Seismic Deformation Research Articles

The key role of conjugate fault system in importing earthquakes into the eastern flank of the Red Sea

This study aims to synthesize seismic observations with gravity and magnetic data and to suggest a new scenario on the development of the Harrat Lunayyir (HL) tectonic system on the eastern Red Sea coastline, Saudi Arabia. Gravity and aeromagnetic anomalies distinctly mapped the NE and NW trends, while the InSAR data depict a small NW–SE graben and an NW–SE dyke. High-resolution relocations, which are well-consistent with the focal mechanism solutions for events with magnitudes greater than 3.0, admit two distinctly fault styles of different orientations. Thus, leading to the NE and NW fault planes’ reactivation related to the Precambrian basement faults and the Red Sea rift system, respectively. The spatiotemporal distributions of epicenters and focal mechanism solutions suggest a new seismic deformation scenario of the 2009 earthquake seismic activity. The low static frictions of 0.2–0.35 obtained from the stress inversion indicates reactivation of preexisting faults in the respective seismogenic zones. The obtained results give rise to a swarm-like sequence of tectonic implications, two activated fault styles differently oriented, and an NE conjugate fault system inherited in the region, which plays a vital role in transferring the ambient stress regime into the Red Sea’s eastern flank.

Practical dynamic reliability analysis with spatiotemporal features in geotechnical engineering

ABSTRACT In recent years, improvements to the design of earth structures to ensure soil robustness against accidental disaster load conditions has gained considerable importance. In this paper, we propose a practical reliability analysis scheme that can enable the development of a robust design based on dimensionality reduction; this scheme employs input parameters, and it uses numerical analysis results as multidimensional information while preserving the spatiotemporal information to the maximum extent. Further, the proposed design scheme has practical design functions similar to those of conventional reliability analysis methods, such as the first-order second-moment method and first-order reliability method. Finally, the effectiveness of the proposed design scheme and its significant contribution to the practical design of earth structures are demonstrated via a time series seismic deformation analysis of simple embankments on liquefiable sand ground.

Analysis of Seismic Deformation from Global Three-Decade GNSS Displacements: Implications for a Three-Dimensional Earth GNSS Velocity Field

With the rapid development of Global Navigation Satellite System (GNSS) technology, the long-term accumulated GNSS observations of global reference stations have provided valuable data for geodesy and geodynamics studies since the 1990s. Acquiring the precise velocity of GNSS stations is very important for the study of global plate movement, crustal deformation, etc. However, the seismic activities nearby some GNSS observation stations may seriously change the station’s motion trajectory. Therefore, our research was motivated to propose a method allowing for station seismic deformation, and apply it to construct an updated global GNSS velocity field. The main contributions of this work included the following. Firstly, we improved the GNSS data processing procedures and seismic data selection strategies to obtain GNSS coordinate time series with mm-level precision (3–5 and 6–8 mm in the horizontal and vertical, respectively) and information of each site impacted by seismic events, which provides necessary input data for further analysis. Secondly, an Integrated Time Series Method (ITSM) concerning the effect of seismic deformation was proposed to model the station’s nonlinear motion accurately. Distinguished with existing studies, all parameters including seismic relaxation time can be simultaneously estimated by ITSM, which improves the accuracy and reliability of GNSS station velocity significantly. Thirdly, to optimize the ITSM-based model, the influences of seismic relaxation time (a. 0.1 × true, b. 10 × true, c. true), parameterization mode (a. Offset + Velocity, b. Offset + Velocity + PSD, c. Offset + Velocity + PSD + Period), and the Post-Seismic Deformation (PSD) model (a. None, b. Exp, c. Log, d. Exp + Log) on results of GNSS time series analyzing were discussed. The results showed that the fitting accuracy of GNSS displacements was better than 5 mm and 10 mm in the horizontal and vertical, respectively. Finally, the global GNSS station velocity field (referred to as GGV2020 hereafter) was refined by ITSM using global GNSS observations and seismic data during 1990–2020. This not only helps interpret plate tectonic motion, establish and maintain a Dynamic Terrestrial Reference Frame (DTRF) but also contributes to better investigating geodynamic processes. GGV2020 results showed that the accuracy of global velocity was better than 1 mm/a, and the averages of Root Mean Square Error (RMSE) were 0.19 mm/a, 0.19 mm/a, and 0.33 mm/a in the north, east, and up direction, respectively. Besides, the RMSE obeys normal distribution. Compared with ITRF2014, there was a difference of about 1–2 mm/a between them due to differences in terms of observation span, processing model, and geodetic technology. Moreover, GGV2020 is expected to enrich and update the existing velocity field products to describe the characteristics of regional crustal movement in more detail, especially in Antarctica.

