Temporal and spatial variations of seismicity scaling behavior in Southern México

R/S analysis is used in this work to investigate the fractal correlations in terms of the Hurst exponent for the 1998–2011 seismicity data in Southern Mexico. This region is the most seismically active area in Mexico, where epicenters for severe earthquakes (e.g., September 19, 1985, M_w = 8.1) causing extensive damage in highly populated areas have been located. By only considering the seismic events that meet the Gutenberg–Ritcher law completeness requirement (b = 0.97, M_GR = 3.6), we found time clustering for scales of about 100 and 135 events. In both cases, a cyclic behavior with dominant spectral components at about one cycle per year is revealed. It is argued that such a one-year cycle could be related to tidal effects in the Pacific coast. Interestingly, it is also found that high-magnitude events (M_w ≥ 6.0) are more likely to occur under increased interevent correlations with Hurst exponent values H > 0.65. This suggests that major earthquakes can occur when the tectonic stress accumulates in preferential directions. In contrast, the high-magnitude seismic risk is reduced when stresses are uniformly distributed in the tectonic shell. Such cointegration between correlations (i.e., Hurst exponent) and macroseismicity is confirmed for spatial variations of the Hurst exponent. In this way, we found that, using the Hurst exponent standpoint, the former presumed Michoacan and the Guerrero seismic gaps are the riskiest seismic zones. To test this empirical finding, two Southern Mexico local regions with large earthquakes were considered. These are the Atoyac de Alvarez, Guerrero (M_w = 6.3), and Union Hidalgo, Oaxaca (M_w = 6.6), events. In addition, we used the Loma Prieta, California, earthquake (October 17, 1989, M_w = 6.9) to show that the high-magnitude earthquakes in the San Andreas Fault region can also be linked to the increments of determinism (quantified in terms of the Hurst exponent) displayed by the stochastic dynamics of the interevent period time series. The results revealed that the analysis of seismic activity by means of R/S analysis could provide further insights in the advent of major earthquakes.     

Geochemical Monitoring of Geothermal Waters (2002–2004) along the North Anatolian Fault Zone, Turkey: Spatial and Temporal Variations and Relationship to Seismic Activity

A total of nine geothermal fields located along an 800-km long E-W transect of the North Anatolian Fault Zone (NAFZ), Turkey were monitored for three years (2002–2004 inclusive; 3-sampling periods per year) to investigate any possible relationship between seismic activity and temporal variations in the chemistry and isotope characteristics of waters in the fields. The geothermal fields monitored in the study were, from west to east, Yalova, Efteni, Bolu, Mudurnu, Seben, Kur?unlu-Çank?r?, Hamamözü, Gözlek and Re?adiye. The chemical (major anion-cation contents) and isotopic (¹⁸O/¹⁶O, D/H, ³H) compositions of hot and cold waters of the geothermal sites were determined in order to both characterize the chemical nature of the individual fields and identify possible temporal variations associated with localized seismic activity. The geothermal waters associated with the NAFZ are dominantly Na-HCO₃, whereas the cold waters are of the Ca-HCO₃ type. The oxygen- and hydrogen-isotope compositions reveal that the hot waters are meteoric in origin as are their cold water counterparts. However, the lower δ¹⁸O, δD and ³H contents of the hot waters point to the fact that they are older than the cold waters, and that their host aquifers are recharged from higher altitudes with virtually no input from recent (post-bomb) precipitation. Although no major earthquakes (e.g., with M ≥ 5) were recorded along the NAFZ during the course of the monitoring period, variations in the chemical and isotopic compositions of some waters were observed. Indeed, the timing of the chemical/isotopic changes seems to correlate with the occurrence of seismic activity of moderate magnitude (3 < M < 5) close to the sampling sites. In this respect, Cl, ³H and Ca seem to be the most sensitive tracers of seismically-induced crustal perturbations, and the Yalova and Efteni fields appear to be the key localities where the effects of seismic activity on the geothermal fluids are most pronounced over the monitoring period. The present study has produced a ‘baseline’ database for future studies directed at characterizing the effects of moderate-major earthquakes on the composition of geothermal waters along the NAFZ. Future work involving longer monitoring periods with more frequent sampling intervals should lead to a better understanding of the underlying mechanism(s) producing the observed chemical and isotopic variations.     

