Seismic Investigations Research Articles

Incremental Dynamic Analysis for Estimating Seismic Performance of Multi-Story Buildings with Butterfly-Shaped Structural Dampers

Structural strength and stiffness were previously investigated to sufficiently improve the lateral load resistance against major events. Many buildings require appropriate design to effectively withstand the lateral seismic loads and reduce the corresponding damages. Design methodologies and structural elements were recently introduced to improve the energy dissipation capability and limit the high force demands under seismic loadings. The new systems are designed to protect the structural integrity and concentrate the inelasticity in a specific area, while the remaining parts are kept undamaged and intact. This study introduces a new structural system with dampers having strategic cutouts, leaving butterfly-shaped shear dampers for dominating the yielding mechanism over other brittle limit states. The new system is designed for re-establishing the conventional eccentrically braced frame system with simple linking beams. The system with strategic cutouts is subsequently used and compared with the eccentrically braced frames (EBF) system for seismic performance investigation and incremental dynamic analysis (IDA), using the OpenSees program, which is used to indicate the collapse behavior under forty-four selected ground motions. Results show that the butterfly-shaped multi-story buildings, compared to the corresponding conventional systems, are capable of enhancing the system resistance against lateral seismic loads by postponing the collapse state to the larger drift ratio values.

Seismic near-surface investigations at the InSight landing site using the Heat and Physical properties (HP3) probe as a seismic source

Seismic near-surface investigations at the InSight landing site using the Heat and Physical properties (HP3) probe as a seismic source

Evidence of sea level drawdown at the end of the Messinian salinity crisis and seismic investigation of the Nahr Menashe unit in the northern Levant Basin, offshore Lebanon

AbstractSeveral important aspects of the Messinian salinity crisis (MSC) are still subject to controversy and debate after more than 40 years of studies. Recent work from the eastern Mediterranean have provided a renewed stratigraphic framework for the basin that is inconsistent with previous interpretation studies in the area. This study presents a description of the evolution of the depositional environment in the northern Levant Basin in a time interval surrounding the end of the famous event, from Late Messinian to the Pliocene. Through seismic mapping, we have identified a sediment package overlying the intra‐Messinian truncation surface (IMTS). This package is interpreted as an axial fluvial system running along the Levant Margin in stage 3 of the salinity crisis, likely composed of redeposited evaporites and clastic material. The system was fed primarily from a large fan system building out from the basin margin during a time of sea‐level low stand following a major erosional event, and presumably also from similar systems along the Latakia Ridge and Syria. Our interpretation also lends weight to the theory of a subaerial origin for the truncation surface after a catastrophic desiccation event succeeding the deposition of the halite‐dominated Messinian evaporite succession, based on differences in maximum erosional depth throughout the basin. After the deposition of the post‐IMTS package, deep marine settings were restored in the basin, and hemipelagic sediments from the Nile Delta and the Levant Margin have dominated the sediment deposition since.

Shallow Seismic Reflection Investigation of Unstable Sedimentary Deposits in the Dăneasa Area, Romania

Results of shallow seismic reflection measurements, performed over an area with unstable sedimentary formations in the near subsurface, are presented. The investigated area is located on the Olt Valley, in the vicinity of the Dăneasa village, Romania, crossed by a railway line and a national road on which the traffic is very intense. Data were collected along a linear profile, with a length of 94 m, perpendicular to the railway line and the national road using a fixed spread of 48 vertical-component geophones with the sources rolling along the acquisition line. The surface waves generated by the intense traffic on the national road interfered with the seismic arrivals seen on most of shot gathers, especially with those seen on the traces from receiver locations greater than 48 m. The interrupted continuity of two shallow reflectors, R1 and R2, seen on the depth-converted seismic section at depth values shallower than 30 m, could be interpreted as an effect of the presence of two steep failure planes deveIoped into the ground. A P-wave velocity-depth model down to a depth of 20 m after first-arrival traveltime tomography was then created, on which four sedimentary layers with variable thicknesses and constant velocities, separated by the interfaces L1, L2 and L3, were interpreted. By comparing the depth-converted seismic section with the P-wave velocity-depth model, the reflectors R1 and R2 on the seismic section correspond pretty well with the interfaces L2 and L3 from the velocity-depth model.

