0 INTRODUCTION Pore-pressure change,which reduces effective normal stress,is a key aftershock trigger,particularly in extensional settings(Miller etal.,2004).Other proposed mechanisms include coseismic stress perturba...0 INTRODUCTION Pore-pressure change,which reduces effective normal stress,is a key aftershock trigger,particularly in extensional settings(Miller etal.,2004).Other proposed mechanisms include coseismic stress perturbations,aseismic slip,and viscoelastic relaxation(Bai et al.,2025;Hu et al.,2025;Perfettini and Avouac,2004;Stein,1999).Determining the dominant mechanism for any event is a critical challenge for understanding regional seismotectonics and assessing evolving hazards.展开更多
In this paper, we calculated Bouguer gravity anomalies and Airy-Heiskanen isostatic anomalies in the New Britain Trench and surrounding areas of Papua New Guinea. The calculations are based on a topographic model and ...In this paper, we calculated Bouguer gravity anomalies and Airy-Heiskanen isostatic anomalies in the New Britain Trench and surrounding areas of Papua New Guinea. The calculations are based on a topographic model and a gravity anomaly model from the Scripps Institute of Oceanography. Characteristics of the isostatic anomaly and the earthquake dynamic environment of this region are analyzed,and the results show that there are obvious differences in the isostatic state between each block in the region. Tectonic movements are very intense in regions with high positive or negative isostatic gravity anomalies, and a number of sub-plates in this area are driven by external tectonic action, such as plate subduction and thrusting, of the Pacific, Indo-Australian and Eurasian plates. From the distribution of the isostatic gravity anomaly, the tectonic action of anti-isostatic movement obviously is the main source of power. Based on isostatic gravity and spatial distribution of earthquakes in the region, it is obvious that further contraction of the Indo-Australian Plate will result in the southwestern part of the Solomon Plate becoming part of the Owen Stanley thrust belt, and the northern part will enter the lower part of the Bismarck Plate. The eastern part of the Solomon Plate will enter the front of the Pacific Plate, resulting in northward and eastward migration of significant earthquakes along the Solomon Plate.展开更多
The Northe South Seismic Belt(NSSB) is a Chinese tectonic boundary with a very complex structure, showing a sharp change in several geophysical field characteristics. To study these characteristics and their relations...The Northe South Seismic Belt(NSSB) is a Chinese tectonic boundary with a very complex structure, showing a sharp change in several geophysical field characteristics. To study these characteristics and their relationship with the distribution of earthquakes and faults in the study area, we first analyze the spatial gravity anomaly to achieve the Bouguer gravity anomaly(EGM2008 BGA) and the regional gravity survey Bouguer gravity anomaly.Next, we ascertain the Moho depth and crustal thickness of the study area using interface inversion with the control points derived from the seismic and magnetotelluric sounding profiles achieved in recent years. In this paper, we summarize the relief, trend, Moho gradient, and crustal nature, in addition to their relationship with the distribution of earthquakes and faults in the study area. The findings show that earthquakes with magnitudes greater than Ms7.0 are mainly distributed in the Moho Bouguer anomaly variation belt and faults. The results of the study are important for future research on tectonic characteristics, geological and geophysical surveys, and seismicity patterns.展开更多
MASSIVE （mapping seismic vulnerability and risk of cities） is a GIS-based earthquake preparedness system that was developed under the European Union Civil Protection Mechanism project （GA No. 070401/2009/540429/SUB...MASSIVE （mapping seismic vulnerability and risk of cities） is a GIS-based earthquake preparedness system that was developed under the European Union Civil Protection Mechanism project （GA No. 070401/2009/540429/SUB/A4）, in order to provide civil protection authorities with accurate, and easily transferable tools for generating up-to-date maps of seismic hazard, seismic vulnerability and seismic risk of buildings, at the scale of the single building block. In addition, MASSIVE developed and ran state-of-the-art models to assess the risk for population evacuation in dense urban agglomerations given an earthquake event. The MASSIVE methodology was designed, implemented and validated considering two European pilot sites, heavily struck by recent earthquakes, which are the western part of the Larger Metropolitan Area of Athens （GR）, and the city of L＇ Aquila in the Abruzzo Region （IT）. The validation of the results using past earthquake records shows that the performance of MASSIVE is prosperous, achieving a correlation between the modeled and the on-site measured PGAs （peak ground accelerations） higher than 0.75, while the correlation between the on-site reported building damages and the ones predicted by the MASSIVE system has been of the order of 0.80.展开更多
