ALBERT

Description: A Spanish ALERT-ES project was set up to study the feasibility of setting up an earthquake early warning system to warn of potentially damaging earthquakes that can occur in the Cape of San Vicente (SV)–Gulf of Cadiz (GC) area, located in the south west of the Iberian Peninsula, such as the 1755 Lisbon earthquake. Four events, located close to the epicenters of the largest earthquakes in the area, were simulated using different seismic software packages (Earthworm, SeisComP3, and PRobabilistic and Evolutionary early warning SysTem [PRESTo]) and the errors were analyzed. In addition, a study about the blind zone and the lead time at six selected targets was carried out. The results show a blind zone in the southwest corner of Portugal for SV earthquakes and also a blind zone in the coastal area, from Portimao to Cadiz, for the GC earthquakes.

Description: The Mw = 9.3 Sumatra earthquake of 26 December 2004 generated a tsunami that affected the entire Indian Ocean region and caused approximately 230 000 fatalities. In the response to this tragedy the German government funded the German Indonesian Tsunami Early Warning System (GITEWS) Project. The task of the GEOFON group of GFZ Potsdam was to develop and implement the seismological component. In this paper we describe the concept of the GITEWS earthquake monitoring system and report on its present status. The major challenge for earthquake monitoring within a tsunami warning system is to deliver rapid information about location, depth, size and possibly other source parameters. This is particularly true for coast lines adjacent to the potential source areas such as the Sunda trench where these parameters are required within a few minutes after the event in order to be able to warn the population before the potential tsunami hits the neighbouring coastal areas. Therefore, the key for a seismic monitoring system with short warning times adequate for Indonesia is a dense real-time seismic network across Indonesia with densifications close to the Sunda trench. A substantial number of supplementary stations in other Indian Ocean rim countries are added to strengthen the teleseismic monitoring capabilities. The installation of the new GITEWS seismic network – consisting of 31 combined broadband and strong motion stations – out of these 21 stations in Indonesia – is almost completed. The real-time data collection is using a private VSAT communication system with hubs in Jakarta and Vienna. In addition, all available seismic real-time data from the other seismic networks in Indonesia and other Indian Ocean rim countries are acquired also directly by VSAT or by Internet at the Indonesian Tsunami Warning Centre in Jakarta and the resulting "virtual" network of more than 230 stations can jointly be used for seismic data processing. The seismological processing software as part of the GITEWS tsunami control centre is an enhanced version of the widely used SeisComP software and the well established GEOFON earthquake information system operated at GFZ in Potsdam (http://geofon.gfz-potsdam.de/db/eqinfo.php). This recently developed software package (SeisComP3) is reliable, fast and can provide fully automatic earthquake location and magnitude estimates. It uses innovative visualization tools, offers the possibility for manual correction and re-calculation, flexible configuration, support for distributed processing and data and parameter exchange with external monitoring systems. SeisComP3 is not only used for tsunami warning in Indonesia but also in most other Tsunami Warning Centres in the Indian Ocean and Euro-Med regions and in many seismic services worldwide.

Description: A Spanish ALERT‐ES project was set up to study the feasibility of setting up an earthquake early warning system to warn of potentially damaging earthquakes that can occur in the Cape of San Vicente (SV)–Gulf of Cadiz (GC) area, located in the south west of the Iberian Peninsula, such as the 1755 Lisbon earthquake. Four events, located close to the epicenters of the largest earthquakes in the area, were simulated using different seismic software packages (Earthworm, SeisComP3, and PRobabilistic and Evolutionary early warning SysTem [PRESTo]) and the errors were analyzed. In addition, a study about the blind zone and the lead time at six selected targets was carried out. The results show a blind zone in the southwest corner of Portugal for SV earthquakes and also a blind zone in the coastal area, from Portimao to Cadiz, for the GC earthquakes.

