Advancing the Frontiers of Earthquake Science

Statistical seismology has been emerging as a new discipline at the interface between earthquake physics, earthquake statistics, hazard assessment, and society. A workshop in Italy was sponsored by the Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV), the Swiss Federal Institute of Technology Zurich (ETH), and the Japanese Institute of Statistical Mathematics (ISM), to discuss the state of the art and future directions. Conference participants discussed how to use available tools and techniques of statistical seismology to advance earthquake science. Building increasingly accurate timedependent earthquake forecast models at various spatial and temporal scales is widely recognized as an important challenge, and various such models were presented and discussed at the workshop. Exploiting time dependence for hazard assessment requires us to develop a detailed understanding of the behavior of regional fault systems and corresponding earthquake catalogs spanning decades. We can no longer analyze individual faults or earthquake sequences in isolation

Improving seimic hazard assessment in the Mediterranean Region

This paper is intended as a short presentation of the main limitations affecting seismic hazard assessment, revisiting possible methods available in the literature to be applied for this purpose. The convergence of the African Plate with the Eurasian Plate is the cause of the high seismic activity characterizing the Mediterranean region, with particular intensity in its eastern part. It is clear that the associated seismic risk requires appropriate measures for its mitigation. Seismic risk, the amount of resources that the community is expected to pay to earthquakes in the long term, is the product of three factors, such as seismic hazard, vulnerability and value of the exposed goods. As earthquakes cannot be prevented, seismic risk can be mitigated by improving our knowledge of seismic hazard, which is largely based on statistical analysis of historical earthquake catalogs. Nevertheless, historical records are affected by problems of reliability, completeness and shortness, as they commonly span time lengths of the same order of magnitude or even shorter than the inter-event time of the strongest earthquakes produced by specific seismic sources. In this respect, alternative methods can be proposed for integrating and improving our knowledge of seismogenic processes, and estimating both time-independent and time-dependent occurrence rates of strong earthquakes. We propose the application of physics-based earthquake simulators, requiring the knowledge of a robust geological-geophysical seismogenic model

Earthquake location in tectonic structures of the Alpine Chain: the case of the Constance Lake (Central Europe) seismic sequence

AbstractA set of four magnitude Ml ≥ 3.0 earthquakes including the magnitude Ml = 3.7 mainshock of the seismic sequence hitting the Lake Constance, Southern Germany, area in July–August 2019 was studied by means of bulletin and waveform data collected from 86 seismic stations of the Central Europe-Alpine region. The first single-event locations obtained using a uniform 1-D velocity model, and both fixed and free depths, showed residuals of the order of up ± 2.0 s, systematically affecting stations located in different areas of the study region. Namely, German stations to the northeast of the epicenters and French stations to the west exhibit negative residuals, while Italian stations located to the southeast are characterized by similarly large positive residuals. As a consequence, the epicentral coordinates were affected by a significant bias of the order of 4–5 km to the NNE. The locations were repeated applying a method that uses different velocity models for three groups of stations situated in different geological environments, obtaining more accurate locations. Moreover, the application of two methods of relative locations and joint hypocentral determination, without improving the absolute location of the master event, has shown that the sources of the four considered events are separated by distances of the order of one km both in horizontal coordinates and in depths. A particular attention has been paid to the geographical positions of the seismic stations used in the locations and their relationship with the known crustal features, such as the Moho depth and velocity anomalies in the studied region. Significant correlations between the observed travel time residuals and the crustal structure were obtained

Automatic inspection and analysis of digital waveform images by means of convolutional neural networks