Sichuan-Yunnan region in China, a tectonic transition belt where earthquakes occurred frequently and intensely, has a distinct variation characteristic of gradient zone of Bouguer gravity anomaly （BGA）. Many deep fa...Sichuan-Yunnan region in China, a tectonic transition belt where earthquakes occurred frequently and intensely, has a distinct variation characteristic of gradient zone of Bouguer gravity anomaly （BGA）. Many deep faults and epicenters of severe earthquake scatter along the BGA gradient zones. Here we apply two forward models （Airy model and Vening Meinesz model） of isostatic gravity mechanisms （local versus regional） in this region to calculated the isostatic gravity anomaly （IGA）. Afterwards, the relationship between IGA and distribution of faults as well as seismicity is also illustrated. The IGA results show that the two models are similar and most parts of the study area are in an isostatic state. Most featured faults are distributed along the steep anomaly gradient zones; earthquakes tend to occur in the non-isostatic area and steep gradient belt of IGA. The distribution of root thickness based on regional mechanism can be associated with the main trend of BGA variation. The regional mechanism is more plausible and closer to the reality because of its relatively further consideration of the horizontal forces derived from adjacent particles in the crust. Then we analyze the effect of isostasy on the tectonic movements and find that the isostatic adjustment is not the main cause of the continuous uplift process of Longmenshan Mountain fault zone. which is due to the Indian-Eurasian continental collision.展开更多
We examined the whole strong earthquake recurrence behaviors of two fault zones along the Kefallinia Transform, Ionian Sea, Greece, using seismological data and statistical methods. Our data include 29 events with M ...We examined the whole strong earthquake recurrence behaviors of two fault zones along the Kefallinia Transform, Ionian Sea, Greece, using seismological data and statistical methods. Our data include 29 events with M 〉 5.5 for the period 1636 - 2003. We found different recurrence behaviors for the Kefallinia Fault Zone （clustering and time-predictable recurrence behaviors） and the Letkada Fault Zone （near random and non-slip-predictable or non-time-predictable recurrence nature）. The different modes may be attributed to： （a） segment interaction along-strike （Kefallinia） by static triggering and （b） the influence of fault systems to the north and east on the recurrence on Lefkada. Within the active periods, earthquake recurrence intervals are distributed in a more dispersed fashion, and can be fitted well by a Weibull distribution. In contrast, the distribution of the quiet periods is relatively less dispersed and difficult to describe by suitable probability functions.展开更多
In this paper, the admittance function between seafloor undulations and vertical gravity gradient anomalies was derived. Based on this admittance function, the bathymetry model of 1 minute resolution was predicted fro...In this paper, the admittance function between seafloor undulations and vertical gravity gradient anomalies was derived. Based on this admittance function, the bathymetry model of 1 minute resolution was predicted from vertical gravity gradient anomalies and ship soundings in the experimental area from the northwest Pacific. The accuracy of the model is evaluated using ship soundings and existing models, including ETOPO1, GEBCO, DTU10 and V15.1 from SIO. The model＇s STD is 69. 481m, comparable with V15.1 which is generally believed to have the highest accuracy.展开更多
As is well known, Greece has a significant number of earthquakes each year. Ιn recent years, several earthquakes have occurred in Greece. For this scope, a methodology was used to determine the source parameters. Thi...As is well known, Greece has a significant number of earthquakes each year. Ιn recent years, several earthquakes have occurred in Greece. For this scope, a methodology was used to determine the source parameters. This methodology is based on minimizing the difference between the observed and the synthetic waveforms, using the method Source Parameters Calculation—SPCa <a href="#ref1" target="_blank">[1]</a>. The source parameters, using the proposed methodology, are calculated by comparing observed seismograms and synthetic by inverting data. The synthetics are calculated using the reflectivity method (Kennett, 1983) as implemented by Randall et al. (1994) for a given earth structure. This study includes inversion results for the strongest events that occurred in Greece from 2008 to 2014. For the same events calculated the main fault plane, using the method of Hypocenter Centroid-plot (HC-plot) <a href="#ref2" target="_blank">[2]</a> <a href="#ref3" target="_blank">[3]</a>. This methodology is a simple geometrical method based on the combination between the hypocentral position and the two possible fault planes.展开更多