Seismic and Geodetic Crustal Moment-Rates Comparison: New Insights on the Seismic Hazard of Egypt

A comparative analysis of geodetic versus seismic moment-rate estimations makes it possible to distinguish between seismic and aseismic deformation, define the style of deformation, and also to reveal potential seismic gaps. This analysis has been performed for Egypt where the present-day tectonics and seismicity result from the long-lasting interaction between the Nubian, Eurasian, and Arabian plates. The data used comprises all available geological and tectonic information, an updated Poissonian earthquake catalog (2200 B.C.–2020 A.D.) including historical and instrumental datasets, a focal-mechanism solutions catalog (1951–2019), and crustal geodetic strains from Global Navigation Satellite System (GNSS) data. The studied region was divided into ten (EG-01 to EG-10) crustal seismic sources based mainly on seismicity, focal mechanisms, and geodetic strain characteristics. The delimited seismic sources cover the Gulf of Aqaba–Dead Sea Transform Fault system, the Gulf of Suez–Red Sea Rift, besides some potential seismic active regions along the Nile River and its delta. For each seismic source, the estimation of seismic and geodetic moment-rates has been performed. Although the obtained results cannot be considered to be definitive, among the delimited sources, four of them (EG-05, EG-06, EG-08, and EG-10) are characterized by low seismic-geodetic moment-rate ratios (<20%), reflecting a prevailing aseismic behavior. Intermediate moment-rate ratios (from 20% to 60%) have been obtained in four additional zones (EG-01, EG-04, EG-07, and EG-09), evidencing how the seismicity accounts for a minor to a moderate fraction of the total deformational budget. In the other two sources (EG-02 and EG-03), high seismic-geodetic moment-rates ratios (>60%) have been observed, reflecting a fully seismic deformation.

Seismic and Energy Integrated Retrofitting of Existing Buildings with an Innovative ICF-Based System: Design Principles and Case Studies

This work proposes an innovative integrated retrofitting system aiming to improve both the seismic and energy performance of existing reinforced concrete and masonry buildings. The system is based on engineered insulating concrete form panels, installed on the outside of existing buildings as a shell exoskeleton. A key major advantage of the proposed system is that it addresses the contemporary improvement of seismic and energy performances of existing buildings in a single installation stage, operating exclusively from outside of the building. The insulating formworks are ad hoc prefabricated in a factory on the base of the specific geometry of the existing buildings so as to greatly maximize the ratio between overall retrofitting benefits and costs and at the same time to simplify the installation procedures. The objectives of the presented research are, on one hand, to highlight the major structural issues that the system aims to address, and on the other hand to illustrate the main characteristics and combined benefits of the proposed retrofitting system. From a structural point of view, the proposed system is conceived to behave as a non-dissipative structure with regard to seismic actions, and the lateral strength and stiffness of the structural elements are designed accordingly. An analytical design approach is proposed and validated using the available data from an experimental test performed on a full-scale simple building. Moreover, numerical modeling strategies for the proposed system are illustrated for two complex case study buildings. The results of the analyses show a considerable increase in lateral stiffness of the retrofitted buildings that, considering the non-dissipative behavior of the elements, leads to a relevant reduction of seismic deformation demand on existing structural elements.

Performance of steel moment-resisting frames in post-earthquake horizontally traveling fire