Discussion of the Horizontal Intensity of Late Quaternary Fault Activity Along the Tianjingshan Fault Zone in Different Time Intervals and Fault Segments

By computing and classifying the data of gully offset obtained from field surveys along the Tianjingshan fault zone and estimating the ages of three types of gullies,the strike-slip rates along the fault zone are discussed in different time intervals and fault segments.The results suggest that the intensity of activity along the fault zone is not strong,but the differences between different time intervals and fault segments since the late Pleistocene have been obvious.The average rates range from 0.23 mm/a to 1.62 mm/a.The largest average rate is 1.40 mm/a,which occurred in the early and middle of late Pleistocene along the western segment of the fault zone.Since the late stage of the late Pleistocene,the center of faulting activity of the fault zone has shifted to the middle segment,and the average slip rates range have changed from 1.30 mm/a to 1.63 mm/a.     

The North Nuratau Fault Zone,Uzbekistan—Structure and evolution of a Palaeozoic Suture Zone

The Nuratau Fault Zone in eastern Uzbekistan forms part of the western prolongation of the Tien Shan, an extensive orogenic zone located along the margin of the Central Asian Orogenic Belt. The Nuratau region is geologically complex, forming part of the suture zone between the Kazakh-Kyrgyz continent and the Alai microcontinent. A model is proposed suggesting modified N-directed subduction model, where an extensive fold-and-thrust belt developed in the Nuratau region. This, coupled with significant transform activity would have resulted in major segmentation of the existing stratigraphy in the region, as well as the development of a foredeep basin to the north of the fold-and-thrust belt. Regional suturing and collision was variable. Indeed, the collisional history probably involved multi-phase subduction/accretion of various microcontinents, ancient island arcs, and fragments of oceanic islands. Final collision would have produced an eroding basinal high in the region of the Nuratau mountains, which issued sediment both northwards into the remnant basin of the Turkestan Ocean, but also to the south into the newly forming Amu Darya Basin.     

Active Feature of the Ganzi-Yushu Fault Zone in the Late Quaternary

Based on regional geological mapping results and interpretation of satellites images and areophotos in combination with detailed field study,this paper gives the spatial distribution of recent surface activity of the Ganzi-Yushu fault zone(GYF).According to faulted landform as well as deformation and displacement of young deposit layers,the slip rates of GYF since the late Quaternary are briefly studied,combined with the results of geological chronology(14C and Thermoluminescene dating).The result shows that the average slip rates of GYF is differentiate along different segments:Ganzi segment:horizontal rate is 3.4±0.3 mm/a,vertical rate is 2.2±0.1 mm/a;Manigange segment:horizontal rate is 7.0±0.7 mm/a;Denke segment:horizontal rate is 7.2±1.2 mm/a;Dangjiang segment:horizontal rate is 7.3±0.6 mm/a.     

Activity Feature of Kazkeaerte Fault Zone in the Late Quaternary

ＩＮＴＲＯＤＵＣＴＩＯＮＫａｚｋｅａｅｒｔｅｆａｕｌｔｚｏｎｅａｂｏｕｔ 1 0 0ｋｉｌｏｍｅｔｅｒｓｌｏｎｇ (Ｆｉｇ .1 ) ,ｉｓｔｈｅｅａｓｔｅｒｎｌｉｍｂｏｆｔｈｅｌａｔｅｓｔｄｅｆｏｒ ｍａｔｉｏｎｂｅｌｔｏｆｔｈｅｎｏｒｔｈｅｒｎｍａｒｇｉｎｏｆＰａｍｉｒｓ (ＣｈｅｎＪｉｅ ,ｅｔａｌ,1 997) .Ｍａｎｙｍｏｄｅｒａｔｅｌｙｓｔｒｏｎｇｅａｒｔｈ ｑｕａｋｅｓｏｃｃｕｒｒｅｄａｌｏｎｇｔｈｉｓｚｏｎｅ (ＦｅｎｇＸｉａｎｙｕｅ ,ｅｔａｌ,1 987) .ＴｈｅｌａｔｅＱｕａｔｅｒｎａｒｙｄｅｆｏｒｍａｔｉｏｎ…     

A statistic of water mass intrusions in the south Indian Ocean between 100° E and 110° E

Ocean Dynamics - The concept of water type richness wtr and inversion count inv is introduced and applied to high-resolution Argo float data in a meridional strip in the southern Indian Ocean as a...     