The crustal structures of P velocity and density on the deep seismic sounding profile across the Dabieshan erogenic belt are presented. There is a 5-km-thick crustal "root" between the Yuexi and Xiaotian whe...The crustal structures of P velocity and density on the deep seismic sounding profile across the Dabieshan erogenic belt are presented. There is a 5-km-thick crustal "root" between the Yuexi and Xiaotian where the elevation is highest on the profile. An apparent Moho offset of 4.5 km beneath the Xiaotian-Mozitan fault marks the paleo-suture of the Triassic collision. A high-velocity anomaly zone at the depth below 3 km beneath the ultra-high pressure (UHP) zone may be correlated to the higher content of UHP metamorphic rocks.展开更多
This study focuses on defining rates of fluvial incision for the last 580±5 kyr along valley systems of eight streams that drain the eastern part of the northern Peloponnese. The streams are developed on the upli...This study focuses on defining rates of fluvial incision for the last 580±5 kyr along valley systems of eight streams that drain the eastern part of the northern Peloponnese. The streams are developed on the uplifted block of the offshore-running Xylokastro normal fault, one of the main faults bounding the southern edge of the Gulf of Corinth half-graben, and have incised a set of ten uplifted marine terraces having an amphitheatric shape. These terraces range in age from 60±5 kyr to 580±5 kyr and have been mapped in detail and correlated with late Pleistocene oxygen-isotope stages of high sea-level stands by previous studies. The terraces were used in this paper as reference surfaces in order to define fluvial incision rates at the lower reaches of the studied streams. To evaluate incision rates, thirty-three topographic valley cross-sec- tions were drawn using fieldwork measurements as well as using a highly accurate （2×2 cell size） Digital Elevation Model （DEM） at specific locations where streams cut down the inner edges of the marine terraces. For each cross-section the ratio of valley floor width to valley height （Vf） and long-term mean stream incision rates were estimated for the last 580±5 kyr, while rock uplift rates were estimated for the last 330±5 kyr. The geomorphic evolution of the valleys on the uplifted block of the Xylokastro fault has been mainly driven by the lithology of the bedrock, sea level fluctuations during the late Quaternary, and incision of the channels due to the tectonic uplift. Stream incision rates range from 0.10±0.1 mm/yr for the last 123±7 kyr to 1.14±0.1 mm/yr for the last 310±5 kyr and are gradually greater from east to west depending on the distance from the trace of the fault.Downcutting rates are comparable with the rock uplift rates, which range from 0.4±0.02 mm/yr to 1.49±0.12 mm/yr, over the last 330±5 kyr.展开更多
During August 1953 three strong earthquakes of magnitude ranging from 6.3 to 7.2 shook the Ionian Island of Cephalonia （Kefalonia）, Greece, and destroyed almost the entire building stock of the Island which consiste...During August 1953 three strong earthquakes of magnitude ranging from 6.3 to 7.2 shook the Ionian Island of Cephalonia （Kefalonia）, Greece, and destroyed almost the entire building stock of the Island which consisted primarily of traditional unreinforced masonry （URM） houses. The authorities went on to restructuring of the building stock, using a structural system that is most like what is known today as confined masonry. They designed about 14 types of one- to two-storey buildings providing the engineers with detailed construction plans. These buildings are known as ＂Arogi＂ buildings （Arogi in Greek meaning Aid）. On the 24th of January and 3rd of February 2014, two earthquakes of magnitude 6.1 and 6.0 struck the island, causing significant soil damages, developing excessively high ground accelerations. Surprisingly, no damage was reported in the ＂Arogi＂ buildings. The seismic behavior of the buildings is examined by FEM linear analysis and it is compared to that of URM structures. Computed results illustrate that the displacements of identical URM buildings would be about twice the magnitudes observed in the corresponding ＂Arogi＂ ones, with the implication that the earthquake sequence of 2014 would have caused critical damage should the type of structure be of the URM type. Furthermore, it is illustrated that this low cost alternative method of construction is a very effective means of producing earthquake resilient structures, whereas further reduction of seismic displacement may be achieved in the order of 50% with commensurate effects on damage potential, when reinforced slabs are used to replace the timber roofs.展开更多
基金supported by the National Natural Science Foundation of China(Nos.42174023,42030108)the State Key Laboratory of Geohazard Prevention and Geoenvironment Protection Independent Research Project(No.SKLGP2024Z016)Sichuan Province Science Fund(No.2024NSFSC0802).