Description: The increasingly dense coverage of Europe with broad-band seismic stations makes it possible to image its lithospheric structure in great detail, provided that structural information can be extracted effectively from the very large volumes of data. We develop an automated technique for the measurement of interstation phase velocities of (earthquake-excited) fundamental-mode surface waves in very broad period ranges. We then apply the technique to all available broad-band data from permanent and temporary networks across Europe. In a new implementation of the classical two-station method, Rayleigh and Love dispersion curves are determined by cross-correlation of seismograms from a pair of stations. An elaborate filtering and windowing scheme is employed to enhance the target signal and makes possible a significantly broader frequency band of the measurements, compared to previous implementations of the method. The selection of acceptable phase-velocity measurements for each event is performed in the frequency domain, based on a number of fine-tuned quality criteria including a smoothness requirement. Between 5 and 3000 single-event dispersion measurements are averaged per interstation path in order to obtain robust, broad-band dispersion curves with error estimates. In total, around 63,000 Rayleigh- and 27,500 Love-wave dispersion curves between 10 and 350 s have been determined, with standard deviations lower than 2 per cent and standard errors lower than 0.5 per cent. Comparisons of phase-velocity measurements using events at opposite backazimuths and the examination of the variance of the phase-velocity curves are parts of the quality control. With the automated procedure, large data sets can be consistently and repeatedly measured using varying selection parameters. Comparison of average interstation dispersion curves obtained with different degrees of smoothness shows that rough perturbations do not systematically bias the average dispersion measurement. They can, therefore, be treated as random but they do need to be removed in order to reduce random errors of the measurements. Using our large new data set, we construct phase-velocity maps for central and northern Europe. According to checkerboard tests, the lateral resolution in central Europe is ≤150 km. Comparison of regional surface-wave tomography with independent data on sediment thickness in North-German Basin and Polish Trough confirms the high-resolution potential of our phase-velocity measurements. At longer periods, the structure of the lithosphere and asthenosphere around the Trans-European Suture Zone (TESZ) is seen clearly. The region of the Tornquist-Teisseyre-Zone in the southeast is associated with a stronger lateral contrast in lithospheric thickness, across the TESZ compared to the region across the Sorgenfrei-Tornquist-Zone in the northwest.

Description: The GEOFON program consists of a global seismic network (GE Network), a seismological data centre (GEOFON DC) and a global earthquake monitoring system (GEOFON EQinfo). These three pillars are part of the MESI research infrastructure of the Helmholtz Centre Potsdam - GFZ German Research Centre for Geosciences aiming at facilitating scientific research. GEOFON provides real-time seismic data, access to its own and third party data from the archive facilities as well as global and rapid earthquake information. The GEOFON Seismological Software can be considered a fourth cross-cutting module of the GEOFON Program. Data, services, products and software openly distributed by GEOFON are used by hundreds of scientists and data centres worldwide. Its earthquake information service is accessed directly by tens of thousands of visitors. The SeisComP software package is the flagship software provided to the community, which is geared for seismic observatory and data centre needs and used extensively to support our internal operations. Like all other MESI (Modular Earth Science Infrastructure) modules GEOFON has the majority of users outside the GFZ as well as an external advisory committee that provides advice to the GFZ Executive Board and to the GEOFON team. This report describes the main activities carried out within the three GEOFON pillars and the software development group.

Description: ORFEUS is the non-profit foundation that coordinates and promotes digital broadband seismology in Europe. Since 1987 the ORFEUS Data Center (ODC) has been its jointly funded data center. However, within the last decade we have seen an exponential growth of high quality digital waveform data relevant for seismological and general geoscience research. In addition to the rapid expansion in number and density of broadband seismic networks this growth is fuelled by data collected from other sensor types (strong motion, short period) and deployment types (aftershock arrays, temporary field campaigns, OBS). As a consequence, ORFEUS revised its data archiving infrastructure and organization, a major component of this is the formal establishment of the European Integrated waveform Data Archives (EIDA). Within the NERIES and NERA EC projects GFZ has taken the lead in developing ArcLink as a tool to provide uniform access to distributed seismological waveform data archives. The new suite of software and services provides the technical basis of EIDA. To ensure that those developments will become sustainable, an EIDA group has been formed within ORFEUS. This founding group of EIDA nodes, formed in 2013, will be responsible for steering and maintaining the technical developments and organization of an effective operational distributed waveform data archive for seismology in Europe. The EIDA Founding nodes are: ODC/ORFEUS, GEOFON/GFZ/Germany, SED/Switzerland, RESIF/CNRSINSU/ France, INGV/Italy and BGR/Germany. These represent EIDA nodes that have committed themselves within ORFEUS to manage EIDA, that is, to maintain and develop EIDA into a stable sustainable research infrastructure. This task involves a number of challenges with regard to quality and metadata maintenance, but also to provide efficient and uncomplicated data access for users. This also includes effective global archive synchronization with developments within the International Federation of Digital Seismograph Networks (FDSN). This ORFEUS – EIDA initiative represents another step towards the construction of the European Plate Observing System (EPOS), and will be a cornerstone of the EPOS services for seismology. The EIDA infrastructure and organization will be presented with a main emphasis on on-going developments and challenges.