A model of seismicity with fractal structures and a preliminary discussion on the relation between D and b value

ＡｍｏｄｅｌｏｆｓｅｉｓｍｉｃｉｔｙｗｉｔｈｆｒａｃｔａｌｓｔｒｕｃｔｕｒｅｓａｎｄａｐｒｅｌｉｍｉｎａｒｙｄｉｓｃｕｓｓｉｏｎｏｎｔｈｅｒｅｌａｔｉｏｂｅｔｗｅｅｎＤａｎｄｂｖａｌｕｅＨａｔ－ＫｕｎＪＩＡＮＧ（蒋海昆）ａｎｄＳｈｏｕ－ＺｈｏｎｇＤＩ...     

The Geothermal Study of the Mid-Segment of the Tancheng-Lujiang Fault Zone and Its Neighboring Region

In this paper,25 new terrestrial heat flow values newly observed along the mid-segment of the Tancheng-Lujiang fault zone are listed.With these geothermal data and 37 other terrestrial heat flow values(previously published),we describe the distribution features of terrestrial heat flows in the area.In this research,the two-dimensional temperature structure from the surface to lithospheric bottom of the Huaibei-Sixian-Jinhu profile is inferred by using the finite-element method and the temperature and heat flow of sedimentary,granitic,and basaltic layers is calculated.     

The Fractal Feature of Granulometric Composition in Fault Gouges from the Yishu Fault Zone and Adjacent Northwest-Trending Faults and Its Seismo-geological Implications

In this work,the fractal dimension of granulometric composition in the fault gouge from the Yishu fault zone and northwest-trending faults on its west side is calculated and studied based on the fractal theory of rock fragmentation.The seismo-geological implications of the fractal dimension of granulometric composition in fault gouges are also discussed.The results show that the Yishu fault zone is more active than the northwest-trending faults and the Anqiu-Juxian fault is the most active in the Yishu fault zone.The fractal dimension of fault gouge is a parameter describing the relative active age and rupture mode of the fault and forming age of the fault gouge.The fractal dimension value is also related to the parent rock,thickness,structural position,and clay content of the fault gouge.     

Pull-apart Basins and the Total Lateral Displacement Along the Haiyuan Fault Zone in Cenozoic

ＩＮＴＲＯＤＵＣＴＩＯＮＩｔｉｓｄｅｂａｔｅｄａｂｏｕｔｔｈｅｔｏｔａｌｌａｔｅｒａｌｄｉｓｐｌａｃｅｍｅｎｔａｌｏｎｇｔｈｅｍａｉｎｂｏｕｎｄａｒｙｆａｕｌｔｓｏｆｉｎｔｒａｐｌａｔｅｂｌｏｃｋｓｉｎｅａｓｔｅｒｎＡｓｉａｃｏｎｔｉｎｅｎｔｉｎＣｅｎｏｚｏｉｃｅｒａ .Ｉｎｔｈｅ 1 970ｓｏｆ2 0ｔｈｃｅｎｔｕｒｙ ,ｓｏｍｅｓｃｉｅｎｔｉｓｔｓｈａｄｅｓ ｔｉｍａｔｅｄｌａｔｅｒａｌｄｉｓｐｌａｃｅｍｅｎｔｂａｓｅｄｏｎｇｅｏｍｏｒｐｈｉｃｄａｔａ .Ｔｈｅｙｐｒｏｐｏｓｅｄｔｈａｔｔｈｅｔｏｔａｌｄ…     

Interannual variations in salt flux at 80°E section of the equatorial Indian Ocean

The interannual variations in salt flux on the 80°E section in the equatorial Indian Ocean were explored based on the ORAS5 data, which was quite consistent with the observational data among the four available reanalysis datasets. The results indicated that the area with significant interannual variations in salt flux coincided with that of significant climatological mean salt flux in general and was mainly located in the upper 150 m layer. Specifically, three important areas were identified in ...     

Characteristics of Late Quaternary Activity of the Gadê Segment in the Madoi-Gadê Fault Zone

Madoi-Gadê fault is an active fault in the Bayan Har block.According to field investigation,there is an earthquake surface rupture fairly well preserved on the Gadê segment of the Madoi-Gadê fault zone.The length of the rupture is approximately 50km,with a general strike of NW.The maximum horizontal sinistral displacement is about 7.6m and the maximum vertical displacement is about 4m.A large number of earthquake traces are to be found along the rupture zone,and the phenomena on the surface rupture are also...     

