Description: In this paper we present and discuss the performance of the procedure for earthquake location and characterization implemented in the Italian Candidate Tsunami Service Provider at the Istituto Nazionale di Geofisica e Vulcanologia (INGV) in Rome. Following the ICG/NEAMTWS guidelines, the first tsunami warning messages are based only on seismic information, i.e., epicenter location, hypocenter depth, and magnitude, which are automatically computed by the software Early-est. Early-est is a package for rapid location and seismic/tsunamigenic characterization of earthquakes. The Early-est software package operates using offline-event or continuous-real-time seismic waveform data to perform trace processing and picking, and, at a regular report interval, phase association, event detection, hypocenter location, and event characterization. Early-est also provides mb, Mwp, and Mwpd magnitude estimations. mb magnitudes are preferred for events with Mwp ≲ 5.8, while Mwpd estimations are valid for events with Mwp ≳ 7.2. In this paper we present the earthquake parameters computed by Early-est between the beginning of March 2012 and the end of December 2014 on a global scale for events with magnitude M ≥ 5.5, and we also present the detection timeline. We compare the earthquake parameters automatically computed by Early-est with the same parameters listed in reference catalogs. Such reference catalogs are manually revised/verified by scientists. The goal of this work is to test the accuracy and reliability of the fully automatic locations provided by Early-est. In our analysis, the epicenter location, hypocenter depth and magnitude parameters do not differ significantly from the values in the reference catalogs. Both mb and Mwp magnitudes show differences to the reference catalogs. We thus derived correction functions in order to minimize the differences and correct biases between our values and the ones from the reference catalogs. Correction of the Mwp distance dependency is particularly relevant, since this magnitude refers to the larger and probably tsunamigenic earthquakes. Mwp values at stations with epicentral distance Δ ≲ 30° are significantly overestimated with respect to the CMT-global solutions, whereas Mwp values at stations with epicentral distance Δ ≳ 90° are slightly underestimated. After applying such distance correction the Mwp provided by Early-est differs from CMT-global catalog values of about δ Mwp ≈ 0.0 ∓ 0.2. Early-est continuously acquires time-series data and updates the earthquake source parameters. Our analysis shows that the epicenter coordinates and the magnitude values converge within less than 10 min (5 min in the Mediterranean region) toward the stable values. Our analysis shows that we can compute Mwp magnitudes that do not display short epicentral distance dependency overestimation, and we can provide robust and reliable earthquake source parameters to compile tsunami warning messages within less than 15 min after the event origin time.

Description: The accurate estimate of the tsunami forecast is crucial in Tsunami Early Warning Systems (TEWS) framework. However, the inherent uncertainties associated with the tsunami source estimation in real-time make tsunami forecasting challenging. In this study, we consider the South American subduction zone, one of the most seismically active regions in the world, where in the last 15 years occurred, three M8+ tsunamigenic earthquakes; in particular, we focus on the 2014 Mw 8.1 Iquique event. Here, we compare the tsunami forecasting for the Chilean coast as resulting i) from the coseismic slip model obtained by geophysical data inversion and ii) from an expeditious method for the tsunami source estimation, based on an extension of the well-known spectral approach. In the former method, we estimate the slip distribution of the 2014 Iquique earthquake by jointly inverting tsunami waveforms and GPS data; on the other hand, a set of stochastic slip models in the latter is generated through a Phase Variation Method (PVM), where realizations are obtained from both the wavenumber and phase spectra of the source. We also evaluate how the different physics complexity included in the tsunami modelling (e.g. by including dispersion or not) can be mapped into the tsunami forecasting uncertainty. Finally, as an independent check, we compare the predicted deformation field from the slip models (inverted or by PVM) with the RADARSAT-2 InSAR data.

Description: The Istituto Nazionale di Geofisica e Vulcanologia (INGV) has the primary responsibility for the seismic surveillance service of the Italian territory and the tsunami alert in the Mediterranean Sea.The activities in the monitoring room at the INGV National Earthquake Observatory headquarters in Rome (hereafter INGV-Rome), are carried on by two seismologists, one tsunami specialist and one technician/engineer who work in three shifts a day to provide monitoring service on a 24/7 basis. They calculate, as rapidly and accurately as possible, the location and size of all Italian earthquakes with M2.5+ and swiftly disseminate such information to emergency authorities, to government agencies, to the public and the media by different platforms (email, text message, and via Facebook and Twitter). Starting with hypocentral and magnitude parameters, the moment tensors, the historical seismicity map and the shakemaps are also published in (near) real time. In addition, the INGV-Rome monitoring room hosts the Italian Tsunami Alert Center (CAT-INGV). CAT-INGV is one of the Tsunami Service Providers acting in the North-eastern Atlantic, the Mediterranean and connected sea (NEAM) region of the Intergovernmental Oceanographic Commission (IOC)/UNESCO and is responsible for monitoring the seismicity of the Mediterranean Sea and disseminating tsunami alert messages to member States and EU agencies subscribing its services. The operation and the performance of the INGV monitoring system is ensured by a dedicated research and IT staff who facilitate real-time waveform acquisition and distribution, develop real-time seismic processing systems and new processing algorithms.