension of volcano-tectonic interaction and natural geothermal activity.


The Corinth Rift Observatory - CRL
[38.15-38.5N; 21.7-22.2E]

http://crlab.eu/

Tectonic setting - The western Corinth Rift in Greece is one of the fastest continental rift in the world, with an opening rate of 1.5 cm/year, structured by a complex system of en-echelon, EW trending normal faults, rapidly evolving. It results from the southward pull of Peloponnesus due to the Aegean subduction with a possible interaction with the south-western tip of the North Anatolian fault.


 

Scientific Issues - The high level of seismic activity of the area (3 to 4 earthquakes of magnitude 6 to 6.6 per century since 1700; the more than 30,000 well recorded events with M>1.5 since 2001 and the fast strain rate of 10-6/yr inferred from GPS allows to tackle many fundamental aspects of the mechanical processes on seismogenic faults, as well as hazard issues [13]. At the crustal scale, the relative importance of a creeping north-dipping detachment and a possible mode-I, axial strain source beneath the microseismic layer remains debated. At the fault scale, the rooting, interaction mode, and connectivity at depth of the major faults have to be better constrained and modelled. At the microseismicity level, the most active volume is a depths. The swarm-like and diffusive nature of the micro-seismicity strongly suggests a critical role of pore pressure migration, and the presence of high pore pressure whose source remain to be discovered. Locating, quantifying, and modelling the seismic and aseismic, multiscale, coupled processes are a key for a reliable probabilistic short- and medium- term earthquake forecast. Integrating geological, seismological, geodetic geodetic, and historical data and models into a logic-tree methodology led to a probability range.

   


Marmara Sea GEO Supersite - EU MARSite
[39.0-42.0N; 26.0-31.0E]

Tectonic setting - The North Anatolian fault (NAF) is a major right lateral, strike-slip fault extending for 1200 km from eastern Turkey to the north Aegean Sea. It accommodates the relative motion between the Anatolian region and Eurasia at a rate of ~ 25 mm/yr [29, 30]. Along its westernmost segment the fault bifurcates into a north and a south branch. The northern branch follows the Izmit Bay and enters the Sea of Marmara SE of Istanbul. By far the majority of long-term fault slip occurs on the segment following the NW-striking Princes’ Island fault (PIF) and joining the EW-striking Central Marmara fault (CMF) immediately south of Istanbul. After traversing much of the Sea of Marmara, the CMF merges with the Ganos fault, exiting the Sea along the Ganos Peninsula.

The Marmara segments are located close to the mega-city of Istanbul (13 million of people consisting of the 18% of the country’s population), the cultural and, financial heart of Turkey.

Scientific Issues - During the past century, a series of predominantly westward migrating M>7 earthquakes broke an ~1000 km section of the NAF. Currently, basing on long-term (>20 years) GPS observations, historical and instrumental seismological data, the major seismic gap is located under the Sea of Marmara (Main Marmara fault; MMF). Direct observations of strain accumulation on the Princes’ Islands segment of the MMF [36] constrain a slip deficit rate to 10–15 mm/yr. In contrast, the central segment of the MMF shows no evidence of strain accumulation, suggesting that fault creep accommodates fault motion.
Furthermore, the PIF is most likely to generate the next M>7 earthquake along the Marmara Sea segment. These outcomes provide a basis for focused studies on fault creep generation/behavior, the relationship between creeping and seismic activity, the role of fault creep on the earthquake cycle and for stress transfer.

Thus, in 2012 the MARSite project was initiated under the EC/FP-7 framework as an initiative towards establishment of new directions in seismic hazard assessment through focused earth observation in Marmara Region. As a consequence this region hosts the largest near-fault infrastructure in Europe.

Observatory Overview
MARSite is a multidisciplinary network whose backbone is composed by seismic and geodetic stations. Seismic stations equipped with both broad-band (BB) and strong motion sensors are located at the surface and within boreholes, on land and in the Marmara Sea. Geochemical stations, also, run to support this backbone. Systematically, geophysical surveys (micro-gravity, resistivity etc.) are organized to increase the spatial sampling. As an underwater acoustic experiment, autonomous acoustic ranging transponders have been deployed to determine whether or not the plate interface is (fully or partially) locked, to calculate the rate of aseismic creeping, capture eventual temporal fluctuations, and to determine the frictional fault properties.