Features of fractal dimension anomaly of radon content in underground water in North China before and after the 1976 Tangshan earthquake

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Structure and development of the Andean system between 36° and 39°S

One of the main morphological changes along the Southern Central Andes occurs from 36° to 39°S. The northern portion is characterized by prominent basement structures and a thick-skinned orogenic front with relief of over 2000 m with a deep level of exhumation where more than 4 km of section has been eroded. Contrastingly, the southern part is formed by mildly inverted basement structures restricted mainly to the hinterland zone, which reaches only 1500–1700 m relief. We quantify the variable contributions of two main contractional stages through the construction of three regionally balanced sections across the Andes, constrained by field and geophysical data. Extensional re-activation described for this segment in late Oligocene-early Miocene and Pliocene to Quaternary times, after the two main contractional episodes, suggests only 3 km of stretching that represents 30–10% of the original longitude. We, therefore, conclude that while initial Late Cretaceous to Eocene compression was similar along strike (∼10–7 km), it is the contrasting degrees of Neogene shortening (∼16–6 km) that have played the largest role in the along strike differences in structure and morphology along this portion of the southern Andes. Variable Neogene arc expansion could be responsible for the contrasting contractional deformation: In the north, late Miocene arc-related rocks cover most of the retroarc zone (>200 km with respect to the late Miocene arc front in the south), presumably driven by a shallow subduction episode in the area, whereas to the south they remain restricted to the continental drainage divide. Other factors involving architecture of previous rift structures, are proposed as additional mechanisms that accommodated variable shortening magnitudes through inversion.     

The Microstructural Characteristics of Fault Rocks from the Wasatch Fault Zone in Utah (USA) Under Polarizing and Electronic Microscope and Its Seismogeologic Significance

The microstructures of fault rocks from the Wasatch fault zone in Utah (USA) have been studied using a polarizing microscope,a scanning electron microscope (SEM) and an ultrahigh-voltage electron microscope (HVHM).This fault zone may be recognized as one a with long history of seismic activity according to the microstructural characteristics such as type, deformation characteristics,melting structure and surface textures of the fault rocks.However,the main fault now present seems not to have been noticeably active since the late Pleistocene (Q_3),as shown by the eroded-surface texture on the quartz fragments in the fault gouge.Meanwhile,those faults supposed to be strongly active in modern times are branching faults much closer to the basin side and are covered by the Holocene sediments in the basin.     

The behavior of seasonal variations in induced seismicity in the Koyna–Warna region,western India

Based on the earthquake catalog data for the Koyna–Warna region of induced seismicity in western India, the seasonal variations in seismic activity associated with annual fluctuations in the reservoir water level are analyzed over the time span of the entire history of seismological observations in this region. The regularities in the time changes in the structure of seasonal variations are revealed. The seasonal seismic activity is minimal in May–June when the reservoir level is lowest. During the remaining part of the year, the activity has three peaks: the fall peak in September, winter peak in November–December, and spring peak in February–March. The first mentioned peak, which falls in the phase of the water level reaching its maximal seasonal value is considered as the immediate response of the fluid saturated medium to the additional loading under the weight of reservoir water. The two subsequent maxima concur with the decline phase in the reservoir level and are interpreted as the delayed response associated with the changes in the properties of the medium due to water diffusion. It is shown that the intensities of the immediate and delayed responses to the seasonal water level variations both vary with time as does their ratio. The probable factors affecting the variations in the intensity of the seasonal components of the reservoir-induced seismicity are discussed.     

Effects of lunar-solar tides in the variations of geophysical fields at the boundary between the Earth’s crust and the atmosphere

Extraterrestrial forcing of natural environmental processes by gravitational interaction between the Sun, the Moon, and the Earth is considered. Based on the instrumental data, the main periodical components and cycles are identified in the time variations of some geophysical fields at the boundary between the Earth’s crust and the atmosphere. Correlation analysis shows that the lunar-solar tides are the key factor responsible for diurnal and quasi-biweekly variations in the ground electric field, radon emanation, water level in wells, and microseismic vibrations. The tidal influence on the various-scale movements of the blocks of the Earth’s crust is analyzed. In the context of the vertical, lateral, and rotational motion of crustal blocks, which is very important for the platforms, a new, precession-like type of displacements is revealed. These movements develop as a result of the nonsynchronous tidal responses of the block and the adjacent interblock gaps or tectonic structures whose strength and strain properties are different in different directions.     

A Preliminary Study on the New Activity Features of the Lajishan Mountain Fault Zone in Qinghai Province

INTRODUCTIONThe Lajishan Mountainlies onthe northeastern margin of Qinghai_Xizang(Tibet)plateau.It is ageomorphic gradient zone,separatingthe hinterland of Tibetfromthe Loess plateau.The Lajishanfaultis a product of Caledonian movement,havingexperienced m…