Image and Data Processing for InSight Lander Operations and Science

The Instrument Site Selection and deployment for the upcoming Mars InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) Lander is highly dependent on image products, particularly mosaics, created from the Instrument Deployment Camera (IDC) and Instrument Context Camera (ICC). When data are downlinked, the Multimission Image Processing Lab (MIPL) at JPL will process image and instrument data to aid in the deployment and monitoring of these instruments. MIPL’s functions include raw telemetry processing, stereo correlation, mosaic generation, terrain mesh generation, radiometric correction, pointing correction (bundle adjustment), and the creation of products such as instrument deployment maps, surface normal products, slope products, XYZ point clouds, and roughness map layers. A software pipeline performs systematic, automated execution of the programs that create these products on every image and stereo pair received, while the pointing correction and most mosaics are hand-generated by the MIPL team members for testing and surface operations. Several mission operations software packages are used to view, query, and analyze the processed images and mosaics for placing the main science instruments for the mission.

Migration of duplex waves for coal-bed methane prediction

A case study of using migration of duplex waves to trace zones of near-vertical fracturing in coal formation is described. As a rule, coal-bed methane traps are connected with these zones, however, identification and tracing of them based on the standard seismic exploration techniques are practically impossible. It is shown that the joint analysis of structural interpretation and seismic facies investigation data and of the results of duplex wave migration improves efficiency of coalbed methane prediction. The work has been carried out based on 3D seismic survey conducted at one of the coalmines in the Donets Basin (Ukraine).

Imaging Slab Detachment Within the Western Hellenic Subduction Zone

AbstractThe Western Hellenic Subduction Zone (WHSZ) has been the focus of numerous seismic investigations, but its structure, particularly between ~150‐ and 250‐km depth, remains poorly understood. Many questions exist regarding the slab geometry at these intermediate depths, including whether the slab displays any tears related to tectonic processes along the WHSZ; however, local and regional studies only provide limited depth coverage, and the coarser resolution associated with broader‐scale investigations makes it difficult to discern detailed slab structure. Here, we have employed an adaptively parameterized inversion scheme to develop a new P wave tomography model for the WHSZ that bridges the gap between regional‐ and broader‐scale studies. Our new model highlights a trench‐parallel tear in the subducting lithosphere between northern Greece and the Gulf of Corinth. Further south, the imaged velocity structure indicates that the slab is retreating to the west and that it is thinned by the southward propagating tear, but the slab has not yet detached in this area. The tear well correlates with the down‐dip limit of seismicity in central Greece, while the steeply dipping slab between ~60‐ and 200‐km depth beneath southern Greece coincides with a steeper and deeper Wadati‐Benioff zone. While the slab continues into the lower mantle, earthquakes terminate at ~200‐km depth, and this is best attributed to dehydration processes in the subducting lithosphere. The southern extent of the tear imaged in our study also coincides with volcanic centers in eastern Peloponnese. Our results suggest that the trench‐parallel tear strongly influences seismicity and volcanism throughout Greece.

Seismic Collapse Performance of Jacket Offshore Platforms with Time-Variant Zonal Corrosion Model

