Search Results (6)

The accurate and timely estimation of earthquake magnitude is essential for effective tsunami early warning, particularly in seismically active regions such as Indonesia. Conventional seismic approaches are often hindered by magnitude saturation in significant events (Mw > 7.5), resulting in systematically underestimated magnitudes. To address this limitation, we develop a regional peak ground displacement (PGD) scaling law using high-rate GNSS (HR-GNSS) data from 21 moderate to large earthquakes in Indonesia. Based on 87 PGD observations, we construct a regression model that relates PGD, hypocentral distance, and moment magnitude (Mw). The PGD-derived magnitudes (MPGD) exhibit strong concordance with catalog moment magnitudes, achieving a mean absolute deviation (MAD) of 0.21 and surpassing the accuracy of previously published global models. Retrospective analyses reveal that MPGD estimates converge within 2–3 min for well-recorded events and remain robust, even for great and tsunamigenic earthquakes. These results underscore the potential of HR-GNSS data to complement conventional seismic networks, providing rapid and reliable magnitude estimates for operational tsunami early warning in Indonesia. Full article

The Global Historical Megatsunamis Catalog (GHMCat) is presented for the first time, including events with the largest waves recorded in historical times. An objective criterion is established to identify megatsunamis based on the maximum wave height (runup) of all recorded events. A threshold value of 35 m for maximum wave height is proposed based on the analysis of the statistical distribution of the maximum wave heights documented. The catalog was compiled through a systematic review and verification of tsunami events from the two existing Global Historical Tsunami Databases (GHTDs). A list of 40 megatsunamis from 1674 to the present is presented, including descriptions of their maximum wave heights, causes and sources according to the available and verified information, along with the main bibliographical references that support the data gathered in the catalog. The majority of megatsunamis have originated from large landslides, predominantly subaerial, with fewer caused by submarine landslides or associated with volcanic explosions. The geographical distribution of source locations shows that megatsunamis most frequently occur in bays and fjords in glaciated areas and in inland bodies of water, such as lakes and rivers. Notably, certain regions of Alaska and Norway experienced an unusual frequency of megatsunamis, particularly in the early 20th century. The information provided by the GHMCat allows for a comprehensive historical overview of megatsunamis, establishing relationships between their causes, wave heights, and geographic distribution over the past 350 years. This may contribute to advancing the study of the causes and origins of megatsunamis and aid in their prevention in high-risk regions. Full article

The 1755 Lisbon earthquake holds significant historical importance in Portuguese history. The subsequent tsunami resulted in extensive destruction and damage, affecting not only Lisbon but also other regions of Portugal, Spain, and North Africa. This significant and hazardous event led to an increase in awareness about earthquake and tsunami risks, not only within Portugal but throughout Europe. This heightened awareness facilitated advancements in scientific developments, including design codes, standards, and earthquake engineering. However, recent studies focusing on hazard assessment for Lisbon are limited. For this reason, this paper aims to present a comprehensive probabilistic seismic hazard analysis (PSHA) for the Lisbon metropolitan area. The first stage of PSHA involves defining applicable and active seismic source models (area and line sources) within the study area. Subsequently, historical and instrumental earthquake records are collected to build a homogenized earthquake catalog, utilizing both global and local earthquake databases. Following this, the completeness level of the earthquake catalog is tested. By incorporating suitable ground motion models to the region and local soil characteristics, seismic hazard maps for various return periods and hazard curves in terms of peak ground acceleration (PGA) are developed. The findings based on the area source model agree with existing literature, indicating PGA values ranging from 0.3 g to 0.9 g, 0.2 g to 0.7 g, 0.2 g to 0.5 g, and 0.1 g to 0.3 g for return periods of 2475, 975, 475, and 50 years, respectively. Full article

A new set of observations has been compiled for tsunamis occurring in Greece and in the surrounding areas from 1900 to 2023. A variety of information sources has been collected and examined, including scientific and press reports, books, eyewitness accounts, pictorial and video material, and tide-gauge records. New material was also collected during our field surveys in the islands of Cephalonia, Karpathos, and Kos. Our investigation included 26 distinct events and revealed several tsunamis. The majority of them have remained unknown so far in the tsunami community. Our compilation also included little-known events for which further documentation has been provided. Among others, of particular importance is the collection of new information about the well-known tsunami associated with the 9 February 1948 large earthquake in Karpathos Island as well as the unknown so far series of local but powerful tsunamis generated during the seismic crisis of very strong earthquakes that destroyed the Ionian islands during August 1953. The new observational material collected is significant for the enrichment of existing tsunami catalogs with positive implications for better understanding the tsunami generation mechanisms and the assessment of tsunami hazards and risks. Full article

Due to their geographical condition and worldwide environmental protection policies, the Galapagos Islands must opt for implementing clean energy infrastructure considering natural hazard effects that can directly affect the resilience of community residents. Santa Cruz Island is part of this archipelago, with rich biodiversity in flora and unique fauna. This study proposes identifying earthquake and tsunami risk assessment components on the island, such as the infrastructure vulnerability of Puerto Ayora, the central city of Santa Cruz Island. The FEMA P-154 and FEMA P-646 methodologies are used to classify buildings for technically installing microgrids based on photovoltaic generation systems. For this purpose, maps and data from state entities are used in combination with catalogs from development and land use planning, Software for Geoprocesses and virtual tours, and cadastral information provided by the Decentralized Autonomous Government (GAD) of Santa Cruz to develop techniques that offer a risk index to identify buildings that could sustain seismic and tsunamic loads. The study exposes alarming results that would prevent the installation of photovoltaic generation systems on the buildings’ roofs. Consequently, a more detailed field study is recommended to contrast the reported analysis to implement mitigation strategies accordingly. Finally, geoprocesseced maps are presented, in addition to general installing recommendations for the photovoltaic system’s infrastructure. Full article

Although tsunamis in the Black Sea are rare and less destructive, recently, their study has been the subject of interest due to the increasing concentration of population and infrastructure in low-lying coastal areas. This study aims to elucidate the spatial–temporal characteristics of earthquakes in the Black Sea region (27° E–42° E and 40° N–47° N) over a century to clarify the seismicity pattern further to be used for probabilistic seismic and tsunami hazard analysis. Significant volumes of seismic data from international and national databases were analyzed, and the results obtained from previous research were supplemented and expanded. Earthquakes over the period 1905–2022 from eight up-to-date seismic catalogs were used to compile a unified catalog after conversion to the moment magnitude scale Mw. The best-fit linear relationship between several magnitude scales and Mw was determined using the general orthogonal regression (GOR) and the least squares method (LSM). After the declustering procedure, the compiled catalog consists of 18,528 unique events. To assess the catalog data quality, the magnitude of completeness Mc was estimated for the entire catalog (1905–2022) and the so-called instrumental catalog (1977–2022). In addition, the spatial distribution of the completeness magnitude Mc and the recurrence b-plot slope in the Gutenberg–Richter distribution law were assessed using the goodness-of-fit and maximum likelihood methods from the instrumental catalog data. Finally, the most significant earthquakes within the Black Sea boundaries were estimated with their parameters and focal mechanisms. A possibility of the realization of strong quakes in the near future with tsunamigenic potential in the Black Sea region was concluded. Full article