PurposeThe study investigates the performance of a three-story unprotected steel moment-resisting frame (SMRF) designed for high seismic demand in the fire-only (FO) and post-earthquake uniform and traveling fires (PEF). The primary objective is to investigate the effects of seismic residual deformation on the structure's performance in horizontally traveling fires. The traveling fire methodology, unlike conventional fire models, considers a spatially varying temperature environment.Design/methodology/approachMulti-step finite element simulations were carried out on undamaged and damaged frames to provide insight into the effects of the earthquake-initiated fires on the local and global behavior of SMRF. The earthquake simulations were conducted using nonlinear time history analysis, whereas the structure in the fire was investigated by sequential thermal-structural analysis procedure in ABAQUS. The frame was subjected to a suite of seven ground motions. In total, four horizontal traveling fire sizes were considered along with the Eurocode (EC) parametric fire for a comparison. The deformation history, axial force and moment variation in the critical beams and columns of affected compartments in the fire heating and cooling regimes were examined. The global structural performance in terms of inter-story drifts in FO and PEF scenarios was investigated.FindingsIt was observed that the larger traveling fires (25 and 48%) are more detrimental to the case study frame than the uniform EC parametric fire. Besides, no appreciable difference was observed in time and modes of failure of the structure in FO and PEF scenarios within the study's parameters.Originality/valueThe present study considers improved traveling fire methodology as an alternate design fire for the first time for the PEF performance of SMRF. The analysis results add to the much needed database on structures' performance in a wide range of fire scenarios.

Climate or tectonics? What controls the spatial-temporal variations in erosion rates across the Eastern Cordillera of Colombia?

Linking the long-term with the short-term exhumation history of a mountain range is vital for understanding the evolution of orogenic topography. Further, erosion rates could be controlled by the variability of climatic and/or tectonic processes over geological time. For example, in the Eastern Cordillera of the Colombian Andes, until recently climate forcing has been hypothesized as the primary driver of rapid Pliocene exhumation rates. In this contribution, we test this climate forcing hypothesis by integrating geomorphic, seismic, geological and published low-temperature thermochronological (Apatite Fission-Track; AFT), and cosmogenic nuclide (CN) data to quantitatively test the correlation of the spatial patterns of exhumation/erosion with either a tectonic or climatic forcing. From a regional perspective, both the long- and short-term erosion rates (derived from AFT and CN data, respectively) have a reasonable correlation with the seismic strain rates and local relief, whereas the contribution of the short-term rainfall patterns to exhumation (and denudation) is either weak or non-existent. For the Eastern Cordillera, tectonism through seismic deformation therefore seems to be a more critical driver of the topographic evolution of the range when compared with the climate variable. To deepen our investigation, we subdivided the study area into six subregions and performed a detailed statistical analysis. In one out of the six subregions (SEC2E), in the Quetame Massif area, short-term rainfall data is well correlated with the computed erosion rates. Nevertheless, the ten-fold difference between the long-term (2.36 km/Myr) and the current (0.27 km/Myr) denudation rates suggest they are strongly decoupled. The remaining five subregions featured varied correlations suggesting that the tectonic-climatic characteristics of each area must be considered and that effective local controls, such as rainfall in subzone SEC2E, cannot be extrapolated to the whole range. Finally, we discuss the tectonic implications of our findings, stressing how tectonic inheritance, typical of inversion orogens such as the Eastern Cordillera, is critical for understanding the spatial variability in exhumation/erosion rates and surface uplift. For instance, we reconstructed the paleoprofiles of four rivers (the Duda, Ariari, Guayuriba, and Guatiquía Rivers), draining the Sumapaz and Chingaza relict landscapes, on the hanging wall of the Servitá Fault, the typical example of an inverted structure. In this way, we evidenced a net surface uplift of at least 1.4 km since the late Miocene, which we speculate primarily controlled by the Servitá Fault. These findings have first-order implications as they provide evidence for Pliocene to Pleistocene landscape rejuvenation driven by tectonically inverted faults.

Present-day geodynamics of the Western Alps: new insights from earthquake mechanisms