 


The South Iceland Seismic Zone Observatory
[63.75N - 64.25N; 21.5W – 19.5W]

Tectonic setting - The South Iceland Seismic Zone (SISZ) is an 80-km-long, 20 km wide E-W trending sinistral shear zone, offseting the two rift zones in southern Iceland where spreading is 19 mm/yr. [17,18]. Faulting in the SISZ occurs on N-S, subparallel faults, with right-lateral slip exhibiting a pattern of book-shelf faulting. Sequences of several major destructive events, up to M7.1, sweep across the zone every century, exhibiting dynamic triggering of events up to magnitude M5.5. Volcano-tectonic interaction is observed between the SISZ and neighbouring volcanoes, Hekla and Hengill. Induced seismicity, with up to M4 earthquakes is observed at the intersection of the SISZ with the western volcanic zone (WVZ).

Scientific Issues - Iceland is one of the few places on Earth where mid-ocean rifting can be observed on land, with accompanying high seismicity rate, moderate- to large-magnitude earthquakes and volcanism. The focus of the work in the SISZ has been on mapping the book-shelf fault matrix with high precision locations and analyzing their slip and surface deformation with high-density and high-rate GPS observations and modeling. The fault traces of most of the historical earthquakes in the SISZ have already been mapped on the surface and in the subsurface with the abundant microseismicity; 2-20 thousand earthquakes/year. Unique observations of dynamic triggering of M>5 earthquakes at up to 70 km distance were made in June 2000. Less than half of the accumulated shear stress has been released by the three recent M>6 events and earthquake hazard remains high, especially in the eastern part of the SISZ. The repeated faulting gives rise to low-temperature geothermal activity, which is utilized for municipal heating. At the intersection of the SISZ with the WVZ, active high-temperature geothermal activity is also observed and utilized. The volcano-tectonic interaction between unrest/uplift at Hengill volcano and seismic activity in the SISZ (over 90 thousand earthquakes in 6 years) has been mapped and currently analysed.

Observatory Overview
The multidisciplinary network in the SISZ consists of seismic, GPS and volumetric borehole strain meters. The seismic network includes short-period, broadband and strong motion stations. Many of the GPS stations are high-rate and some are co-located with seismic stations. The present strain meter network is concentrated in the eastern part of the SISZ where it monitors magma movements at Hekla volcano. Numerous boreholes exist in and around the SISZ and water level and chemistry is monitored in some.

 

In mountain settings, NFOs monitor the Alto Tiberina and Irpinia faults in the Appennine mountain range, the Valais region in the Alps, and the Vrancea fault in the Carpathian Mountains. Steep slopes and sediment-filled valleys in the Valais give rise to hazards from landslides and liquefaction.

 


The Irpinia Observatory
[40.0- 41.25N; 14.0-16.2E]

Tectonic setting - The Irpinia Fault system is a series of subparallel and antithetic normal faults, three of them responsible for the 1980, M 6.9, Irpinia Earthquake. The fault system is located in the Southern Apennines of Italy, along a sector of the chain undergoing an extension rate of 2-3 mm/yr.

Scientific Issue - INFO is aimed to investigate the details of faulting processes associated with the background seismicity and the preparation phase of large earthquakes in the region through the fine characterization and modeling of microseismicity and other transients on the faults. It is also devoted to issue an early warning during the occurrence of a significant event in the area, through continuous, real-time data transmission and processing. Investigation of the background seismicity is mainly concentrated on the study of the seismic sequences occurring at the base of the faults that generated the 1980 earthquake, in terms of space-time-magnitude statistical properties and source parameters, to understand the role of the fluids in the generation and evolution of the microseismic activity of the area.
Through accurate modelling of and attenuation tomographies are aimed to track the changes in the medium with time.

Observatory Overview
INFO is mainly based on the seismic network ISNet (Irpinia Seismic Network) managed by AMRA scarl. The network consists of 32 stations organized in sub-nets that are connected with real-time communications to a central data-collector site. To ensure a high dynamic recording range, most of the seismic stations are equipped with a strong-motion accelerometer with large full scale (1g) and a three-component velocitymeter (broadband or short period) or accelerometer with small full scale (0.25g). Data are real-time sent to Naples University with a controlled delay time.


The Altotiberina Observatory

Tectonic setting - The Alto Tiberina fault (ATF) is one of the rare worldwide examples of an active low angle (NE-dipping at 15°) normal fault (LANF). This NW-trending fault is located in the Northern Apennines of Italy, along a sector of the chain undergoing a NE-trending extension rate of 2-3 mm/yr.

