Long-Term Seismic Activity and Present Microseismicity on Active Faults in Southwest Japan

1985 ◽  
pp. 253-284
Author(s):  
Tameshige Tsukuda
Keyword(s):  
Seismic Activity ◽  
Active Faults ◽  
Southwest Japan

scholarly journals Active Fault Systems in the Inner Northwest Apennines, Italy: A Reappraisal One Century after the 1920 Mw ~6.5 Fivizzano Earthquake

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 139
Author(s):  
Giancarlo Molli ◽  
Isabelle Manighetti ◽  
Rick Bennett ◽  
Jacques Malavieille ◽  
Enrico Serpelloni ◽  
...  
Keyword(s):  
Large Scale ◽  
Active Fault ◽  
Active Faults ◽  
Dense Network ◽  
Earthquake Fault ◽  
Slip Rates ◽  
Fault Systems ◽  
Seismological Data ◽  
Seismogenic Faults

Based on the review of the available stratigraphic, tectonic, morphological, geodetic, and seismological data, along with new structural observations, we present a reappraisal of the potential seismogenic faults and fault systems in the inner northwest Apennines, Italy, which was the site, one century ago, of the devastating Mw ~6.5, 1920 Fivizzano earthquake. Our updated fault catalog provides the fault locations, as well as the description of their architecture, large-scale segmentation, cumulative displacements, evidence for recent to present activity, and long-term slip rates. Our work documents that a dense network of active faults, and thus potential earthquake fault sources, exists in the region. We discuss the seismogenic potential of these faults, and propose a general tectonic scenario that might account for their development.

scholarly journals Impact of earthquake-triggered landslides on catchment sediment yield

2015 ◽  
Vol 367 ◽  
pp. 291-296
Author(s):  
M. Vanmaercke ◽  
F. Obreja ◽  
J. Poesen
Keyword(s):  
Sediment Yield ◽  
Seismic Activity ◽  
Fold Increase ◽  
Sediment Concentration ◽  
Spatial And Temporal Variation ◽  
Strongly Correlated ◽  
Before And After ◽  
Sediment Export

Abstract. This study explores the role of seismic activity in explaining spatial and temporal variation in sediment export from the Siret basin in Romania. Based on long-term (>30 years) sediment export measurements for 38 subcatchments, we found that spatial variation in sediment yield (SY) is strongly correlated to the degree of seismic activity and catchment lithology. Combined, these factors explain 80% of the variation in SY. To investigate the role of earthquake-triggered landslides in explaining these correlations, we studied the temporal variability in sediment concentrations before and after the 7.4 Mw earthquake of 1977 for ten subcatchments. Despite the fact that this earthquake triggered many landslides, only one subcatchment showed a clear (3-fold) increase in sediment concentration per unit discharge after the earthquake. This shows that, although prolonged seismic activity strongly controls average SY, individual earthquakes do not necessarily affect sediment export at short timescales.

scholarly journals Monitoring long-term changes of glacial seismic activity with continuous seismological observations: a case study from Spitsbergen

2016 ◽  
Author(s):  
W. Gajek ◽  
J. Trojanowski ◽  
M. Malinowski
Keyword(s):  
Seismic Activity ◽  
Seismic Station ◽  
Flow Analysis ◽  
Seismic Signal ◽  
Signal Frequency ◽  
Steady Increase ◽  
Fuzzy Logic Algorithm ◽  
Temperature And Precipitation ◽  
Seismological Data

