Spatial Distribution Of Damage Research Articles

Low field MRI study of the potato cell membrane electroporation by pulsed electric field

The effects of high voltage pulsed electric fields (PEF) applied to potato tubers were examined by the contrast enhanced, low field Magnetic Resonance Imaging (MRI). This is a non-destructive, and relatively inexpensive method that allows to monitor the spatial distribution of damages caused by the pulses and their evolution in time. The MRI results confirmed the irreversible damage of the potato tuber cell membranes caused by the PEF treatment, leading to non-selective flow of ions. The extent of electroporation was also evaluated by electrical conductivity measurements, as well as by compression tests and compared with the MRI. On the basis of these results, the PEF method can be optimized in applications aiming at the increase of the permeability of potato cell membranes.

Noninvasive Whole-Body Imaging of Phosphatidylethanolamine as a Cell Death Marker Using 99mTc-Duramycin During TNF-Induced SIRS.

Systemic inflammatory response syndrome (SIRS) is an inflammatory state affecting the whole body. It is associated with the presence of pro- and antiinflammatory cytokines in serum, including tumor necrosis factor (TNF). TNF has multiple effects and leads to cytokine production, leukocyte infiltration, and blood pressure reduction and coagulation, thereby contributing to tissue damage and organ failure. A sterile mouse model of sepsis, TNF-induced SIRS, was used to visualize the temporal and spatial distribution of damage in susceptible tissues during SIRS. For this, a radiopharmaceutical agent, 99mTc-duramycin, that binds to exposed phosphatidylethanolamine on dying cells was longitudinally visualized using SPECT/CT imaging. Methods: C57BL/6J mice were challenged with intravenous injections of murine TNF or vehicle, and necrostatin-1 was used to interfere with cell death. Two hours after vehicle or TNF treatment, mice received 99mTc-duramycin intravenously (35.44 ± 3.80 MBq). Static whole-body 99mTc-duramycin SPECT/CT imaging was performed 2, 4, and 6 h after tracer injection. Tracer uptake in different organs was quantified by volume-of-interest analysis using PMOD software and expressed as SUVmean After the last scan, ex vivo biodistribution was performed to validate the SPECT imaging data. Lastly, terminal deoxynucleotidyl-transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining was performed to correlate the obtained results to cell death. Results: An increased 99mTc-duramycin uptake was detected in mice injected with TNF, when compared with control mice, in lungs (0.55 ± 0.1 vs. 0.34 ± 0.05), intestine (0.75 ± 0.13 vs. 0.56 ± 0.1), and liver (1.03 ± 0.14 vs. 0.64 ± 0.04) 4 h after TNF and remained significantly elevated until 8 h after TNF. The imaging results were consistent with ex vivo γ-counting results. Significantly increased levels of tissue damage were detected via TUNEL staining in the lungs and intestine of mice injected with TNF. Interestingly, necrostatin-1 pretreatment conferred protection against lethal SIRS and reduced the 99mTc-duramycin uptake in the lungs 8 h after TNF (SUV, 0.32 ± 0.1 vs. 0.51 ± 0.15). Conclusion: This study demonstrated that noninvasive 99mTc-duramycin SPECT imaging can be used to characterize temporal and spatial kinetics of injury and cell death in susceptible tissues during TNF-induced SIRS, making it useful for global, whole-body assessment of tissue damage during diseases associated with inflammation and injury.