文摘0 INTRODUCTION Pore-pressure change,which reduces effective normal stress,is a key aftershock trigger,particularly in extensional settings(Miller etal.,2004).Other proposed mechanisms include coseismic stress perturbations,aseismic slip,and viscoelastic relaxation(Bai et al.,2025;Hu et al.,2025;Perfettini and Avouac,2004;Stein,1999).Determining the dominant mechanism for any event is a critical challenge for understanding regional seismotectonics and assessing evolving hazards.
基金supported by the Science for Earthquake Resilience(XH17022)
文摘In this paper, we calculated Bouguer gravity anomalies and Airy-Heiskanen isostatic anomalies in the New Britain Trench and surrounding areas of Papua New Guinea. The calculations are based on a topographic model and a gravity anomaly model from the Scripps Institute of Oceanography. Characteristics of the isostatic anomaly and the earthquake dynamic environment of this region are analyzed,and the results show that there are obvious differences in the isostatic state between each block in the region. Tectonic movements are very intense in regions with high positive or negative isostatic gravity anomalies, and a number of sub-plates in this area are driven by external tectonic action, such as plate subduction and thrusting, of the Pacific, Indo-Australian and Eurasian plates. From the distribution of the isostatic gravity anomaly, the tectonic action of anti-isostatic movement obviously is the main source of power. Based on isostatic gravity and spatial distribution of earthquakes in the region, it is obvious that further contraction of the Indo-Australian Plate will result in the southwestern part of the Solomon Plate becoming part of the Owen Stanley thrust belt, and the northern part will enter the lower part of the Bismarck Plate. The eastern part of the Solomon Plate will enter the front of the Pacific Plate, resulting in northward and eastward migration of significant earthquakes along the Solomon Plate.
基金supported by the China Earthquake Administration, Institute of Seismology Foundation (201326126)Institute of Seismology Foundation (201326128)Chinese earthquake scientific array exploration e northern section of North South seismic belt gravity profile Foundation (201308011)
文摘The Northe South Seismic Belt(NSSB) is a Chinese tectonic boundary with a very complex structure, showing a sharp change in several geophysical field characteristics. To study these characteristics and their relationship with the distribution of earthquakes and faults in the study area, we first analyze the spatial gravity anomaly to achieve the Bouguer gravity anomaly(EGM2008 BGA) and the regional gravity survey Bouguer gravity anomaly.Next, we ascertain the Moho depth and crustal thickness of the study area using interface inversion with the control points derived from the seismic and magnetotelluric sounding profiles achieved in recent years. In this paper, we summarize the relief, trend, Moho gradient, and crustal nature, in addition to their relationship with the distribution of earthquakes and faults in the study area. The findings show that earthquakes with magnitudes greater than Ms7.0 are mainly distributed in the Moho Bouguer anomaly variation belt and faults. The results of the study are important for future research on tectonic characteristics, geological and geophysical surveys, and seismicity patterns.
文摘MASSIVE （mapping seismic vulnerability and risk of cities） is a GIS-based earthquake preparedness system that was developed under the European Union Civil Protection Mechanism project （GA No. 070401/2009/540429/SUB/A4）, in order to provide civil protection authorities with accurate, and easily transferable tools for generating up-to-date maps of seismic hazard, seismic vulnerability and seismic risk of buildings, at the scale of the single building block. In addition, MASSIVE developed and ran state-of-the-art models to assess the risk for population evacuation in dense urban agglomerations given an earthquake event. The MASSIVE methodology was designed, implemented and validated considering two European pilot sites, heavily struck by recent earthquakes, which are the western part of the Larger Metropolitan Area of Athens （GR）, and the city of L＇ Aquila in the Abruzzo Region （IT）. The validation of the results using past earthquake records shows that the performance of MASSIVE is prosperous, achieving a correlation between the modeled and the on-site measured PGAs （peak ground accelerations） higher than 0.75, while the correlation between the on-site reported building damages and the ones predicted by the MASSIVE system has been of the order of 0.80.