Abstract. Changes in the global temperature balance have proved to have a major impact on the cryosphere and therefore retreating glaciers are the symbol of the warming climate. Long-term measurements of geophysical parameters provide the insight into the dynamics of those processes over many years. Here we explore the possibility of using data recorded by permanent seismological stations to monitor glacial seismic activity. Our study focuses on year-to-year changes in seismicity of the Hansbreen glacier (southern Spitsbergen). We have processed 7-year-long continuous seismological data recorded by a broadband station located in the fjord of Hornsund, obtaining seismicity distribution between 2008 and 2014. To distinguish between glacier- and non-glacier-origin events with the data from only one seismic station in the area, we developed a new fuzzy logic algorithm based on the seismic signal frequency and the energy flow analysis. Our research has revealed that the number of detected glacier-origin events over the last two years has doubled. We also observed that the annual events distribution correlates well with the temperature and precipitation data. In order to further support our observations, we have analysed 5-year-long seismological data recorded by a broadband station located in Ny-Ålesund (western Spitsbergen). Distribution of glacier-origin tremors detected in the vicinity of the Kronebreen glacier shows a steady increase from year to year, however not as significant as for the Hornsund dataset.

scholarly journals Tectonic stress regime in the 2003–2004 and 2012–2015 earthquake swarms in the Ubaye Valley, French Alps

2018 ◽  
Vol 175 (6) ◽  
pp. 1997-2008 ◽  
Author(s):  
Lucia Fojtíková ◽  
Václav Vavryčuk
Keyword(s):  
Seismic Activity ◽  
Joint Inversion ◽  
Earthquake Swarm ◽  
Active Faults ◽  
Tectonic Stress ◽  
Geological Mapping ◽  
Earthquake Swarms ◽  
Stress Regime ◽  
French Alps ◽  
Principal Axes

Abstract We study two earthquake swarms that occurred in the Ubaye Valley, French Alps within the past decade: the 2003–2004 earthquake swarm with the strongest shock of magnitude ML = 2.7, and the 2012–2015 earthquake swarm with the strongest shock of magnitude ML = 4.8. The 2003–2004 seismic activity clustered along a 9-km-long rupture zone at depth between 3 and 8 km. The 2012–2015 activity occurred a few kilometres to the northwest from the previous one. We applied the iterative joint inversion for stress and fault orientations developed by Vavryčuk (2014) to focal mechanisms of 74 events of the 2003–2004 swarm and of 13 strongest events of the 2012–2015 swarm. The retrieved stress regime is consistent for both seismic activities. The σ 3 principal axis is nearly horizontal with azimuth of ~ 103°. The σ 1 and σ 2 principal axes are inclined and their stress magnitudes are similar. The active faults are optimally oriented for shear faulting with respect to tectonic stress and differ from major fault systems known from geological mapping in the region. The estimated low value of friction coefficient at the faults 0.2–0.3 supports an idea of seismic activity triggered or strongly affected by presence of fluids.

Seismic velocity precursors to the 2016 Mw 6.5 Norcia (Italy) earthquake

Geology ◽  
2020 ◽  
Vol 48 (9) ◽  
pp. 924-928 ◽  
Author(s):  
C. Chiarabba ◽  
P. De Gori ◽  
M. Segou ◽  
M. Cattaneo
Keyword(s):  
Seismic Velocity ◽  
Time Windows ◽  
Central Italy ◽  
Active Faults ◽  
Central Italy Earthquake ◽  
Preparatory Phase ◽  
Triggering Mechanisms ◽  
Failure Conditions ◽  
Deformation Patterns

Abstract Earthquakes occur as the result of long-term strain accumulation on active faults and complex transient triggering mechanisms. Although laboratory experiments show accelerating deformation patterns before failure conditions are met, imaging similar preparatory phases in nature remains difficult because it requires dense monitoring in advance. The 2016 Amatrice-Visso-Norcia (central Italy) earthquake cascade, captured by an unprecedented seismic network, provided a unique testing ground to image the preparatory phase of a large event. The crustal volume of the Norcia incipient fault was densely illuminated by seismic rays from more than 13,000 earthquakes that occurred within the 3 mo before the main shock nucleation. We performed seismic tomography in distinct time windows that revealed the precursory changes of elastic wave speed, signaling (1) the final locked state of the fault, and (2) the rapid fault-stiffness alterations near the hypocenter just a few weeks before the event. The results are the first instance where short-lived, hard-to-catch crustal properties shed light on evolving earthquake cascades.