FLOOD HISTORY ANALYSIS AND ITS CONTRIBUTION TO FLOOD HAZARD ASSESSMENT. THE CASE OF MARATHONAS, GREECE

Flood history analysis contributes decisively to a more realistic assessment of flood hazard. In this work, systematic data collection on past flood events in Marathonas area (Attica, Greece) together with the development of a database, allowed the thorough study of flooding phenomena and their evolution over time. The study area consists of three dominant catchments with rich flooding history, namely Rapentosa, Charadros and Kato Souli. Information gathered from governmental and insurance organizations, emergency agencies, the press, field interviews and other documentary sources, along with geomorphologic and geologic evidence, were stored, structured and analyzed in a GIS platform and were used to reconstruct flood events with detail. Valuable results were produced concerning the causes, the characteristics, the spatial distribution of damages and the extent of inundation for each event. Moreover, the rate of recurrence of flooding phenomena was calculated across the floodplain, so that the areas of higher risk were identified and delineated. The active part of the floodplain was outlined and its migration overtime was studied. Furthermore, the methodology underlined the imperfections of the existing risk mitigation strategy and the past emergency experiences were appraised in a way that they highlight the priorities and will help improve management of future situations of risk.

A multi-frequency fatigue testing method for wind turbine rotor blades

Rotor blades are among the most delicate components of modern wind turbines. Reliability is a crucial aspect, since blades shall ideally remain free of failure under ultra-high cycle loading conditions throughout their designated lifetime of 20–25 years. Full-scale blade tests are the most accurate means to experimentally simulate damage evolution under operating conditions, and are therefore used to demonstrate that a blade type fulfils the reliability requirements to an acceptable degree of confidence. The state-of-the-art testing method for rotor blades in industry is based on resonance excitation where typically a rotating mass excites the blade close to its first natural frequency. During operation the blade response due to external forcing is governed by a weighted combination of its eigenmodes. Current test methodologies which only utilise the lowest eigenfrequency induce a fictitious damage where additional tuning masses are required to recover the desired damage distribution. Even with the commonly adopted amplitude upscaling technique fatigue tests remain a time-consuming and costly endeavour. The application of tuning masses increases the complexity of the problem by lowering the natural frequency of the blade and therefore increasing the testing time. The novel method presented in this paper aims at shortening the duration of the state-of-the-art fatigue testing method by simultaneously exciting the blade with a combination of two or more eigenfrequencies. Taking advantage of the different shapes of the excited eigenmodes, the actual spatial damage distribution can be more realistically simulated in the tests by tuning the excitation force amplitudes rather than adding tuning masses. This implies that in portions of the blade the lowest mode is governing the damage whereas in others higher modes contribute more significantly due to their higher cycle count. A numerical feasibility study based on a publicly available large utility rotor blade is used to demonstrate the ability of the proposed approach to outperform the state-of-the-art testing method without compromising fatigue test requirements. It will be shown that the novel method shortens the testing time and renders the damage evolution with a higher degree of fidelity.

Temporal changes of the frequency of spring frost damages in the main fruit growing regions in Western Hungary and in East Hungary

Most of the risk in Hungarian fruit growing is the damage caused by late spring frosts. The frequency of late frosts seems to increase nowadays. The aim of the study was to check this contention: what is the real probability of the damages. Based on earlier experiences, the physiological LT50 function has been elaborated for new fruit varieties, which are eligible to moderate the danger when being threatened by frost. By means of this technique, the probability of freezing is distinguished between frost susceptible, frost resistant and medium frost resistant fruit species and varieties around their blooming time. The degree of frost damage depends on the duration and severity of the low temperature and not at least on the frost tolerance of the plant. For that purpose, the frequencies of frost damages were studied at two Transdanubian and two Trans-Tisza fruit growing sites by means of a meteorological database for the 60-year-long period 1951–2010. Being aware of the LT50 values changing during the phonological phases of the fruit trees from budding, bloom, fruit set and fruit growth, the number and date of critical (frosty) days could be settled. An important role is attributed to the orographic relief and the height above the sea level of the site, as 20–30 m differences and expositions may become decisive within the same plantation. The spatial distribution of damages is also dependent on the air circulations within the Carpathian basin. At the southern and northern borders of the country, especially valley bottoms represent additional risks of frost. Most spring frost damages are experienced in April 20–22, and cause heavy damages by temperature minima between – 3°C and – 6°C. The severity of damage depends largely on the temperature of the preceding few days. The earlier bloom the heavier damage is expected. The study is emphasising the importance of the varieties. Frost tolerance of some varieties may lower the risk of spring frosts by 40–50%, as experienced on the plantations. The quantifi cation of the risks based on data raised during the last years will be suitable to defi ne the security of yields of each growing site successfully.

