Rapid and reliable seismic source characterization in earthquake early warning systems: current methodologies,results, and new perspectives

In the present paper, we provided a review of the main principles and methodologies on which the current earthquake early warning systems are grounded and will also provide a perspective view for next future developments and improvements. First, we introduce the standard methodologies for the source characterization in earthquake early warning, with a special focus on the real-time earthquake magnitude determination. We discuss the suitability of existent methodologies and empirical regression laws for very large events. We then present the different approaches for the rapid prediction of the ground shaking and of the potential damaged zone, both based on traditional seismic data and on the use of continuous GPS data. Finally, the last part of the paper provides the perspective view toward a next generation of early warning systems, linking new research achievements about the earthquake rupture nucleation and the development of new methods/technologies aimed at a fast and high-resolution, real-time modeling of the ongoing source process and accurate prediction of the quake shaking at the regional and local scale.     

McGill algorithm for precipitation nowcasting by lagrangian extrapolation (MAPLE) applied to the South Korean radar network. Part II: Real-time verification for the summer season

The MAPLE system has been implemented in real-time in Korea since June 2008, producing forecasts up to 6 hours every 10 minutes. An object-oriented verification method has been applied for the summer season (June–July–August) over the Korean Peninsula to evaluate and understand the characteristics of the forecast results. The CRA (contiguous rain area) approach is used to decompose the total error into the different error components; location, pattern, and volume errors. The mean displacement error is smaller than 20 km up to the 3-h forecasts and increases with forecast time. The ratio between the displacement (location) error and the total error is less than 7% even for a 3-h forecast. This result indicates that MAPLE produces reliable forecast in terms of precipitation location. However, the pattern error is larger than 90% of the total error. Contingency scores that are defined with different categories of rain intensity and displacement errors show the outstanding performance up to 2.5 hours. MAPLE overpredicts rain areas with the threshold of 1 mm h^?1 rain intensity throughout forecast periods. However, the heavy rainfall events are poorly predicted due to the inherent limitation of extrapolation-based nowcasting technique.     

McGill algorithm for precipitation nowcasting by lagrangian extrapolation (MAPLE) applied to the South Korean radar network. Part I: Sensitivity studies of the Variational Echo Tracking (VET) technique

A Variational Echo Tracking (VET) technique has been applied to four months of archived data from the South Korean radar network in order to examine the influence of the various user-selectable parameters on the skill of the resulting 20-min to 4-h nowcasts. The latter are computed over a (512 × 512) array at 2-km resolution. After correcting the original algorithm to take into account the motion of precipitation across the boundaries of such a smaller radar network, we concluded that the set of default input parameters initially assumed is very close to the optimum combination. Decreasing to (5 sx 5) or increasing to (50 × 50) the default vector density of (25 × 25), using two or three maps for velocity determination, varying the relative weights for the constraints of conservation of reflectivity and of the smoothing of the velocity vectors, and finally the application of temporal smoothing all had only marginal effects on the skill of the forecasts. The relatively small sensitivity to significant variations of the VET default parameters is a direct consequence of the fact that the major source of the loss in forecast skill cannot be attributed to errors in the forecast motion, but to the unpredictable nature of the storm growth and decay. Changing the time interval between maps, from 20 to 10 minutes, and significantly increasing the reflectivity threshold from 15 to 30 dBZ had a more noticeable reduction on the forecast skill. Comparisons with the Eulerian “zero velocity“ forecast and with a “single“ vector forecast have also been performed in order to determine the accrued skill of the VET algorithm. Because of the extensive stratiform nature of the precipitation areas affecting the Korean peninsula, the increased skill is not as large as may have been anticipated. This can be explained by the greater extent of the precipitation systems relative to the size of the radar coverage domain.     