ABSTRACT Corrosion of offshore platforms is inevitable. In an ocean corrosion environment, the strength of a platform is weakened greatly. When simultaneously subjected to earthquakes or other extreme loads, the ultimate bearing capacity of the corroded platform is dramatically reduced, resulting in compounded damage from both corrosion and earthquake. Thus, the influence of corrosion cannot be neglected in the seismic performance investigation of platforms. The commonly used corrosion model in platform design is uniform corrosion, and the corrosion rate rule for any parts or zones in a platform is the same. In real cases, however, there are significant differences between the corrosion characteristics in different parts of a platform. Based on theoretical aspects and measured data, a zonal time-variant corrosion model of a platform is developed for a seismic collapse performance investigation. The pushover and incremental dynamic analysis (IDA) methods are adopted here to calculate the collapse margin ratio (CMR), there serve strength ratio (RSR) and ductility coefficient (μ) that are frequently used for the safety reserve evaluation of a platform. The failure reason and collapse probability of platforms considering different service periods are compared. The most prominent feature of the proposed time-variant zonal corrosion model is to capture potential switch of weak location and resulting failure path of corroded jacket offshore platforms although the proposed model needs further calibration by more reliable in-field measured data. As expected, corrosion can definitely cause a reduction in earthquake resistance of a jacket offshore platform, as well as ultimate deformability. The coupled effect between the time-variant vibration properties of the platform and the spectral characteristics of selected motions, the collapse-level spectral acceleration (SA) does not always decrease with increasing corrosion degree. The curves corresponding to normalized CMR and RSR agree very well with each other in the early corrosion development stage and service period beyond 30 years. Some distinct differences can be found during the two stages, with the greatest difference up to 10% for the example platform.

An Investigation of Seismicity Induced by Hydraulic Fracturing in the Sichuan Basin of China Based on Data from a Temporary Seismic Network

An Investigation of Seismicity Induced by Hydraulic Fracturing in the Sichuan Basin of China Based on Data from a Temporary Seismic Network

Giant Success for NASA when the InSight Probe has Reached "Safety" on Mars

InSight-Studying the 'Inner Space' of Mars. InSight, short for Interior Exploration using Seismic Investigations, Geodesy and Heat Transport, is a Mars lander designed to give the Red Planet its first thorough checkup since it formed 4.5 billion years ago. It is the first outer space robotic explorer to study in-depth the "inner space" of Mars: Its crust, mantle and core. Studying Mars' interior structure answers key questions about the early formation of rocky planets in our inner solar system - Mercury, Venus, Earth and Mars - more than 4 billion years ago, as well as rocky exoplanets. InSight also measures tectonic activity and meteorite impacts on Mars today. The lander uses cutting edge instruments, to delve deep beneath the surface and seek the fingerprints of the processes that formed the terrestrial planets. It does so by measuring the planet's "vital signs": Its "pulse" (seismology), "temperature" (heat flow) and "reflexes" (precision tracking). This mission is part of NASA's Discovery Program for highly focused science missions that ask critical questions in solar system science.

Detection of seismic events on Mars: a lunar perspective

The interior structures of planets are attracting more and more detailed attention; these studies could be of great value in improving our understanding of the early evolution of Earth. Seismological investigations of planet interiors rely primarily on seismic waves excited by seismic events. Since tectonic activities are much weaker on other planets, e.g. Mars, the magnitudes of their seismic events are much smaller than those on Earth. It is therefore a challenge to detect seismic events on planets using such conventional techniques as short-time average/long-time average (STA/LTA) triggers. In pursuit of an effective and robust scheme to detect small-magnitude events on Mars in the near future, we have taken Apollo lunar seismic observations as an example of weak-activity data and developed an event-detection scheme. The scheme reported here is actually a two-step processing approach: the first step involves a despike filter to remove large-amplitude impulses arising from large temperature variations; the second step employs a matched filter to unmask the seismic signals from a weak event hidden in the ambient and scattering noise. The proposed scheme has been used successfully to detect a moonquake that was not in the known moonquake catalogue, demonstrating that the two-step strategy is a feasible method for detecting seismic events on planets. Our scheme will provide a powerful tool for seismic data analysis of the Interior Exploration using Seismic Investigations, Geodesy and Heat Transport (InSight) mission, and China’s future lunar missions.

ТЕХНОГЕННЫЙ СЛОЙ В МЕСТАХ ПРОВЕДЕНИЯ ПОДЗЕМНЫХ ЯДЕРНЫХ ВЗРЫВОВ НА ПРИМЕРЕ СЕМИПАЛАТИНСКОГО ПОЛИГОНА

Results of seismic investigation of the underground nuclear explosions area at the Semipalatinsk test site are considered. Using refracted waves method subsurface zones of surrounding geological media disintegration were revealed. These zones are characterized by decrease of P and S waves velocity on the value of 0,5-1,5 km/s and increase of Poisson coefficient on 0,07. Estimation of the induced fracturing was done; parameter of crack density measures up to 0,45.