The combined use of PSInSAR and UAV photogrammetry techniques for the analysis of the kinematics of a coastal landslide affecting an urban area (SE Spain)

In the present work, the case of the Carmenes del Mar resort (Granada, Spain) is shown. It can be considered one of the most extreme examples on the Mediterranean coast of severe pathologies associated with urban development on coastal landslides. The resort, with 416 dwellings, was partially built on a deep-seated landslide which affects a soft formation composed of dark graphite schists. In November 2015, the City Council officially declared a state of emergency in the resort and 24 dwellings have already been evacuated. We have used two remote sensing techniques to monitor the landslide with the aim of identifying and measuring a wide range of displacements rates (from mm/year to m/year): (1) PSInSAR, exploiting 25 ENVISAT SAR images acquired from May 2003 to December 2009, and (2) photogrammetry, considering the output from two Unmanned Aerial Vehicle (UAV) flights made in June 2015 and January 2016 and the outdated photos from a conventional flight in 2008. The relationship between the geology of the site, data from PS deformation measurements, building displacements, rainfall and damage observed and their temporal occurrence allows a better understanding of the landslide kinematics and both the spatial and temporal evolution of the instability. Results indicate building displacements of up to 1.92 m in 8 years, a clear lithological control in the spatial distribution of damage and a close relationship between the most damaging events and water recharge episodes (rainy events and leaks from swimming pools and the water supply network). This work emphasises the need to incorporate geohazards into urban planning, including policies to predict, prepare for and prevent this type of phenomenon.

Development of evacuation models for moderate seismic zones: A case study of Montreal

The objectives of this work is develop an innovative multidisciplinary methodology to estimate shelter needs and evacuation scenarios in the event of a major earthquake in a region of moderate seismic activity that never experienced such an event in modern history. Shelter demand is estimated through a binary discrete choice model based on a carefully designed survey using methodologies developed by seismologists, structural engineers, urban planners and transportation engineers. For each scenario, shelter allocation is based on the spatial distribution of damage and population. The methodology is demonstrated for the city of Montreal which is located in a moderately active seismic region. The results of the choice model are compared to those obtained with the HAZUS methodology which underestimates shelter needs. The study finds that the factors influencing evacuation decisions in HAZUS are also important for Montreal; however, other additional variables such as road condition, distance between home and shelter, power outage, and number of children are also significant. The traffic model is applied after the earthquake for the most vulnerable areas in Montreal. The OREMS software is used to simulate traffic behavior during emergency evacuations and identifies evacuation links with potential traffic congestion. The traffic performance of highways is better than arterial roads in the highly vulnerable areas. Most of the main roads and access roads in the Plateau Mont-Royal and Cote-de-Neiges boroughs are highly congested in the aftermath of earthquake.

The 1719 El Salvador Earthquake: An M>7.0 Event in the Central American Volcanic Arc?

In the regions where few field neotectonics and paleoseismic studies have been performed (e.g., Central America), the interpretation of the seismic sources responsible for the historical (preinstrumental) catastrophic earthquakes lies almost entirely in the spatial distribution of damage interpreted from historical sources, mainly fragmentary written documents. The occurrence of catastrophic earthquakes affecting this region justifies the necessity of a deeper analysis of the geologic implications of the more significant historical earthquakes in light of the new insights. Recent advances in the identification and dating of surface‐rupture evidences along the central El Salvador volcanic arc led us to revisit some historical evidence of damage along this region and to combine geologic (paleoseismic) evidence with damage distribution. At least 11 destructive earthquakes have occurred in El Salvador since 1900 (White and Harlow, 1993; Fig. 1). These events caused more than 3000 deaths as a consequence of strong ground motions and/or subsequent landslides (Bommer et al. , 2002). The instrumental earthquake record shows that large ( M w>7) events occurred as reverse fault events along the interface between the subducted plate and the over‐riding continental plate or as normal‐faulting events within the subduction plate resulting from extensional forces generated by slab‐pull forces or by bending of the subduction plate (Alvarez‐Gomez, 2009). Onshore, instrumental earthquakes have been reported with moderate magnitudes ( M w 7.0 usually have been assigned to the subduction zone, whereas historical records with M w 7.0) associated with the rupture of the El Salvador fault zone …