Abstract. Due to the low to moderate seismicity of the European Western Alps, few focal mechanisms are available in this region to this day, and the corresponding current seismic stress and strain fields remain partly elusive. The development of dense seismic networks in past decades now provides a substantial number of seismic records in the 0–5 magnitude range. The corresponding data, while challenging to handle due to their amount and relative noise, represent a new opportunity to increase the spatial resolution of seismic deformation fields. The aim of this paper is to quantitatively assess the current seismic stress and strain fields within the Western Alps, from a probabilistic standpoint, using new seismotectonic data. The dataset comprises more than 30 000 earthquakes recorded by dense seismic networks between 1989 and 2013 and more than 2200 newly computed focal mechanisms in a consistent manner. The global distribution of P and T axis plunges confirms a majority of transcurrent focal mechanisms in the entire western Alpine realm, combined with pure extension localized in the core of the belt. We inverted this new set of focal mechanisms through several strategies, including a seismotectonic zoning scheme and grid procedure, revealing extensional axes oriented obliquely to the strike of the belt. The Bayesian inversion of this new dataset of focal mechanisms provides a probabilistic continuous map of the style of seismic deformation in the Western Alps. Extension is found to be clustered, instead of continuous, along the backbone of the belt. Robust indications for compression are only observed at the boundary between the Adriatic and Eurasian plates. Short-wavelength spatial variations of the seismic deformation are consistent with surface horizontal Global Navigation Satellite System (GNSS) measurements, as well as with deep lithospheric structures, thereby providing new elements with which to understand the current 3D dynamics of the belt. We interpret the ongoing seismotectonic and kinematic regimes as being controlled by the joint effects of far-field forces – imposed by the anticlockwise rotation of Adria with respect to Europe – and buoyancy forces in the core of the belt, which together explain the short-wavelength patches of extension and marginal compression overprinted on an overall transcurrent tectonic regime.

Crustal structure of the northern Andean Precordillera, Argentina, based on seismological and gravity data

This paper aims to better comprehend the crustal structure of the Precordillera and the Iglesia Valley. Located in the northern sector of the Pampean flat-slab (San Juan, Argentina), this region was the epicenter of the historical 1894, M > 7 earthquake (intensity IX on the modified Mercalli scale) and thus considered as a region of particularly high seismic hazard. The structure and deformation style associated with such events remain poorly understood.In this study, we analyze 4 months of regional seismic records from national and international stations in order to characterize a sequence of 74 crustal events that followed the occurrence of an intermediate magnitude (MW = 4.8 and ML = 5.2) earthquake on October 28th, 2019 for which we constrain the source parameters using regional moment tensor inversion.The analysis also includes the determination of 11 focal mechanisms from P-wave polarities and P–S waves amplitude ratios. Most of the focal mechanisms indicate reverse motion solutions.Seismological results are then integrated with other geophysics (gravity and seismic reflection profiles) as well as geological data, to build a 3D structural model that allows a better understanding of the crustal deformation mechanisms of the study area.Our results suggest that the seismic deformation is mostly concentrated in the basement of the Western Precordillera, at the transition with the Frontal Cordillera. This deformation seems respond to compressional stresses. The proposed model provides evidence of ongoing seismic activity related to the interaction between the thick-skinned deformation of the Frontal Cordillera with the thin-skinned fold and thrust belt of the Western Precordillera.

Seismic Deformations in an Early Christian Monastery in the Area of Djanavara, Varna, Bulgaria. Part 2: Results of Investigations

Seismic Deformations in an Early Christian Monastery in the Area of Djanavara, Varna, Bulgaria. Part 2: Results of Investigations

Approach to Evaluating Seismic Intensity by Integrating InSAR Co-seismic Deformation and Far Field Observation Data

Seismic intensity (SI) is an important reference index for understanding disaster situations, establishing emergency rescue plans and performing loss assessments after an earthquake. In this paper, we investigated the feasibility of assessing SI through interferometric synthetic aperture radar (InSAR) data after the Wenchuan earthquake on May 12, 2008, in China. The proposed approach relies on pre-existing residential data to obtain the regional seismic deformation corresponding to blocks. Theoretical maximum and minimum values analysis was carried out according to seismic attenuation relationships, and the deformation points were classified using Jenks natural breakpoints. The deformation field data were used to evaluate the epicenter and periphery areas. Instrument-based intensity values of stations were included in our analysis and used to investigate the periphery of the study area. Classification results of deformation field and instrument-based intensity values were combined to form a complete deformation field. The effectiveness of the method was verified based on a case study of the Yushu earthquake, another severe earthquake in China.The work represents one of the first attempts to establish the potential relationship between the seismic deformation field and intensity in China, validated against ground survey data. This study addresses methodological aspects, highlighting the potential of the co-seismic deformation field for intensity assessment, and discusses the limitations of terrain and data in this approach compared to ground surveys.