A cross-border regional earthquake early warning system: PRESTo@CE<Superscript>3</Superscript>RN

Since 2002 the Istituto Nazionale di Oceanografia e di Geofisica Sperimentale (OGS) in Udine (Italy), the Agencija Republike Slovenije za Okolje (ARSO) in Ljubljana (Slovenia) and the Zentralanstalt für Meteorologie und Geodynamik (ZAMG) in Vienna (Austria), are collecting, analyzing, archiving and exchanging seismic data in real time, initially in the framework of the EU Interreg IIIa Italia-Austria project “Trans-national seismological networks in the South-Eastern Alps”. As outcome of the successful cooperation, in the 2013 OGS, ARSO and ZAMG decided to officially merge their seismic monitoring efforts into the “Central and Eastern European Earthquake Research Network—CE³RN”. This work reports the results of a nine-month real-time test of the earthquake early warning (EEW) algorithm probabilistic and evolutionary early warning system carried out at the CE³RN. The study allowed identifying the actions to be implemented in order to let the CE³RN become in the next future an efficient cross-border EEW system.     

Ray tracing based on Fermat's principle in irregular grids1

A new method to trace rays in irregular grids based on Fermat's principle of minimum time is introduced. Besides the usual transmitted and reflected waves, refracted, diffracted and converted waves can also be simulated. The proposed algorithm is fast and stable, and respects the reciprocity principle between source and receiver better than procedures adopting the shooting method. It is particularly suited to form part of a traveltime inversion procedure. The use of irregular grids allows adaptation of the earth discretization to the available acquisition geometry and ray distribution, to obtain more stable and reliable tomographic images.     

Neue geologische und morphologische Untersuchungen im Tyrrhenischen Gebiet

Zusammenfassung Die 1953 im Tyrrhenischen Meer begonnenen Studien erlauben jetzt 1) ein Strukturschema des Beckens festzulegen und dieses mit den umgebenden Ländern zu verbinden.Das Gebiet teilt sich wie folgt: A: Im nördlichen Teil ein sehr unebenes paläoapenninisches Gebiet penninischen Unterbaues. B: Eine mitteltyrrhenische Tiefe (3820 m) mit einzelnen großen meist Basalt-Körpern und ein vorkalabrischer simischer Rücken mit finalorogenem Vulkankranz, in welchem hohe positive Schwereanomalien auftreten. C: Ein Gebiet von einsteigenden Hügelzügen zwischen Sizilien und Sardinien, Vorläufer des Nordafrikanischen Atlasgebietes.Es wurden lange unterseeische, auf einer tiefen tektonischen Struktur entstandene Täler und submarine Canyons entlang dem Kontinentalabfall entdeckt; besonders wo mesozoischer Kalkstein und Granite anstehen und wahrscheinlich mit Sialrandzonen zusammentreffen.Der Kontinentalschelf zeigt Spuren der würmeiszeitlichen marinen Regression, häufig auf einer viel älteren Morphologie, die aber verschieden ist von der des Kontinentalabfalles.Die pliocän und pleistocän gehobenen Brandungsspuren scheinen mit zunehmender Deutlichkeit nach Süden mit dem Gürtel mariner Vortiefen und positiver Schwereanomalien in Verbindung zu stehen.Diese Spuren verschwinden in den peripherischen Senkungszonen (Transversal-Tektonik), die dem Mittelteil der apenninischen Bögen entsprechen.     

1980 volcanic eruption reported on Marion Island

The first volcanic eruption in the recorded history of Marion Island (46°54′S, 37°45′E) occurred between February and October 1980 at a locality on the west coast. It was a minor event that passed unnoticed at the meteorological station 20 km distant. The discovery was made on November 4, by five expedition members who walked around the island. When examined in more detail on November 25, the lava was still warm in places and numerous fumaroles existed. Three blocky flows emanated from two adjacent cinder cones built-up on a pre-existing phreatomagmatic tuff cone known as Kaalkoppie. The largest flow covers an area of about seven hectares and a further two hectares have been inundated by ash. Another flow poured seawards to form a new beach front, blocking access to what was previously the largest elephant seal wallowing ground on the island. No earth tremors were felt and the activity seems to have ended for the time being.