Nonparametric estimation of wave dispersion in high‐rise buildings by seismic interferometry

SUMMARYInterferometric identification and health monitoring of high‐rise buildings has been gaining increasing interest in recent years. The wave dispersion in the structure has been largely ignored in these efforts but needs to be considered to further develop these methods. In this paper, (i) the goodness of estimation of vertical wave velocity in buildings, as function of frequency, by two nonparametric interferometric techniques is examined, using realistic fixed‐base Timoshenko beam benchmark models. Such models are convenient because the variation of phase and group velocities with frequency can be derived theoretically. The models are those of the NS and EW responses of Millikan Library. One of the techniques, deconvolution interferometry, estimates the phase velocity on a frequency band from phase difference between motions at two locations in the structure, while the other one estimates it approximately at the resonant frequencies based on standing wave patterns. The paper also (ii) examines the modeling error in wave velocity profiles identified by fitting layered shear beam in broader band impulse response functions of buildings with significant bending flexibility. This error may affect inferences on the spatial distribution of damage from detected changes in such velocity profiles. Copyright © 2014 John Wiley & Sons, Ltd.

European cold wave during February 2012 and impacts in wine growing regions of Moldavia (Romania)

A severe cold wave hits a large part of Europe between late January and mid-February 2012 and caused damages in the vineyard of Moldavia in Northeastern Romania. During the cold wave, the daily minimum temperature fell near −30 °C at some weather stations in Moldavia, but the hilly terrain caused strong temperature differences at small scales: up to 10 °C in a few kilometres. Three main cold spells with very low minimum temperatures were identified in association with the succession of three circulation types (according to the Hess-Brezowsky classification): Fennoscandian high anticyclonic (HFA, January 29–February 4), Central European ridge (BM, February 5–7) and northeast anticyclonic NEA (NEA, February 8–11). A multi-scale agroclimatic analysis in the vineyard of Cotnari (Moldavia, Romania) was carried out in the particular meteorological context of the early 2012 European cold wave. The results especially pointed out the local-scale (topoclimatic) effects on the high spatial variability of temperature and consequently a contrasting spatial distribution of damage on grape vine. The analysis of data recorded from temperature loggers installed in several test sites in the vineyard of Cotnari, depending on its topographical features, and of the observations of frost damage on grape vines (on vine buds, vine canes and even vine arms and trunks) pointed out a significant correlation between the topographic position and the grape vine variety.

The 23 October 2011MW7.0 Van (Eastern Turkey) Earthquake: Interpretations of Recorded Strong Ground Motions and Post-Earthquake Conditions of Nearby Structures

A major thrust-fault earthquake of MW= 7.0 occurred on 23 October 2011 at 10:41:21 UTC in the eastern Anatolian region of Turkey, severely affecting the nearby towns of Van and Erciş. In this study, a few strong-motion records from the epicentral area are analyzed in order to investigate the characteristics of the ground motions. Also reported are the post-earthquake field observations for various types of structures, such as buildings, bridges, historical structures, tunnels, and dams within the vicinity of the fault plane. The spatial distribution of damage indicates a noticeable hanging-wall effect. The special-type structures are observed to experience far less damage, as opposed to the building structures in the region pointing to the need for strict compliance to seismic building code and the corresponding construction requirements.

