Change of apparent segmentation of the San Andreas fault around Parkfield from space geodetic observations across multiple periods

Sequences of earthquakes are commonly represented as a succession of periods of interseismic stress accumulation followed by coseismic and postseismic phases of stress release. Because the recurrence time of large earthquakes is often greater than the available span of space geodetic data, it has been challenging to monitor the evolution of interseismic loading in its entire duration. Here we analyze large data sets of surface deformation at different key episodes around the Cholame, Parkfield and creeping segments of the San Andreas Fault that show evidence of significant deceleration of fault slip during the interseismic period. We compare the average fault slip rates before and after the 2004 Mw6 Parkfield earthquake, in the 1986–2004 and 2006–2012 periods, respectively, avoiding 2 years of postseismic deformation after 2004. Using a combination of GPS data from the Plate Boundary Observatory, the Southern California Earthquake Center Crustal Motion Map and the Bay Area Velocity Unification networks and interferometric synthetic aperture radar from the Advanced Land Observing Satellite (ALOS) and Envisat satellites, we show that the area of coupling at the transition between the Parkfield and Cholame segments appears larger later in the interseismic period than it does earlier on. While strong plate coupling is uniform across the Parkfield and Cholame segments in the 1986–2004 period, creep occurs south of the 2004 epicenter after 2006, making segmentation of the San Andreas Fault south of Parkfield more clearly apparent. These observations indicate that analyses of surface deformation late in the earthquake cycle may overestimate the area of plate coupling. A fault surface creeping much below plate rate may in some case be a region that does not promote earthquake nucleation but rather just be at a slower stage of its evolution. Our analysis also shows signs of large variation of slip velocity above and below plate rate in the creeping segment indicating that cycles of weakening and hardening can also be at play in dominantly aseismic areas

Surface displacement of the Mw 7 Machaze earthquake (Mozambique): Complementary use of multiband InSAR and radar amplitude image correlation with elastic modelling.

International audienceIn this paper we investigate the surface displacement related to the 2006 Machaze earthquake using Synthetic Aperture Radar Interferometry (InSAR) and sub-pixel correlation (SPC) of radar amplitude images. We focus on surface displacement measurement during three stages of the seismic cycle. First, we examined the co-seismic stage, using an Advanced SAR (ASAR) sensor onboard the Envisat satellite. Then we investigated the post-seismic stage using the Phase Array L-band SAR sensor (PALSAR) onboard the ALOS satellite. Lastly, we focussed on the inter-seismic stage, prior to the earthquake by analysing the L20 and JERS-1 SAR data. The high degree of signal decorrelation in the C-band co-seismic interferogram hinders a correct positioning of the surface rupture and correct phase unwrapping. The post-seismic L-band interferograms reveal a time-constant surface displacement, causing subsidence of the surface at a ~ 5 cm/yr rate. This phenomenon continued to affect the close rupture field for at least two years following the earthquake and intrinsically reveals a candidate seismogenic fault trace that we use as a proxy for an inversion against an elastic dislocation model. Prior to the earthquake, the JERS interferograms do not indicate any traces of pre-seismic slip on the sismogenic fault. Therefore, slip after the earthquake is post seismic, and it was triggered by the Machaze earthquake. This feature represents a prominent post-seismic slip event rarely observed in such a geodynamic context

Time-variable 3D ground displacements from High-Resolution Synthetic Aperture Radar (SAR). Application to La Valette landslide (South French Alps).