Seismic investigation of pushover methods for concrete piers of curved bridges in plan

Seismic investigation of pushover methods for concrete piers of curved bridges in plan

Repeatability of high-resolution 3D seismic data

High-resolution 4D (HR4D) seismic data have the potential for improving the current state-of-the-art in detecting shallow ([Formula: see text] below seafloor) subsurface changes on a very fine scale (approximately 3–6 m). Time-lapse seismic investigations commonly use conventional broadband seismic data, considered low to moderate resolution in our context. We have developed the first comprehensive time -lapse analysis of high-resolution seismic data by assessing the repeatability of P-cable 3D seismic data (approximately 30–350 Hz) with short offsets and a high density of receivers. P-cable 3D seismic data sets have for decades been used to investigate shallow fluid flow and gas-hydrate systems. We analyze P-cable high-resolution 4D (HR4D) seismic data from three different geologic settings in the Arctic Circle. The first two are test sites with no evidence of shallow subsurface fluid flow, and the third is an active seepage site. Using these sites, we evaluate the reliability of the P-cable 3D seismic technology as a time-lapse tool and establish a 4D acquisition and processing workflow. Weather, waves, tide, and acquisition-parameters such as residual shot noise are factors affecting seismic repeatability. We achieve reasonable quantitative repeatability measures in stratified marine sediments at two test locations. However, repeatability is limited in areas that have poor penetration of seismic energy through the seafloor, such as glacial moraines or rough surface topography. The 4D anomalies in the active seepage site are spatially restricted to areas of focused fluid flow and might likely indicate changes in fluid flow. This approach can thus be applied to detect migration of fluids in active leakage structures, such as gas chimneys.

Dynamic behavior of double and triple adjacent 2D hills using boundary element method

A 2D boundary element method with material damping is developed in order to seismic investigation of constructions with different configurations. The boundary element algorithm, which utilized the time-convoluted kernels is employed in order to incorporate proportional damping. In order to investigate the seismic reaction of two dimensional double and triple semi-sine formed hills subjected to vertical P and SV waves by using a developed viscoelastic boundary element algorithm and responses are presented in the form of graphs, amplification pictures and displacement. In addition, the influences of various damping proportions on site of semi-sine hills with various shapes are analyzed. It can be concluded from the results that the crest of homogeneous adjacent hills have similar shape ratio, potential and larger maximum amplification in comparison with the crest of single hills. Although this difference is increased by increasing shape ratio, it is negligible within the proportions of study shape. In addition, multiplicity of hills increased frequency characteristic of amplification curve and the number of peaks and valleys.

Pre-mission InSights on the Interior of Mars

Abstract The Interior exploration using Seismic Investigations, Geodesy, and Heat Trans- port (InSight) Mission will focus on Mars’ interior structure and evolution. The basic structure of crust, mantle, and core form soon after accretion. Understanding the early differentiation process on Mars and how it relates to bulk composition is key to improving our understanding of this process on rocky bodies in our solar system, as well as in other solar systems. Current knowledge of differentiation derives largely from the layers observed via seismology on the Moon. However, the Moon’s much smaller diameter make it a poor analog with respect to interior pressure and phase changes. In this paper we review the current knowledge of the thickness of the crust, the diameter and state of the core, seismic attenuation, heat flow, and interior composition. InSight will conduct the first seismic and heat flow measurements of Mars, as well as more precise geodesy. These data reduce uncertainty in crustal thickness, core size and state, heat flow, seismic activity and meteorite impact rates by a factor of 3–10× relative to previous estimates. Based on modeling of seismic wave propagation, we can further constrain interior temperature, composition, and the location of phase changes. By combining heat flow and a well constrained value of crustal thickness, we can estimate the distribution of heat producing elements between the crust and mantle. All of these quantities are key inputs to models of interior convection and thermal evolution that predict the processes that control subsurface temperature, rates of volcanism, plume distribution and stability, and convective state. Collectively these factors offer strong controls on the overall evolution of the geology and habitability of Mars.