基金supported by the China Earthquake Administration,Institute of Seismology Foundation(IS201416141)Spark Plan(XH17022)
文摘Sichuan-Yunnan region in China, a tectonic transition belt where earthquakes occurred frequently and intensely, has a distinct variation characteristic of gradient zone of Bouguer gravity anomaly （BGA）. Many deep faults and epicenters of severe earthquake scatter along the BGA gradient zones. Here we apply two forward models （Airy model and Vening Meinesz model） of isostatic gravity mechanisms （local versus regional） in this region to calculated the isostatic gravity anomaly （IGA）. Afterwards, the relationship between IGA and distribution of faults as well as seismicity is also illustrated. The IGA results show that the two models are similar and most parts of the study area are in an isostatic state. Most featured faults are distributed along the steep anomaly gradient zones; earthquakes tend to occur in the non-isostatic area and steep gradient belt of IGA. The distribution of root thickness based on regional mechanism can be associated with the main trend of BGA variation. The regional mechanism is more plausible and closer to the reality because of its relatively further consideration of the horizontal forces derived from adjacent particles in the crust. Then we analyze the effect of isostasy on the tectonic movements and find that the isostatic adjustment is not the main cause of the continuous uplift process of Longmenshan Mountain fault zone. which is due to the Indian-Eurasian continental collision.
基金This paper is part result of the program"Investigation of recurrence modes of large earthquakes alongthe main seismogenic faults in Greece andin China"(20051696) in the frame of bilateral cooperation between China and Greece inthefield of seismology and geophysics sponsored bythe Ministry of Science and Technologyof China This programis mainlyfunded bythe NSF40674024 and the NSF40374019
文摘We examined the whole strong earthquake recurrence behaviors of two fault zones along the Kefallinia Transform, Ionian Sea, Greece, using seismological data and statistical methods. Our data include 29 events with M 〉 5.5 for the period 1636 - 2003. We found different recurrence behaviors for the Kefallinia Fault Zone （clustering and time-predictable recurrence behaviors） and the Letkada Fault Zone （near random and non-slip-predictable or non-time-predictable recurrence nature）. The different modes may be attributed to： （a） segment interaction along-strike （Kefallinia） by static triggering and （b） the influence of fault systems to the north and east on the recurrence on Lefkada. Within the active periods, earthquake recurrence intervals are distributed in a more dispersed fashion, and can be fitted well by a Weibull distribution. In contrast, the distribution of the quiet periods is relatively less dispersed and difficult to describe by suitable probability functions.
基金supported by the Director Foundation of Institute of Seismology,China Earthquake Administration(IS201326125)the National Natural Science Foundation of China(41204019,41304003)
文摘In this paper, the admittance function between seafloor undulations and vertical gravity gradient anomalies was derived. Based on this admittance function, the bathymetry model of 1 minute resolution was predicted from vertical gravity gradient anomalies and ship soundings in the experimental area from the northwest Pacific. The accuracy of the model is evaluated using ship soundings and existing models, including ETOPO1, GEBCO, DTU10 and V15.1 from SIO. The model＇s STD is 69. 481m, comparable with V15.1 which is generally believed to have the highest accuracy.