International audienceWe apply an image correlation technique to multi-orbit and multi-temporal High-Resolution (HR) SAR data. Image correlation technique has the advantage of providing displacement maps in two directions; e.g. the Line of Sight direction (LoS) and the Azimuth direction. This information, derived from the two modes of data acquisition (ascending and descending), can be combined routinely to infer the three dimensional surface displacement field at different epochs. In this study, a methodology is developed to characterize the displacement pattern of the large La Valette landslide (South French Alps) using TerraSAR-X images acquired in 2010. The results allow mapping the dynamics of different units of the La Valette landslide at high spatial resolution. The study demonstrates the potential of this new application of High Resolution SAR image correlation technique for landslide ground surface deformation monitoring

Three-dimensional surface displacement of the 2008 May 12 Sichuan earthquake (China) derived from Synthetic Aperture Radar: evidence for rupture on a blind thrust

International audienceThe Sichuan earthquake,Mw7.9, struck the Longmen Shan (LMS) range front,China, on 2008 May 12, affecting an area of moderate historical seismicity where little active shortening has been previously reported. Recent studies based on space geodesy have succeeded in retrieving the far field surface displacements caused by the earthquake, but the near field (±25 km from the faults) coseismic surface displacement is still poorly constrained. Thus, shallow fault geometry and shallow coseismic slip are still poorly resolved. Here, for the first time for this earthquake, we combine C and L-band Synthetic Aperture Radar offsets data from ascending and descending tracks to invert for the 3-D surface displacement in the near coseismic field of the Sichuan earthquake. Our data, coupled with a simple elastic dislocation model, provide new results strongly suggesting the presence of a blind thrust striking along the range front and being active at depth during the earthquake. The presence of a rupture on a blind thrust brings new evidence for an out-of-sequence thrusting event and new elements for interpreting the tectonic strain partitioning in the LMS, which has important implications both for seismic hazard assessment and long-term evolution of the mountain belt

An evaluation of morphological and functional multi-parametric MRI sequences in classifying non-muscle and muscle invasive bladder cancer

Objectives: Our goal is to determine the ability of multi-parametric magnetic resonance imaging (mpMRI) to differentiate muscle invasive bladder cancer (MIBC) from non-muscle invasive bladder cancer (NMIBC). Methods: Patients underwent mpMRI before tumour resection. Four MRI sets, i.e. T2-weighted (T2W) + perfusion-weighted imaging (PWI), T2W plus diffusion-weighted imaging (DWI), T2W + DWI + PWI, and T2W + DWI + PWI + dif-fusion tensor imaging (DTI) were interpreted qualitatively by two radiologists, blinded to histology results. PWI, DWI and DTI were also analysed quantitatively. Accuracy was determined using histopathology as the reference standard. Results: A total of 82 tumours were analysed. Ninety-six percent of T1-labeled tumours by the T2W + DWI + PWI image set were confirmed to be NMIBC at histopathology. Overall accuracy of the complete mpMRI protocol was 94% in differentiating NMIBC from MIBC. PWI, DWI and DTI quantitative parameters were shown to be significantly different in cancerous versus non-cancerous areas within the bladder wall in T2-labelled lesions. Conclusions: MpMRI with DWI and DTI appears a reliable staging tool for bladder cancer. If our data are validated, then mpMRI could precede cystoscopic resection to allow a faster recognition of MIBC and accelerated treatment pathways. Key Points: • A critical step in BCa staging is to differentiate NMIBC from MIBC. • Morphological and functional sequences are reliable techniques in differentiating NMIBC from MIBC. • Diffusion tensor imaging could be an additional tool in BCa staging

Spatiotemporal evolution of surface creep in the Parkfield region of the San Andreas Fault (1993-2004) from synthetic aperture radar.