Multi-Physics Modeling of Fire-Induced Damage in High-Performance Concrete

The response of high-performance concrete (HPC) to rapid heating due to exposure to fire with air temperatures exceeding 700°C is analyzed. The analysis focuses on coupled thermal-mechanical-transport processes at the mesoscale in the first 10 minutes of exposure during which heating rates on the order of 10 °C/minute and temperature gradients on the order of 15 °C/cm are involved. The driving forces for damage considered are thermomechanical stresses and internal pore pressure resulting from the expansion of water within the material. The HPC is modeled as a two-phase composite consisting of a cementitious matrix and a population of quartz aggregate particles. Mesostructures with aggregate sizes of 400-1600 μm and aggregate volume fractions of 10-30% are considered. To capture the development of stresses and pore pressure, the cementitious matrix is modeled using a coupled thermal-mechanical-transport formulation and the aggregate is modeled using a thermal-mechanical formulation. Simulations show that the composition of the mesostructures significantly influences the time and spatial distribution of damage. Materials with smaller aggregate sizes and the lower effective permeability are found to exhibit more rapid property degradation. The time to failure and depth of thermal spall are quantified as functions of structural variables. This framework and the mesostructure-response relations obtained serves as a tool for the design of HPC that are more resistant to fire-induced damage.

Fault Process and Broadband Ground-Motion Simulations of the 23 October 2011 Van (Eastern Turkey) Earthquake

Abstract On 23 October 2011 an M w 7.1 earthquake occurred in eastern Turkey, close to the towns of Van and Ercis, causing more than 600 casualties and widespread structural damage. The earthquake ruptured a 60–70 km long northeast–southwest fault with a thrust mechanism, in agreement with regional tectonic stress regime. We studied the fault process of the event and the recorded ground motions using different sets of data. Regional records (0.005–0.010 Hz) are used to constrain the centroid moment tensor solution. Near‐regional data, 100–200 km from the fault, are used for relocation of the hypocenter and, in the frequency range 0.05–0.15 Hz, for inversion of the rupture propagation by two methods: multiple point‐source model (ISOLA) and multiple finite‐extent (MuFEx) source model. MuFEx also provides an estimate of the model uncertainty, which is quite large due to unfavorable station distribution. We arrive at several plausible scenarios (equally well fitting the observed data including Global Positioning System coseismic displacements) with different styles of the rupture propagation. A few alternative source models are used for broadband (0.1–10 Hz) ground‐motion simulations by means of the hybrid integral‐composite source model. Only models comprising source complexities, such as a delayed rupture of shallow asperities, enable explanation of the acceleration record at the only available near‐fault station, which exhibits a long duration and two prominent wave groups. These complex rupture models are used to simulate the ground motion in the near‐fault area, specifically, at Van and Ercis, where records of the mainshock were missing, providing reasonable agreement with the observed spatial distribution of damage.

Experimental characterization of strain localization in rock

Abstract In this study, damage evolution and strain localization in sandstone have been experimentally investigated in uniaxial compression tests. A digital image correlation technique has been applied to obtain apparent strain fields which can visually display the deformation and damage evolution of rock. The experimental results show that regions with apparent strain concentration (RASC) develop at the initial loading stage and distribute diffusely on the sample surface which may correspond to the damaged areas. With incremental load, the RASCs localize spatially, probably via coalescence into a line-shaped area that behaves like a macroscopic crack leading to the eventual failure of the specimen. A factor DRASC representing the deviation of the average apparent strain in RASCs from the average on the whole sample surface and a localization factor Lf, are proposed to characterize the evolution of damage and localization. DRASC increases slowly in the initial phase of loading and rises rapidly after the onset of localization. Lf decreases during loading which indicate the localization of spatial distribution of damage. The two factors can be used to well reflect the damage evolution and strain localization of rock specimens under compression.