Optical-Performance Testing of the Laser RetroReflector for InSight

In the framework of the scientific activities foreseen by the NASA, ASI and INFN agreement for the InSight Mars lander mission (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport), we characterized the optical performance of the LaRRI instrument (Laser RetroReflector for InSight), through two sets of in-air solar-thermo-optical tests carried out at the SCF_Lab (Satellite/lunar/GNSS laser ranging/altimetry and cube/microsat Characterization Facilities Laboratory) of INFN–LNF in Frascati, Italy. The in-air tests consisted of optical and thermal measurements carried out by: (1) varying LaRRI’s bulk temperature (without solar illumination); (2) illuminating LaRRI with a solar spectrum; in both cases, LaRRI was interrogated with a laser at varying incidence angles w.r.t. its surface. This paper describes the tests and their results, which provide a first characterization of LaRRI’s optical and thermal behaviour in approximate Mars surface conditions.

The Thermal State and Interior Structure of Mars

AbstractThe present‐day thermal state, interior structure, composition, and rheology of Mars can be constrained by comparing the results of thermal history calculations with geophysical, petrological, and geological observations. Using the largest‐to‐date set of 3‐D thermal evolution models, we find that a limited set of models can satisfy all available constraints simultaneously. These models require a core radius strictly larger than 1,800 km, a crust with an average thickness between 48.8 and 87.1 km containing more than half of the planet's bulk abundance of heat producing elements, and a dry mantle rheology. A strong pressure dependence of the viscosity leads to the formation of prominent mantle plumes producing melt underneath Tharsis up to the present time. Heat flow and core size estimates derived from the InSight (Interior Exploration using Seismic Investigations, Geodesy and Heat Transport) mission will increase the set of constraining data and help to confine the range of admissible models.

Seismic investigation of icy crust covering subsurface oceans of Europa and Ganymede: Preliminary assessment of hypothetical experiment using impactor

Jupiter's satellite Europa is believed to harbor a global ocean beneath its ice-covered surface. But the thickness of this ice, despite its significance to the habitability of this moon, is unknown: estimates range from as thin as hundreds of meters to as thick as tens of kilometers. In this paper, we investigate the feasibility of a hypothetical experiment in which the ice's thickness is measured via seismic analysis. The assumed scenario calls for a seismometer to be placed on the satellite's surface to detect the ice surface's seismic response induced by an artificial impact event. Our hypothetical experiment could be applied at Europa as well as at Ganymede. For both satellites, two impact scenarios are considered: a low-energy-impact case, in which an orbiter probe impacts the ice at the end of the mission, and a high-energy-impact case, in which a spent upper rocket stage impacts the ice upon Jupiter arrival. We find that an impactor-induced seismic investigation is a promising add-on experiment in future missions to the icy moons of Jupiter.

High-Resolution Seismic Reflection Investigation of Subsidence and Sinkholes at an Abandoned Coal Mine Site in South Africa

The high-resolution seismic reflection method was conducted at an abandoned coal mine site located in the Benoni area, near the city of Johannesburg, South Africa, with the aim of investigating the subsidence- and sinkhole-related features that are commonly observed in the area. Like many old abandoned coal mine sites, the study area lacks adequate mine records that show the extent of the underground coal mining activities that took place in the area in the late 1930s. The preliminary geotechnical investigation conducted in the study area using percussion drilling had also confirmed the existence of underlying weathered dolomitic rocks that may give rise to dolomite-related sinkholes and subsidence. The seismic survey has revealed the occurrence of subsidence and sinkhole features in the area to be due to the collapse of the colliery roof into subsurface voids caused by coal extraction that took place at the depth between 7 and 13 m, as well as the dissolution cavities that exist within the underlying dolomite formation at the depth of about 50 m below the surface. The size of the coal-mining-related voids varies between 10 and 15 m and corresponds to the size of the room and pillar mining technique employed in the coal extraction, while the size of the dissolution cavities that exist within the underlying dolomite formation varies from 2 to 10 m.