International audienceThe Parkfield section of the San Andreas Fault (SAF) is defined as a transitional portion of the fault between slip-release behavior types in the creeping section of the SAF to the northwest and the apparently locked section to the southeast. The Parkfield section is characterized by complex frictional fault behavior because it represents a transition zone from aseismic creep to stick-slip regime. At least six historic earthquakes of Mw ~6 have occurred in this area in 1881, 1901, 1922, 1934, 1966, and 2004. It was observed in the 2004 Mw 6.0 Parkfield earthquake that ~70% of the total (coseismic and postseismic) moment release occurred aseismically. To understand the SAF behavior in this area, it is of particular interest to measure and analyze, not only the spatial evolution of the surface displacement in this area, but also its evolution over time. Using radar data acquired by the European Space Agency's European Remote Sensing (ERS1-2) satellites, we constructed descending interferograms and retrieved time series of surface displacements along the central SAF for the decade preceding the 2004 Parkfield earthquake. We focus on characterizing the space and time evolution of surface creep in the Parkfield and Cholame sections. The spatial pattern of the interseismic displacement rate indicates that tectonic strain was not uniformly distributed along the strike of the fault between 1993 and 2004. Our data indicate not only a decrease in the creep rate from the Parkfield section to south of Highway-46 from 1.4 ±0.3 cm/y to 0.6 ±0.3 cm/y, but also a small but significant creep-rate increase in the Cholame section to 0.2 ±0.1 cm/y. The evidence for episodic creep in the Cholame section of the SAF south-east of Parkfield is in contrast with previously published interpretations of GPS and trilateration data. The Cholame section of the SAF merits close monitoring because it was likely the nucleation site of the 1857 Fort Tejón earthquake and because it has shown recent evidence of deep slow slip as revealed by deep tremors

The interferometry technics applied on residual subsidence analysis measurement of closure coal mines, example from Nord-Pas-de Calais coal mine, France

International audienceThis paper describes the residual movements associated with deep coalmines (France). The Nord-Pas-de Calais basin has been monitored since 10 years by traditional method. The interferometry technics are applied on Nord-Pas-de-Calais coal basin. In this study, both differential SAR Interferometry (DINSAR) and Persistent Scaterrers Interferometry (PSI) are used to estimate the induced deformations during 12 years (1992 to 2004) after the end of exploitation. 88 images of ERS scenes, distributed on two adjacent tracks, are processed, using DIAPASON software for DInSAR and GAMMA-IPTA for PSI. The area undergoes high temporal decorrelation due to the high amount of vegetation. Deformations are well detected; they present low amplitude with a maximum rate of only 1 cm/year during 7 years after the end of the exploitation. They show a good agreement with the traditional methods of levelling. A robust methodology can be developed to use Interferometry for surveying surface above abandoned minesL'article décrit les mouvements résiduels induit par l'exploitation de mines de charbon profondes (France). La surface est suivie depuis plus que 10 ans par la méthode de nivellement classique. La méthode d'interférométrie a également été utilisée dans le basin du Nord et du Pas-de-Calais, les deux techniques (SAR et PSI) ont été utilisées pour estimer les mouvements résiduels durant 12 ans (1992-2004) après l'arrêt de l'exploitation. 88 images de ERS ont été analysées en utilisant le code DIAPASON pour la méthode DInSAR et le code GAMMA-IPTA pour la méthode PSI. La zone étudiée est caractérisée par une couverture végétale très dense, ce qui induit une forte décorrélation temporelle. Les mouvements ont été bien détectés, ils présentent une amplitude de 1 cm/an pendant les 7 ans après l'arrêt des travaux miniers. Les résultants de l'interférométrie ont montré une cohérence avec les mesures par la méthode de nivellement traditionnel. Une méthodologie robuste peut-être développée pour suivre les mouvements induits par les exploitations minières abandonnée

Adult cardiac stem cell aging: A reversible stochastic phenomenon?