Genetic model for Jurassic shale-hosted Zn-Pb deposits of the Arak Mining District, Malayer-Esfahan metallogenic belt: Insight from sedimentological, textural, and stable isotope characteristics

The genetic model, including conditions under which mineralization formed, and relative timing of mineralization are critical questions for SEDEX (or shale-hosted massive sulfide, SHMS) deposits. There is increasing awareness that sub-seafloor replacement is an important process in the formation of some SEDEX deposits. We have studied the Hossein-Abad and Western Haft-Savaran Zn-Pb SEDEX deposits located in the Arak basin of the Malayer-Esfahan Metallogenic Belt, Iran, to address these questions of genesis. This metallotect formed in a back-arc paleotectonic setting as a result of the subduction of the Neo-Tethys oceanic plate beneath the Sanandaj-Sirjan Zone. The rocks that host the mineralization are Jurassic organic matter-bearing, fine-grained sandstones, siltstones, and shales. Asymmetric lenticular bedding, unidirectional flow (based on oblique silt lamination direction relative to horizontal bedding), graded bedding, and clay-rich interbeds indicate sediments were deposited from turbidity currents in a low-energy basin environment.There are three ore facies in the Hossein-Abad and Western Haft-Savaran Zn-Pb deposits: 1) bedded ore; 2) massive ore; 3) feeder zone. Bedded ore contains pyrite framboids and polyframboidal clusters. The size range of the pyrite framboids (3 to 6 µm in diameter) indicates they formed in the water column and not in the subsurface. Characteristic structures in bedded ore are: 1) sulfide-bearing silt injections into clay-filled burrows, 2) injection of sulfide-bearing silt into flame structures of claystone laminae, and 3) organic matter in claystone oriented obliquely relative to bedding. These structures are the result of seismic deformation induced by synsedimentary earthquakes, whereby sulfides that formed in permeable unconsolidated sediment were injected into the organic matter-bearing claystone unit.The δ18O and δ13C values of siderite, calcite and dolomite in veins from the feeder zone and massive ore range from 12.2 to 23.8‰ and −16.7 to 1.7‰, respectively. These values indicate that formational water, seawater and organic matter oxidation-decomposition all played a role in hydrothermal carbonate formation. Melting and homogenization temperatures for CO2 for CO2-bearing fluid inclusions range from −57.5 to −60 °C and 6.6 to 29.5 °C, respectively, and indicate the presence of < 15 mol percent CH4. The CO2 homogenization temperature range suggests the CO2-rich phase is a CO2-CH4 mixture. The CH4 and CO2 in the H2S-bearing fluid were likely generated by biodegradation and oxidation of organic matter via BSR and methanogenesis.The sulfur isotope compositions of pyrite, galena, sphalerite and chalcopyrite from the feeder zone and the massive ores range from δ34S −4.3 to + 7.2‰ and display equilibrium fractionations, indicating that the sulfur originated from two processes: (a) bacterial reduction of seawater sulfate (BSR) (distal from mineralization site), and (b) thermochemical reduction of seawater sulfate (TSR) (in both massive ore and feeder zone). Sulfur isotope geothermometric calculations (Δgalena-sphalerite) for two samples give temperatures in the range 209–224 °C for the massive ore facies. Such high temperatures negate a contribution of sulfur from BSR. However, BSR likely occurred in sediments distal to the feeder zone, where seawater sulfate was bacterially reduced to H2S, and this H2S migrated to the mineralization site during diagenesis. Collectively, the stable isotope data indicate mineralization formed in response to mixing occurred between ascending hot metalliferous hydrothermal fluid that rose up the fault and fracture network, with H2S-bearing fluid and sulfate-bearing percolating seawater, triggering sulfide deposition.

Exploring the relationship between InSAR coseismic deformation and earthquake-damaged buildings