Whole-Body Imaging of High-Dose Ionizing Irradiation-Induced Tissue Injuries Using 99mTc-Duramycin

High-dose ionizing irradiation can cause extensive injuries in susceptible tissues. A noninvasive imaging technique that detects a surrogate marker of apoptosis may help characterize the dynamics of radiation-induced tissue damage. The goal of this study was to prove the concept of imaging the temporal and spatial distribution of damage in susceptible tissues after high-dose radiation exposure, using (99m)Tc-duramycin as a phosphatidylethanolamine-binding radiopharmaceutical. Rats were subjected to 15 Gy of total-body irradiation with x-rays. Planar whole-body (99m)Tc-duramycin scanning (n = 4 per time point) was conducted at 24, 48, and 72 h using a clinical γ-camera. On the basis of findings from planar imaging, preclinical SPECT data were acquired on control rats and on irradiated rats at 6 and 24 h after irradiation (n = 4 per time point). Imaging data were validated by γ-counting and histology, using harvested tissues in parallel groups of animals (n = 4). Prominent focal uptake was detected in the thymus as early as 6 h after irradiation, followed by a gradual decline in (99m)Tc-duramycin binding accompanied by extensive thymic atrophy. Early (6-24 h) radioactivity uptake in the gastrointestinal region was detected. Significant signal was seen in major bones in a slightly delayed fashion, at 24 h, which persisted for at least 2 d. This finding was paralleled by an elevation in signal intensity in the kidneys, spleen, and liver. The imaging results were consistent with ex vivo γ-counting results and histology. Relatively high levels of apoptosis were detected from histology in the thymus, guts, and bones, with the thymus undergoing substantial atrophy. As a proof of principle, this study demonstrated a noninvasive imaging technique that allows characterization of the temporal and spatial dynamics of injuries in susceptible tissues during the acute phase after high-dose ionizing irradiation. Such an imaging capability will potentially be useful for global, whole-body, assessment of tissue damage after radiation exposure. These data, in turn, will contribute to our general knowledge of tissue susceptibility to ionizing irradiation, as well as the onset and progression of tissue injuries.

Spatial localization of genes determined by intranuclear DNA fragmentation with the fusion proteins lamin KRED and histone KRED und visible light.

The highly organized DNA architecture inside of the nuclei of cells is accepted in the scientific world. In the human genome about 3 billion nucleotides are organized as chromatin in the cell nucleus. In general, they are involved in gene regulation and transcription by histone modification. Small chromosomes are localized in a central nuclear position whereas the large chromosomes are peripherally positioned. In our experiments we inserted fusion proteins consisting of a component of the nuclear lamina (lamin B1) and also histone H2A, both combined with the light inducible fluorescence protein KillerRed (KRED). After activation, KRED generates reactive oxygen species (ROS) producing toxic effects and may cause cell death. We analyzed the spatial damage distribution in the chromatin after illumination of the cells with visible light. The extent of DNA damage was strongly dependent on its localization inside of nuclei.The ROS activity allowed to gain information about the location of genes and their functions via sequencing and data base analysis of the double strand breaks of the isolated DNA. A connection between the damaged gene sequences and some diseases was found.

Robustness and uncertainties of seismic damage estimates at urban scale: a methodological comparison on the example of the city of Oran (Algeria)

The city of Oran is exposed to a significant seismic hazard, as almost all the northern Algeria territory, where numerous casualties and severe damage occurred in the last decades due to several moderate to large earthquakes. A mitigation policy should include the establishment of priorities to reduce the vulnerability of existing buildings based on the knowledge of the actual urban fabrics. The complexity of vulnerability assessment requires a gradual approach from the urban scale to the building scale. The study reported in this paper corresponds to the first step of such an approach, i.e., a preliminary study of the seismic vulnerability and expected damage within an urban district of the city of Oran, based on a non-dedicated data base from a building survey previously performed for other purposes. The main goals of this study are twofold: (1) an assessment of the degree of uncertainty and robustness of such results through a comparison of the results derived from different urban vulnerability methods (GNDT 2; RISK-UE LM1; and VULNERALP 2.0) and (2) an assessment of the actual level of seismic risk in the city of Oran. Cross-method comparisons and correlations highlight a satisfactory agreement between mean damage estimates at the urban scale, despite significant scattering at the single building scale, and uncertainty levels which vary significantly from one method to the other. For a given scenario, the three methods provide damage estimates lying within half an EMS damage degree of one another, with some systematic positive bias for VULNERALP and negative bias for RISK-UE LM1, especially for masonry buildings. The expected mean damage is very important for intensities 9 and 10, with an average damage grade around 3-4 for intensity 9 and 4-5 for intensity 10. The spatial distribution of damage systematically exhibits larger values in the northern, older, commercial area, than in the southern, more recent and more residential area, in relation to the building typology and the existence of several aggravating factors. Some areas of higher vulnerability / damage can be distinguished, which should receive particular attention for retrofitting priorities or urban planning decisions, also taking into account their cultural heritage value.