Current R & D Activities in the Study on Geosphere Stability

2010 ◽  
Author(s):  
Takahiro Hanamuro ◽  
Ken-Ichi Yasue ◽  
Yoko Saito-Kokubu ◽  
Koichi Asamori ◽  
Tsuneari Ishimaru ◽  
...  
Keyword(s):  
Prediction Model ◽  
Hot Spring ◽  
Active Faults ◽  
Hydrogen Gas ◽  
Helium Isotope ◽  
Sea Level Changes ◽  
Detection Techniques ◽  
Geothermal Activity ◽  
The Future

The Japanese islands are located in a tectonically active zone. The scientific base is required for assessing the geosphere stability for long-term isolation of radioactive waste in Japan. JAEA is promoting the establishment of investigation method for geotectonic events affecting geosphere stability and prediction model for the future changes of geological environments, that is necessary for site selection and safety assessment of the HLW geological disposal. For seismicity and faulting, detection techniques for active faults without topographic surface expression, such as using helium isotope ratios in hot spring gases or detection of hydrogen gas, and studies on the assessment of fault evolution have been developed. For volcanism and geothermal activity, heat sources for anomalous geothermal activity in non-volcanic regions are considered. Detection techniques for high-temperature fluids and magma deep underground, using geophysical and geochemical approaches, were constructed. For uplift, denudation and climatic/sea-level changes, a methodology to predict the future topographic change was developed. Also, for dating techniques as an essential part to proceed on these studies, C-14 and Be-10 dating using AMS and (U-Th)/He dating using QMS and ICP-MS have been developed. We are planning the establishment of assessment methods for geosphere stability including assessment of the activity of faults encountered in underground excavations, development of long-term prediction model of volcanism and hydrothermal activities, and hydrogeological analyses considering topographic change.

Correlation between the Fluctuations in Worldwide Seismicity and in Atmospheric Carbon Pollution

Sci ◽  
2018 ◽  
Vol 1 (1) ◽  
pp. 2
Author(s):  
Alberto Carpinteri ◽  
Gianni Niccolini
Keyword(s):  
Growth Rate ◽  
Time Series ◽  
Seismic Activity ◽  
Active Faults ◽  
Earth’S Crust ◽  
Atmospheric Co2 ◽  
Geochemical Evolution ◽  
Geochemical Data ◽  
Anthropogenic Emissions ◽  
Earth's Crust

The crucial stages in the geochemical evolution of the Earth’s crust, ocean, and atmosphere could be explained by the assumed low-energy nuclear reactions (LENR) that are triggered by seismic activity. LENR result in the fission of medium-weight elements accompanied by neutron emissions, involving Fe and Ni as starting elements, and C, N, O as resultants. Geochemical data and experimental evidences support the LENR hypothesis. The time series analysis highlighted significant correlation between the atmospheric CO2 growth rate and the global seismic-moment release rate, whereas the trending behavior was in response to the anthropogenic emissions. The fluctuations in the atmospheric CO2 growth rate time series were inexplicable in terms of anthropogenic emissions, but could be explained by the cycles of worldwide seismicity, which massively trigger LENR in the Earth’s crust. In this framework, LENR from active faults must be considered as a relevant cause of carbon formation and degassing of freshly-formed CO2 during seismic activity.

scholarly journals Integrating faults and past earthquakes into a probabilistic seismic hazard model for peninsular Italy

2017 ◽  
Vol 17 (11) ◽  
pp. 2017-2039 ◽  
Author(s):  
Alessandro Valentini ◽  
Francesco Visini ◽  
Bruno Pace
Keyword(s):  
Seismic Hazard ◽  
Seismic Activity ◽  
Grid Point ◽  
Active Faults ◽  
Gaussian Model ◽  
Probabilistic Seismic Hazard ◽  
Maximum Magnitude ◽  
Slip Rates ◽  
Earthquake Sources ◽  
The Impact