Strong ground vibration triggered by seismic waves is one of the most significant factors that causes building damage during a seismic event. The interferometric synthetic aperture radar (InSAR) technique can efficiently and quickly provide seismic deformation information. There is no clear relationship model between seismic deformation and the degree of building damage.Considering the earthquake that hit Wenchuan (China) on May 12, 2008, in this work, a method to evaluate the degree of building damage based on coseismic deformation is presented. Based on 51 building area samples selected, taking the Deformation normalization index(DNI) as the independent variable and the earthquake damage index (EDI) of the field survey data provided by the China Earthquake Administration (CEA) as the dependent variable, the relationships between seismic damage survey data and the seismic deformation of adobe structures, brick-wood structures, brick-concrete structures and reinforced concrete frame structures are analysed. There are linear relationships between the normalized deformation indices of adobe and brick-concrete structure types and the EDIs of buildings. There are quadratic relationships between the normalized seismic deformation indices of brick-wood structures and reinforced concrete frame construction types and the EDIs of buildings. Additionally, the regional curve estimates of the comprehensive building damage index and the normalized index of seismic deformation show that there is a quadratic relationship between the comprehensive building damage index and the normalized index of seismic deformation. The validity of the modelling method was verified by data from the Yushu earthquake in 2010. The results can provide an accurate and reliable reference basis for post-earthquake rescue and decision making.The work represents a new concept and method for the rapid assessment of building damage data from the perspective of surface deformation movement by addressing methodological steps, highlighting the potential of using the coseismic deformation field obtained during building damage assessment, and discussing the potential and limitations of InSAR technology in the field of damage detection.

A BOUNDARY FORCED RESPONSE DISPLACEMENT METHOD FOR SEISMIC ANALYSIS OF SYMMETRICAL UNDERGROUND STRUCTURES

A boundary forced response displacement method is proposed for the seismic analysis of symmetrical underground structures based on the requirement of quasi-static pushover test of soil-underground structure systems. The implementation procedure and special features of the method are introduced in detail. We took the Daikai subway station which was damaged during the Kobe earthquake in Japan as an example for the analysis, and compared the results of boundary forced response displacement method, the FEM seismic deformation method and the dynamic time-history analysis method. The results show that the accuracy of the new method was much higher than the FEM seismic deformation method when the width of the model was reasonable. The errors of the internal forces and the story drift were less than 15%. The new method is an effective simplified method for seismic response analysis of symmetrical underground structures. The attenuation law of lateral boundary forced displacement was analyzed. It provides references for the quasi-static pushover test of soil-underground structure system.

Seismic Deformations in an Early Christian Monastery in the Area of Djanavara, Varna, Bulgaria. Part 1: Study Methods

Seismic Deformations in an Early Christian Monastery in the Area of Djanavara, Varna, Bulgaria. Part 1: Study Methods

Seismic deformation styles in the upper and lower plate domains of the Calabrian subduction zone, south Italy

We analyzed waveform inversion focal mechanisms of earthquakes that occurred in the last decades in the Calabrian Arc region, the most seismic area of Italy according to historical catalogs and the only where active subduction can be still found along the Nubia-Eurasia convergent margin. We focused our analysis on earthquakes shallower than 40 km and, in order to reduce the effects of very local scale processes, with magnitude 4.0 and larger. Hypocenters of the individual earthquakes with their uncertainties have been compared with location and geometry of the Calabrian Subduction Interface (CSI), reconstructed by previous investigators, with the purpose of associating the individual earthquakes and their focal mechanisms to the shallower part of the Ionian subducting plate (lower plate) or to the Tyrrhenian overriding plate (upper plate). By integrating focal mechanisms available from literature and catalogs with those properly estimated in this study we obtained a dataset of 31 focal mechanism solutions. Considering the focal depth of each earthquake and the CSI depth in the relative epicentral area, only one of the selected earthquakes could not be univocally associated to one of the two domains (lower or upper plate). The other 30 FMs show an evident west-east separation between the western earthquakes of the Tyrrhenian Sea and mainland Calabria occurring in the upper plate domain (17 earthquakes), and the eastern ones of the Calabria Ionian shore and relative offshore occurring in the lower plate domain (13 earthquakes). The focal mechanism distribution highlights clear extension in the Tyrrhenian overriding plate with opening direction trending roughly perpendicular to the Calabrian Arc mountain chain. The situation appears quite more complex in the Ionian lower plate where seismic faulting indicates marked heterogeneity with prevailing compressional features. These results are discussed together with the information available in the literature for the study area concerning historical earthquakes and relative sources, tectonic stress distributions, geodetic crustal velocities and related strain rates. Finally, we comment our findings in the light of recent geodynamic models proposed in the literature for the same area and for the wider central Mediterranean region.