Description: We analyse data from seismic stations surrounding the Alboran Sea between Spain and North Africa to constrain variations of the lithosphere–asthenosphere boundary (LAB) in the region. The technique used is the receiver function technique, which uses S-to-P converted teleseismic waves at the LAB below the seismic stations. We confirm previous data suggesting a shallow (60–90 km) LAB beneath the Iberian Peninsula and we observe a similarly shallow LAB beneath the Alboran Sea where the lithosphere becomes progressively thinner towards the east. A deeper LAB (90–100 km) is observed beneath the Betics, the south of Portugal and Morocco. The structure of the LAB in the entire region does not seem to show any indication of subduction related features. We also observe good P receiver function signals from the seismic discontinuities at 410 and 660 km depth which do not indicate any upper-mantle anomaly beneath the entire region. This is in agreement with the sparse seismic activity in the mantle transition zone suggesting the presence of only weak and regionally confined anomalies.

Description: The plate boundary between Eurasia and Africa plates crosses the called "Ibero-Maghrebian" region from the San Vicente Cape (SW Portugal) to Tunisia including the South of Iberia, Alboran Sea, and northern Morocco and Algeria. In this area, the convergence, with a low rate, is accommodated over a wide and diffuse deformation zone, characterized by a significant and widespread moderate seismic activity [Buforn et al., 1995], and the occurrence of large earthquakes is separated by long time intervals. Since more than hundred years ago San Fernando Naval Observatory (ROA), in collaboration with other Institutes, has deployed different geophysical and geodetic equipment in the Southern Spain – North-western Africa area in order to study this broad deformation zone. Currently a Broad Band seismic net (Western Mediterranean, WM net) is deployed, in collaboration with other institutions, around the Gulf of Cádiz and the Alboran sea, with stations in the South of Iberia and in North Africa (at Spanish places and Morocco), together with the seismic stations a permanent geodetic GPS net is co-installed at the same sites. Also, other geophysical instruments have been installed: a Satellite Laser Ranging (SLR) station at San Fernando Observatory Headquarter, a Geomagnetic Observatory in Cádiz bay area and some meteorological stations. These networks have been recently improved with the deployment of a new submarine and on-land geophysical observatory in the Alboran island (ALBO Observatory), where a permanent GPS, a meteorological station were installed on land and a permanent submarine observatory in 50 meters depth was also deploy in last October (with a broad band seismic sensor, a 3 C accelerometer and a DPG). This work shows the present status and the future plans of these networks and some results.

Description: A Spanish ALERT-ES project was set up to study the feasibility of setting up an earthquake early warning system to warn of potentially damaging earthquakes that can occur in the Cape of San Vicente (SV)–Gulf of Cadiz (GC) area, located in the south west of the Iberian Peninsula, such as the 1755 Lisbon earthquake. Four events, located close to the epicenters of the largest earthquakes in the area, were simulated using different seismic software packages (Earthworm, SeisComP3, and PRobabilistic and Evolutionary early warning SysTem [PRESTo]) and the errors were analyzed. In addition, a study about the blind zone and the lead time at six selected targets was carried out. The results show a blind zone in the southwest corner of Portugal for SV earthquakes and also a blind zone in the coastal area, from Portimao to Cadiz, for the GC earthquakes.

Description: As part of its earthquake information service, GFZ Potsdam has started to provide seismic moment tensor solutions for significant earthquakes world-wide. The software used to compute the moment tensors is a GFZ-Potsdam in-house development, which uses the framework of the software SeisComP 3 (Hanka et al., 2010). SeisComP 3 (SC3) is a software package for seismological data acquisition, archival, quality control and analysis. SC3 is developed by GFZ Potsdam with significant contributions from its user community. The moment tensor inversion technique uses a combination of several wave types, time windows and frequency bands depending on magnitude and station distance. Wave types include body, surface and mantle waves as well as the so-called 'W-Phase' (Kanamori and Rivera, 2008). The inversion is currently performed in the time domain only. An iterative centroid search can be performed independently both horizontally and in depth. Moment tensors are currently computed in a semi-automatic fashion. This involves inversions that are performed automatically in near-real time, followed by analyst review prior to publication. The automatic results are quite often good enough to be published without further improvements, sometimes in less than 30 minutes from origin time. In those cases where a manual interaction is still required, the automatic inversion usually does a good job at pre-selecting those traces that are the most relevant for the inversion, keeping the work required for the analyst at a minimum. Our published moment tensors are generally in good agreement with those published by the Global Centroid-Moment-Tensor (GCMT) project for earthquakes above a magnitude of about Mw 5. Additionally we provide solutions for smaller earthquakes above about Mw 4 in Europe, which are normally not analyzed by the GCMT project. We find that for earthquakes above Mw 6, the most robust automatic inversions can usually be obtained using the W-Phase time window. The GFZ earthquake bulletin is located at http://geofon.gfz-potsdam.de/eqinfo For more information on the SeisComP 3 software visit http://www.seiscomp3.org http://geofon.gfz-potsdam.de/eqinfo