文摘As is well known, Greece has a significant number of earthquakes each year. Ιn recent years, several earthquakes have occurred in Greece. For this scope, a methodology was used to determine the source parameters. This methodology is based on minimizing the difference between the observed and the synthetic waveforms, using the method Source Parameters Calculation—SPCa <a href="#ref1" target="_blank">[1]</a>. The source parameters, using the proposed methodology, are calculated by comparing observed seismograms and synthetic by inverting data. The synthetics are calculated using the reflectivity method (Kennett, 1983) as implemented by Randall et al. (1994) for a given earth structure. This study includes inversion results for the strongest events that occurred in Greece from 2008 to 2014. For the same events calculated the main fault plane, using the method of Hypocenter Centroid-plot (HC-plot) <a href="#ref2" target="_blank">[2]</a> <a href="#ref3" target="_blank">[3]</a>. This methodology is a simple geometrical method based on the combination between the hypocentral position and the two possible fault planes.
基金Project supported by the National Natural Science Foundation of China and the Joint Earthquake Science Foundation
文摘The crustal structures of P velocity and density on the deep seismic sounding profile across the Dabieshan erogenic belt are presented. There is a 5-km-thick crustal "root" between the Yuexi and Xiaotian where the elevation is highest on the profile. An apparent Moho offset of 4.5 km beneath the Xiaotian-Mozitan fault marks the paleo-suture of the Triassic collision. A high-velocity anomaly zone at the depth below 3 km beneath the ultra-high pressure (UHP) zone may be correlated to the higher content of UHP metamorphic rocks.
文摘This study focuses on defining rates of fluvial incision for the last 580±5 kyr along valley systems of eight streams that drain the eastern part of the northern Peloponnese. The streams are developed on the uplifted block of the offshore-running Xylokastro normal fault, one of the main faults bounding the southern edge of the Gulf of Corinth half-graben, and have incised a set of ten uplifted marine terraces having an amphitheatric shape. These terraces range in age from 60±5 kyr to 580±5 kyr and have been mapped in detail and correlated with late Pleistocene oxygen-isotope stages of high sea-level stands by previous studies. The terraces were used in this paper as reference surfaces in order to define fluvial incision rates at the lower reaches of the studied streams. To evaluate incision rates, thirty-three topographic valley cross-sec- tions were drawn using fieldwork measurements as well as using a highly accurate （2×2 cell size） Digital Elevation Model （DEM） at specific locations where streams cut down the inner edges of the marine terraces. For each cross-section the ratio of valley floor width to valley height （Vf） and long-term mean stream incision rates were estimated for the last 580±5 kyr, while rock uplift rates were estimated for the last 330±5 kyr. The geomorphic evolution of the valleys on the uplifted block of the Xylokastro fault has been mainly driven by the lithology of the bedrock, sea level fluctuations during the late Quaternary, and incision of the channels due to the tectonic uplift. Stream incision rates range from 0.10±0.1 mm/yr for the last 123±7 kyr to 1.14±0.1 mm/yr for the last 310±5 kyr and are gradually greater from east to west depending on the distance from the trace of the fault.Downcutting rates are comparable with the rock uplift rates, which range from 0.4±0.02 mm/yr to 1.49±0.12 mm/yr, over the last 330±5 kyr.
文摘During August 1953 three strong earthquakes of magnitude ranging from 6.3 to 7.2 shook the Ionian Island of Cephalonia （Kefalonia）, Greece, and destroyed almost the entire building stock of the Island which consisted primarily of traditional unreinforced masonry （URM） houses. The authorities went on to restructuring of the building stock, using a structural system that is most like what is known today as confined masonry. They designed about 14 types of one- to two-storey buildings providing the engineers with detailed construction plans. These buildings are known as ＂Arogi＂ buildings （Arogi in Greek meaning Aid）. On the 24th of January and 3rd of February 2014, two earthquakes of magnitude 6.1 and 6.0 struck the island, causing significant soil damages, developing excessively high ground accelerations. Surprisingly, no damage was reported in the ＂Arogi＂ buildings. The seismic behavior of the buildings is examined by FEM linear analysis and it is compared to that of URM structures. Computed results illustrate that the displacements of identical URM buildings would be about twice the magnitudes observed in the corresponding ＂Arogi＂ ones, with the implication that the earthquake sequence of 2014 would have caused critical damage should the type of structure be of the URM type. Furthermore, it is illustrated that this low cost alternative method of construction is a very effective means of producing earthquake resilient structures, whereas further reduction of seismic displacement may be achieved in the order of 50% with commensurate effects on damage potential, when reinforced slabs are used to replace the timber roofs.