Method for evaluating flood disaster reduction measures in alluvial plains

AbstractWith attention focused on flood hazard risk from place to place on a whole flood plain before and after flood hazard reduction and mitigation countermeasures are implemented, the present study proposes a method for evaluating flood hazard risk described using a local inundation depth and its frequency of occurrence. The method is composed of a rainfall run‐off model, a 1‐D channel flow model, a depth‐integrated 2‐D flood model, and several sub‐models, such as of a potential damage curve and an evacuation rating curve. To test the applicability of the proposed method, a flood plain located in the northern lake area of Shiga prefecture is chosen for discussion. The spatial distribution of damage resulting from each flood is thus evaluated before and after countermeasures are implemented.

Micromechanics of inelastic compaction in two allochemical limestones

To investigate inelastic compaction in limestone we deformed in conventional triaxial configuration samples of two allochemical limestones: Indiana and Majella limestone with porosity of 14–16% and 30%, respectively. We described the microstructures associated with the damage evolution. Inelastic compaction in both limestones was associated with pore collapse that seemed to initiate from stress concentrations at the surface of a pore. Cataclasis appeared to develop preferentially around the macropores, in agreement with a recent study on a micritic limestone. Our new observations however showed that the spatial distribution of damage in the allochemical limestones can be complicated by its uneven partitioning among the allochems, micrite and sparite. In Indiana limestone, many allochems remain relatively intact even after the cement has undergone significant microcracking, with the implication that significant strength contrast exists between the allochems and cement. In Majella limestone, the asymmetry in damage intensity is not as pronounced, suggesting a less pronounced mechanical contrast between allochems and cement. In both limestones, significant mechanical twinning was observed in samples deformed to relatively high level of strain. We applied to our data a model, that treats a limestone as a dual porosity medium, with the total porosity partitioned between macroporosity and microporosity.

Spatial distribution of damage around faults in the Joe Lott Tuff Member of the Mount Belknap Volcanics, Utah: A mechanical analog for faulting in pyroclastic deposits on Mars

Volcanic ash is thought to comprise a large fraction of the Martian equatorial layered deposits and much new insight into the process of faulting and related fluid flow in these deposits can be gained through the study of analogous terrestrial tuffs. This study identifies a set of fault‐related processes that are pertinent to understanding the evolution of fault systems in fine‐grained, poorly indurated volcanic ash by investigating exposures of faults in the Miocene‐aged Joe Lott Tuff Member of the Mount Belknap Volcanics, Utah. The porosity and granularity of the host rock are found to control the style of localized strain that occurs prior to and contemporaneous with faulting. Deformation bands occur in tuff that was porous and granular at the time of deformation, while fractures formed where the tuff lost its porous and granular nature due to silicic alteration. Non‐localized deformation of the host rock is also prominent and occurs through compaction of void space, including crushing of pumice clasts. Significant off‐fault damage of the host rock, resembling fault pulverization, is recognized adjacent to one analog fault and may reflect the strain rate dependence of the resulting fault zone architecture. These findings provide important new guidelines for future structural analyses and numerical modeling of faulting and subsurface fluid flow through volcanic ash deposits on Mars.