Abstract. Italy is one of the most seismically active countries in Europe. Moderate to strong earthquakes, with magnitudes of up to ∼ 7, have been historically recorded for many active faults. Currently, probabilistic seismic hazard assessments in Italy are mainly based on area source models, in which seismicity is modelled using a number of seismotectonic zones and the occurrence of earthquakes is assumed uniform. However, in the past decade, efforts have increasingly been directed towards using fault sources in seismic hazard models to obtain more detailed and potentially more realistic patterns of ground motion. In our model, we used two categories of earthquake sources. The first involves active faults, and using geological slip rates to quantify the seismic activity rate. We produced an inventory of all fault sources with details of their geometric, kinematic, and energetic properties. The associated parameters were used to compute the total seismic moment rate of each fault. We evaluated the magnitude–frequency distribution (MFD) of each fault source using two models: a characteristic Gaussian model centred at the maximum magnitude and a truncated Gutenberg–Richter model. The second earthquake source category involves grid-point seismicity, with a fixed-radius smoothed approach and a historical catalogue were used to evaluate seismic activity. Under the assumption that deformation is concentrated along faults, we combined the MFD derived from the geometry and slip rates of active faults with the MFD from the spatially smoothed earthquake sources and assumed that the smoothed seismic activity in the vicinity of an active fault gradually decreases by a fault-size-driven factor. Additionally, we computed horizontal peak ground acceleration (PGA) maps for return periods of 475 and 2475 years. Although the ranges and gross spatial distributions of the expected accelerations obtained here are comparable to those obtained through methods involving seismic catalogues and classical zonation models, the spatial pattern of the hazard maps obtained with our model is far more detailed. Our model is characterized by areas that are more hazardous and that correspond to mapped active faults, while previous models yield expected accelerations that are almost uniformly distributed across large regions. In addition, we conducted sensitivity tests to determine the impact on the hazard results of the earthquake rates derived from two MFD models for faults and to determine the relative contributions of faults versus distributed seismic activity. We believe that our model represents advancements in terms of the input data (quantity and quality) and methodology used in the field of fault-based regional seismic hazard modelling in Italy.

scholarly journals Correlation between the Fluctuations in Worldwide Seismicity and Atmospheric Carbon Pollution

Sci ◽  
2019 ◽  
Vol 1 (1) ◽  
pp. 2 ◽  
Author(s):  
Alberto Carpinteri ◽  
Gianni Niccolini
Keyword(s):  
Seismic Activity ◽  
Nuclear Reactions ◽  
Active Faults ◽  
Earth’S Crust ◽  
Atmospheric Co2 ◽  
Geochemical Evolution ◽  
Geochemical Data ◽  
Common Cycles ◽  
Earth's Crust ◽  
Seismic Moment Release

The crucial stages in the geochemical evolution of the Earth’s crust, ocean, and atmosphere could be explained by the assumed low-energy nuclear reactions (LENR) that are triggered by seismic activity. LENR result in the fission of medium-weight elements accompanied by neutron emissions, involving Fe and Ni as starting elements, and C, N, O as resultants. Geochemical data and experimental evidences support the LENR hypothesis. A spectral analysis of the period 1955-2013 shows common cycles between interannual changes in atmospheric CO2 growth rate and global seismic-moment release, whereas the trending behavior of the atmospheric CO2 was in response to the anthropogenic emissions. Assuming a correlation between such seismic and atmospheric fluctuations, the latter could be explained by cycles of worldwide seismicity, which would trigger massively LENR in the Earth’s Crust. In this framework, LENR from active faults could be considered as a relevant cause of carbon formation and degassing of freshly-formed CO2 during seismic activity. However, further studies are necessary to validate the present hypothesis which, at the present time, mainly aims to stimulate debate on the models which regulates atmospheric CO2.

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