Experimental study on the seismic deformations of rockfill breakwaters

Breakwaters protect ports from high waves and hydraulic related phenomena. However, their seismic performance is of paramount importance in earthquake-prone areas. This study examined the seismic behavior and deformation of rockfill breakwaters with the use of shaking table modeling. As a part of performance base design, the scaled model tests were performed based on breakwaters of South Pars Petrochemical Port (SPPP), south Iran. The results indicate that, along with shear deformation, volumetric strain plays a major role in the deformation and settlement of breakwaters. Sections that were protected by armor exhibited better stability and performance. For SPPP breakwater a limited settlement was a strict performance criterion to allow installation of a pipeline on its crest. It was observed that densifying the upper part of breakwater did not control the settlement particularly when the core was made up of fine-grained material. The seismic performance of the pile-breakwater system also has been examined using scale-model tests. The results showed that the pile bearing system exhibited good performance in preventing the settlement of the pipelines running along the crest of the breakwater. However, it was shown that the pile bearing system did not provide sufficient control for lateral displacement and an isolation system would be necessary.

An Improved Quadtree Sampling Method for InSAR Seismic Deformation Inversion

With the development of interferometric synthetic aperture radar (InSAR), the seismic deformation observation density increases sharply. Data down-sampling can effectively reduce the observation density and the computational cost for subsequent researches. Considering the saliency of the deformation field, we introduce a saliency-based quadtree algorithm for down-sampling (SQS). Three simulation experiments show that SQS can effectively distinguish the near-field and far-field deformation, as well as reduce the amount of observation, while keeping the detailed information of the main deformation near the fault. SQS can avoid the interference of far-field local deformation better than the traditional quadtree sampling algorithm (QS), thus obtaining better inversion results. We took the Dingri earthquake on 20 March 2020 as a case study to verify the advantages of SQS in dealing with real earthquake deformation. We obtained the co-seismic deformation from the ascending and descending Sentinel-1 for the Dingri earthquake, using QS and SQS for sampling and inversion separately. The results show the advantages of SQS in data volume reduction, observation distribution, anti-interference of local deformation, and inversion accuracy. Our preferred solution based on SQS shows that the Dingri earthquake was caused by a normal fault slip. The main slip area is 2–5.5 km deep with a maximum slip of 0.68 m. The estimated geodetic moment is 3.14 × 1017 Nm, corresponding to a magnitude of Mw5.63.

Semibrittle seismic deformation in high-temperature mantle mylonite shear zone along the Romanche transform fault.

Oceanic transform faults, a key element of plate tectonics, represent the first-order discontinuities along mid-ocean ridges, host large earthquakes, and induce extreme thermal gradients in lithosphere. However, the thermal structure along transform faults and its effects on earthquake generation are poorly understood. Here we report the presence of a 10- to 15-kilometer-thick in-depth band of microseismicity in 10 to 34 kilometer depth range associated with a high-temperature (700° to 900°C) mantle below the brittle lithosphere along the Romanche mega transform fault in the equatorial Atlantic Ocean. The occurrence of the shallow 2016 moment magnitude 7.1 supershear rupture earthquake and these deep microearthquakes indicate that although large earthquakes occur in the upper brittle lithosphere, a substantial amount of deformation is accommodated in the semibrittle mylonitic mantle that resides at depths below the 600°C isotherm. We also observe a rapid westward deepening of this band of seismicity indicating a strong lateral heterogeneity.

Seismic responses of hyperbolic cooling towers under horizontal and vertical earthquake

Following the dynamic property analysis and elaboration, linear response spectrum analysis (RSA) and response history analysis (RHA) were conducted on a representative hyperbolic cooling towers (HCT) in present study. The seismic responses in tower shell were illustrated in detail, including the internal force amplitude, modal contribution, influence from damping ratio, comparison of results got from RSA and RHA and especially the latitude distributions of internal forces. The results show that the eigenmodes could be classified in a new method into four types according to their mode shapes and only the lateral bending modes and vertical stretching modes are meaningful for horizontal and vertical earthquake correspondingly. The bending modes and seismic deformation display the same feature which is global lateral bending accompanied by minute circular flow displacement of section. This feature also decides the latitude distributions of internal forces as sine or cosine. Moreover, the following method is also proposed for approximate estimation of internal force amplitudes without time-consuming response history analysis: getting the response spectrums of the selected ground accelerations and then comparing values of response spectrums at the natural period of first lateral bending mode because it is always prime dominant for horizontal seismic responses.