AbstractAnalyzing seismic data to get information about earthquakes has always been a major task for seismologists and, more in general, for geophysicists. Recently, thanks to the technological development of observation systems, more and more data are available to perform such tasks. However, this data "grow up" makes "human possibility" of data processing more complex in terms of required efforts and time demanding. That is why new technological approaches such as artificial intelligence are becoming very popular and more and more exploited. In this paper, we explore the possibility of interpreting seismic waveform segments by means of pre-trained deep learning. More specifically, we apply convolutional networks to seismological waveforms recorded at local or regional distances without any pre-elaboration or filtering. We show that such an approach can be very successful in determining if an earthquake is "included" in the seismic wave image and in estimating the distance between the earthquake epicenter and the recording station

Large Earthquakes Recurrence Time in the Kefalonia Transform Fault Zone (KTFZ), Greece: Results from a physics-based simulator approach

Large earthquakes mean recurrence time (Tr) on specific fault segments is one of the primary input parameters for developing long-term Earthquake Rupture Forecast (ERF) models in a specific time span considering either a time-independent or an elastic rebound motivated renewal assumption. An attempt is made to define Tr on the major fault segments comprised in Kefalonia Transform Fault Zone (KTFZ), which is an active boundary demarcating from the west the area of central Ionian Islands, namely Lefkada and Kefalonia, and is associated with remarkably high seismic activity. Frequent large (Mw ≥ 6.0) earthquakes are reported to have caused severe damage during the last six centuries. Although the number of large earthquakes (including both historical and instrumental) is satisfactory enough for regional hazard studies, their number become very limited when they are subdivided into subsets assigned to specific fault segments. Physics-based earthquake simulators are approaches to overcome recurrence intervals shortage, due to their ability to generate long lasting earthquake catalogs. The application of a physics-based simulatorn the KTFZ, is attemped upon a detailed fault network model and implemented multiple times and with a wide range of input parameters, aiming at the definition of the most representative simulated catalog in respect to the observed regional seismicity. The most representative simulated catalog is finally used for investigating the recurrence behavior of large (Mw ≥ 6.0) earthquakes and assessing whether the renewal model performs better that the Poisson model, after considering both individual and multiple ruptured segments scenarios

Monitoring the vegetation stress coming from anthropogenic activities by modeling phenology using Sentinel-2 data

The study aimed at verifying the existence of stress induced on the functionality of natural ecosystems by particularly impacting anthropogenic activities. In detail, a methodology has been developed to evaluate any alterations in the phenology of plant species in areas surrounding sites defined by Italian legislation as “potentially polluted”. Specifically, the study areas located in Basilicata (southern Italy) were intended for municipal solid waste management activities and, at some stage of their management, Potential Toxic Elements (PTEs) concentrations were recorded above the thresholds permitted by the current legislation. The phenological trends of the vegetation were analyzed at gradually increasing distances from the centroid of the sites and then compared with points of the same type of vegetation, very distant from the sites, in areas that were not reasonably impacted by any contamination. The reconstruction of the phenological trends was carried out using Sentinel-2 images approximately on a monthly basis from which the Normalized Difference Vegetation Index (NDVI) was evaluated. Finally, the trends between areas adjacent the sites and unpolluted ones were statistically analyzed using dissimilarity indices which led to the conclusion of the non-existence of effects induced by PTEs on the functionality of the vegetation

Advancing the Frontiers of Earthquake Science

Statistical seismology has been emerging as a new discipline at the interface between earthquake physics, earthquake statistics, hazard assessment, and society. A workshop in Italy was sponsored by the Italian Istituto Nazionale di Geofisica e Vulcanologia (INGV), the Swiss Federal Institute of Technology Zurich (ETH), and the Japanese Institute of Statistical Mathematics (ISM), to discuss the state of the art and future directions. Conference participants discussed how to use available tools and techniques of statistical seismology to advance earthquake science. Building increasingly accurate timedependent earthquake forecast models at various spatial and temporal scales is widely recognized as an important challenge, and various such models were presented and discussed at the workshop. Exploiting time dependence for hazard assessment requires us to develop a detailed understanding of the behavior of regional fault systems and corresponding earthquake catalogs spanning decades. We can no longer analyze individual faults or earthquake sequences in isolation