Block Models of Lithosphere Dynamics and Seismicity

The necessity of catastrophe modeling is stipulated both by the essential increase of losses due to recent natural and anthropogenic hazards and by a lack of reliable real observation data. This paper focuses on risks of earthquakes. The region of Italy is considered as an example. A brief overview of different approaches in mathematical modeling of the lithosphere dynamics is presented. A model of the block structure dynamics and seismicity is described in detail and used for the analysis of the Vrancea (Romania) seismoactive region. The corresponding synthetic earthquake catalog is viewed as a basis for a possible generator of catastrophic events for estimating the seismic risks in the region

Lithosphere 2021 : Eleventh symposium on structure, composition and evolution of the lithosphere

Programme and extended abstract

NASA Geodynamics Program

Activities and achievements for the period of May 1983 to May 1984 for the NASA geodynamics program are summarized. Abstracts of papers presented at the Conference are inlcuded. Current publications associated with the NASA Geodynamics Program are listed

Coupled surface to deep Earth processes: Perspectives from TOPO-EUROPE with an emphasis on climate- and energy-related societal challenges

Understanding the interactions between surface and deep Earth processes is important for research in many diverse scientific areas including climate, environment, energy, georesources and biosphere. The TOPO-EUROPE initiative of the International Lithosphere Program serves as a pan-European platform for integrated surface and deep Earth sciences, synergizing observational studies of the Earth structure and fluxes on all spatial and temporal scales with modelling of Earth processes. This review provides a survey of scientific developments in our quantitative understanding of coupled surface-deep Earth processes achieved through TOPO-EUROPE. The most notable innovations include (1) a process-based understanding of the connection of upper mantle dynamics and absolute plate motion frames; (2) integrated models for sediment source-to-sink dynamics, demonstrating the importance of mass transfer from mountains to basins and from basin to basin; (3) demonstration of the key role of polyphase evolution of sedimentary basins, the impact of pre-rift and pre-orogenic structures, and the evolution of subsequent lithosphere and landscape dynamics; (4) improved conceptual understanding of the temporal evolution from back-arc extension to tectonic inversion and onset of subduction; (5) models to explain the integrated strength of Europe's lithosphere; (6) concepts governing the interplay between thermal upper mantle processes and stress-induced intraplate deformation; (7) constraints on the record of vertical motions from high-resolution data sets obtained from geo-thermochronology for Europe's topographic evolution; (8) recognition and quantifications of the forcing by erosional and/or glacial-interglacial surface mass transfer on the regional magmatism, with major implications for our understanding of the carbon cycle on geological timescales and the emerging field of biogeodynamics; and (9) the transfer of insights obtained on the coupling of deep Earth and surface processes to the domain of geothermal energy exploration. Concerning the future research agenda of TOPO-EUROPE, we also discuss the rich potential for further advances, multidisciplinary research and community building across many scientific frontiers, including research on the biosphere, climate and energy. These will focus on obtaining a better insight into the initiation and evolution of subduction systems, the role of mantle plumes in continental rifting and (super)continent break-up, and the deformation and tectonic reactivation of cratons; the interaction between geodynamic, surface and climate processes, such as interactions between glaciation, sea level change and deep Earth processes; the sensitivity, tipping points, and spatio-temporal evolution of the interactions between climate and tectonics as well as the role of rock melting and outgassing in affecting such interactions; the emerging field of biogeodynamics, that is the impact of coupled deep Earth – surface processes on the evolution of life on Earth; and tightening the connection between societal challenges regarding renewable georesources, climate change, natural geohazards, and novel process-understanding of the Earth system

Structure and tectonics of the crust and Moho discontinuity of the Gloria Fault and Terceira Rift (S. Miguel) along the Nubia-Eurasia plate boundary

The crustal structure of two ~150 km long segments across two main tectonic plate boundaries in the North Atlantic, the Gloria Fault and the Terceira Rift are presented. The Gloria Fault stands as a seismogenic fracture zone that generates high magnitude earthquakes, such as the M8.4 event in 1941. Vp and Vs waves were recorded during an active seismic refraction experiment using 18 Ocean Bottom Stations. The velocity model allows discrimination of five layers (L1 to L5), L1 for sediments, L2 for upper crust, L3 for lower crust, L4 for a layer of unknown origin and L5 for mantle. Poisson coefficient from Vp/Vs ratio allowed estimation of layers’ densities. We speculate on L4 origin and nature from velocities and densities. Two possible models, L4 corresponds to a mixture of gabbro and peridotite or to hydrated mantle (serpentinized mantle). The Terceira Rift seismic refraction line comprehends data from the S. Miguel Island. Velocities of S waves were not recorded. The model is based in Vp only. A five layer model is proposed, L1 for volcano-sedimentary layer, L2 for upper crust, L3 for lower crust and L5 for the mantle. L4 between L3 and L5 has a lensoid shape and its velocities suggest either a cumulate gabbro underplated layer or hydrated mantle. A south dipping extensional shear zone aligned with the Monaco Graben was identified from the brittle upper crust and across the lower crust, L4 and mantle. This shear zone coincides with a cluster of seismicity located to the south of S. Miguel Island. To the north of S. Miguel seismicity is barely inexistent and a 20 km long recent landslide with a toe thrust is clearly imaged, suggesting northward tilting of the island caused by the extensional shear zone, the south flank of the Terceira Rift.German Research Foundation, DFG, grant Hu698/19-

National Seismic System Science Plan

Recent developments in digital communication and seismometry are allowing seismologists to propose revolutionary new ways to reduce vulnerability from earthquakes, volcanoes, and tsunamis, and to better understand these phenomena as well as the basic structure and dynamics of the Earth. This document provides a brief description of some of the critical new problems that can be addressed using modem digital seismic networks. It also provides an overview of existing seismic networks and suggests ways to integrate these together into a National Seismic System. A National Seismic System will consist of a number of interconnected regional networks (such as southern California, central and northern California, northeastern United States, northwestern United States, and so on) that are jointly operated by Federal, State, and private seismological research institutions. Regional networks will provide vital information concerning the hazards of specific regions. Parts of these networks will be linked to provide uniform rapid response on a national level (the National Seismic Network). A National Seismic System promises to significantly reduce societal risk to earthquake losses and to open new areas of fundamental basic research. The following is a list of some of the uses of a National Seismic System