Aging is by far the dominant risk factor for the development of cardiovascular diseases, whose prevalence dramatically increases with increasing age reaching epidemic proportions. In the elderly, pathologic cellular and molecular changes in cardiac tissue homeostasis and response to injury result in progressive deteriorations in the structure and function of the heart. Although the phenotypes of cardiac aging have been the subject of intense study, the recent discovery that cardiac homeostasis during mammalian lifespan is maintained and regulated by regenerative events associated with endogenous cardiac stem cell (CSC) activation has produced a crucial reconsideration of the biology of the adult and aged mammalian myocardium. The classical notion of the adult heart as a static organ, in terms of cell turnover and renewal, has now been replaced by a dynamic model in which cardiac cells continuously die and are then replaced by CSC progeny differentiation. However, CSCs are not immortal. They undergo cellular senescence characterized by increased ROS production and oxidative stress and loss of telomere/telomerase integrity in response to a variety of physiological and pathological demands with aging. Nevertheless, the old myocardium preserves an endogenous functionally competent CSC cohort which appears to be resistant to the senescent phenotype occurring with aging. The latter envisions the phenomenon of CSC ageing as a result of a stochastic and therefore reversible cell autonomous process. However, CSC aging could be a programmed cell cycle-dependent process, which affects all or most of the endogenous CSC population. The latter would infer that the loss of CSC regenerative capacity with aging is an inevitable phenomenon that cannot be rescued by stimulating their growth, which would only speed their progressive exhaustion. The resolution of these two biological views will be crucial to design and develop effective CSC-based interventions to counteract cardiac aging not only improving health span of the elderly but also extending lifespan by delaying cardiovascular disease-related deaths

vegetation mapping from high resolution satellite images in the heterogeneous arid environments of socotra island yemen

Socotra Island (Yemen), a global biodiversity hotspot, is characterized by high geo- morphological and biological diversity. In this study, we present a high-resolution vegetation map of the island based on combining vegetation analysis and classification with remote sensing. Two different image classification approaches were tested to assess the most accurate one in mapping the vegetation mosaic of Socotra. Spectral signatures of the vegetation classes were obtained through a Gaussian mixture distribution model, and a sequential maximum a posteriori (SMAP) classification was applied to account for the heterogeneity and the complex spatial pattern of the arid vegetation. This approach was compared to the traditional maximum like- lihood (ML) classification. Satellite data were represented by a RapidEye image with 5 m pixel resolution and five spectral bands. Classified vegetation releves were used to obtain the training and evaluation sets for the main plant communities. Postclassification sorting was performed to adjust the classification through various rule-based operations. Twenty- eight classes were mapped, and SMAP, with an accuracy of 87%, proved to be more effective than ML (accuracy: 66%). The resulting map will represent an important instrument for the elaboration of conservation strategies and the sustainable use of natural resources in the island. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original pub- lication, including its DOI. (DOI: 10.1117/1.JRS.7.073527

Is land subsidence increasing the exposure to sea level rise in Alexandria, Egypt?

Delta margins are subject to relatively high rates of land subsidence and have the potential to significantly exacerbate future changes in sea levels predicted by global warming models used in impact studies. Through a combined analysis of GPS and persistent scatterer interferometry data, we determine that most of the coastline of Alexandria has been subject to moderate land subsidence over the past decade (0.4 mm/yr on average and up to 2 mm/yr locally). This contrasts to previous studies that suggested subsidence in excess of 3 mm/yr. Based on our findings, we infer that on multi-century to millennia timescales, land subsidence in the area of Alexandria is dominated by tectonic setting and earthquakes or gravitational collapse episodes of a growth fault, whereas on shorter interseismic decadal to century timescales, subsidence rates are likely steady and moderate, in agreement with natural compaction and dewatering of the observed Holocene sediment layer. Key Points Use of a combined analysis of GPS and PSI data Alexandria coastal are has been subject to moderate land subsidence Important considerations for local planning and policy development ©2013. American Geophysical Union. All Rights Reserved.The work presented in this article was supported by the French Research National Agency (ANR) through the CEP-2009 program under the grant number ANR-09-CEP-001-01 (Project CECILE or “Coastal Environmental Changes: Impact of sea LEvel rise”). Universitat de les Illes Balears provided a visiting professor grant for G. Wöppelmann, whereas M. Marcos acknowledges a “Ramon y Cajal” contract funded by the Spanish Ministry of SciencePeer Reviewe