Scientific Issues - The possibility that moderate-to-large earthquakes nucleate on low-angle normal faults (LANF, i.e., normal faults dipping less than 30°), accommodating extension of continental crust, is widely debated in the published literature. Anderson-Byerlee frictional fault mechanics predict no slip on normal faults dipping less than 30° in an extensional tectonic setting characterized by a vertical σ1, if faults have a friction coefficient (μs) ranging between 0.6 and 0.85. This should mean that mechanically it is easier to form a new fault instead of reactivating a severely misoriented low-angle structure. This hypothesis is supported by the observation that no moderate-to-large earthquake ruptures have been documented on LANF using positively discriminated focal mechanisms. Therefore, LANF are believed to be unimportant structures in terms of seismic hazard. The Observatory Overview paragraph is missing. They all need to be homogenous descriptions. The same for the Figures. Below what I have stolen from the past EGU poster. Therefore, TABOO has been built by the INGV to study the seismic and aseismic deformation processes active along this 50 km long structure that has accumulated 2 km of displacement over the past 2 Ma, in a densely populated area.

Observatory Overview
TABOO is a multidisciplinary network whose backbone is composed by seismic and geodetic stations. The seismic stations equipped with both short period and strong motion sensors are located at the surface and within shallow boreholes. The GPS antennas and the corner reflectors are co-located with the seismic stations for both increasing the observation parameters spectra and decreasing the installation costs. New Radon and geochemical stations complement such a backbone.


The Valais Observatory
[46.0- 46.5N; 7.0-8.2E]

Tectonic setting - The region of Valais has the highest seismic hazard in Switzerland, experiencing a magnitude 6 or larger earthquake every 100 years. Although the time occurrence of strong earthquakes in the area was regular in past centuries, the instrumental seismicity of last decades presents a peculiar spatial pattern. We observe a high seismic activity in the region of the 1946 MW=5.8 earthquake, whereas a seismic quiescence in the area of 1755 MW=5.7 and 1855 MW=6.2 events. Differen- ces in seismicity between northern and southern Valais manifest themselves both by the style of faulting and changes in the stress field orientation. In addition to high seismic activity, the Valais has several factors adding to the total hazard level: rough topography with unstable and steep slopes, deep sediment-filled valleys, and wide glacier- and snow-covered areas. The area has experienced significant damage and induced effects from strong ground motion during previous large earthquakes, which also included secondary phenomena such as liquefaction in the Rhone plain, deep-seated landslides, and extensive rockfalls. A major goal for the Valais is interdisciplinary investigation of short- and long-term earthquake preparation processes, in addition to complex surface effects induced by strong ground motion. The seismic network in the Valais is operated by the Swiss Seismological Service (SED).

Scientific Targets

  • Investigate the physics of small earthquakes and its relation with large events;
  • Understanding of observed ground motions (source-path-site).
  • Identification of active faults.
  • Seismicity pattern.
  • Precursory phenomena.
  • Earthquake secondary phenomena (landslides, liquefaction).
  • Linking historical and recent observations.
  • Seismic hazard and risk scenarios.

Observatory Overview
The multidisciplinary observation system with a backbone of:

  • Seismic network (SED, ETHZ): 19 modern strong motion, 10 broadband, 4 short period.
  • 1 geochemical station; 1 magnetic station (SED, ETHZ).
  • 11 GPS (swisstopo, GGL, ETHZ)

All of the instruments send real time data to the acquisition centres. A strong motion borehole array is being installed in summer 2015.


The Vrancea Observatory
[44.9- 46.0N; 24.32-28.04E]

Tectonic setting - The Vrancea area within the bend region of the Carpathian orogen is one of the most active seismic zones with intermediate depth earthquakes in Europe. These earthquakes often exceeding Mw 7.0 are felt on a wide area. This is also the only NFO operating in a region undergoing tectonic compression.

Scientific Issue - The Vrancea seismogenic zone in Romania represents a peculiar source of seismic hazard, which is a major concern in Europe, especially to neighbouring regions of Bulgaria, Serbia and Republic of Moldavia. Earthquakes in the Carpathian - Pannonian region are confined to the crust, except the Vrancea zone, where earthquakes with focal depth down to 200 km occur. One of the cities most affected by earthquakes in Europe is Bucharest where were encountered many damages due to high energy Vrancea intermediate-depth earthquakes; the March 4, 1977 event (MW =7.2) produced the collapse of 36 buildings with 8-12 levels, while more than 150 old buildings were seriously damaged. Therefore, National Institute for Earth Physics (NIEP) has built the Vrancea Observatory in Romania to develop new multidisciplinary approaches and methodologies to earthquake science.

Observatory Overview
The Vrancea Observatory is a multidisciplinary network whose backbone is composed by seismic stations together with infrasound and seismic arrays, a GPS network, a Radon monitoring system, meteorological stations, electromagnetic stations and atmospheric ionization monitoring systems. The seismic stations are equipped with both short period/broadband and strong motion sensors are located at the surface and within shallow boreholes.

 

WP09 Leader: Lauro Chiaraluce

WP09 Communication Contact Person: Dragos Tataru