Seven years of postseismic deformation following the 2003 Mw = 6.8 Zemmouri earthquake (Algeria) from InSAR time series

International audience[1] We study the postseismic surface deformation of the Mw 6.8, 2003 Zemmouri earthquake (northern Algeria) using the Multi-Temporal Small Baseline InSAR technique. InSAR time series obtained from 31 Envisat ASAR images from 2003 to 2010 reveal sub-cm coastline ground movements between Cap Matifou and Dellys. Two regions display subsidence at a maximum rate of 2 mm/yr in Cap Djenet and 3.5 mm/yr in Boumerdes. These regions correlate well with areas of maximum coseismic uplifts, and their association with two rupture segments. Inverse modeling suggest that subsidence in the areas of high coseismic uplift can be explained by afterslip on shallow sections (<5 km) of the fault above the areas of coseismic slip, in agreement with previous GPS observations. The earthquake impact on soft sediments and the ground water table southwest of the earthquake area, characterizes ground deformation of non-tectonic origin. The cumulative postseismic moment due to 7 years afterslip is equivalent to an Mw 6.3 earthquake. Therefore, the postseismic deformation and stress buildup has significant implications on the earthquake cycle models and recurrence intervals of large earthquakes in the Algiers area

InSAR velocity field across the North Anatolian Fault (eastern Turkey): Implications for the loading and release of interseismic strain accumulation

International audienceWe use the Persistent Scatterer Interferometric Synthetic Aperture Radar (PS-InSAR) technique with the European Space Agency's Envisat and ERS SAR data acquired on three neighboring descending tracks (T350, T078, and T307) to map the interseismic strain accumulation along a ~225 km long, NW-SE trending section of the North Anatolian Fault that ruptured during the 1939, 1942, and 1943 earthquakes in eastern Turkey. We derive a line-of-sight velocity map of the region with a high spatial resolution and accuracy which, together with the maps of earthquake surface ruptures, shed light on the style of continental deformation and the relationships between the loading and release of interseismic strain along segmented continental strike-slip faults. In contrast with the geometric complexities at the ground surface that appear to control rupture propagation of the 1939 event, modeling of the high-resolution PS-InSAR velocity field reveals a fairly linear and narrow throughgoing shear zone with an overall 20 ± 3 mm/yr slip rate above an unexpectedly shallow 7 ± 2 km locking depth. Such a shallow locking depth may result from the postseismic effects following recent earthquakes or from a simplified model that assumes a uniform degree of locking with depth on the fault. A narrow throughgoing shear zone supports the thick lithosphere model in which continental strike-slip faults are thought to extend as discrete shear zones through the entire crust. Fault segmentation previously reported from coseismic surface ruptures is thus likely inherited from heterogeneities in the upper crust that either preexist and/or develop during coseismic rupture propagation. The geometrical complexities that apparently persist for long periods may guide the dynamic rupture propagation surviving thousands of earthquake cycles

Cutaneous Findings in Patients with Acromegaly

Background: Acromegaly is a systemic syndrome caused by overproduction of growth hormone. The syndrome affects cutaneous, endocrine, cardiovascular, skeletal, and respiratory systems. Cutaneous manifestations of acromegaly are various, usually being the first presenting findings of the disease. Methods: Dermatological examinations of 49 patients of acromegaly who were followed-up at a tertiary referral hospital.Results: The study included 27 (55.1%) female and 22 (44.9%) male patients. The onset age of the disease was older in females than males (P =0.045). Most of the patients had acral enlargements, large triangular nose, coarse face, thickened lower lip, and prognathism. Fourteen patients (28.6%) had multiple cherry angiomas, 5 (10.2%) had varicose veins in lower limbs, and 2 (4.1%) had psoriasis.Conclusion: A wide spectrum of cutaneous symptoms and features may be associated with acromegaly. A detailed dermatological examination of patients with acromegaly should be an essential component of systemic evaluation. Future prospective studies investigating the relationships between changes in skin signs, hormone levels, and response to treatments may help to understand the details of skin involvement in acromegaly.</p

Becker nevus syndrome presented with ipsilateral breast hypoplasia

Becker nevus syndrome (BNS) is a rare epidermal nevus syndrome characterized with Becker nevus and ipsilateral breast gland hypoplasia or other skin, skeletal and/or muscle tissue disorders. A 24-year-old woman presented with brown, irregular bordered patch with a diameter of approximately 10 cm which consisted of several small macules on the left breast skin. The ultrasonography and magnetic resonance imaging revealed left breast hypoplasia. Histopathological examination demonstrated minimal acanthosis, papillomatosis, increase in basal layer melanin and hypertrophy of the erector pili muscle. Immunohistochemical staining was positive for androgen in the epidermis, dermal stromal cells and skin appendages. Depending on the clinical and histopathological findings, the patient was diagnosed as BNS. Diagnosis of BNS needs careful examination of pigmented macules and patches since non-hairy BN may be easily overlooked. Patients with BN should be evaluated for associated abnormalities of BNS, in which the severity and extend of ectodermal involvement may differ from patient to other

Onset of aseismic creep on major strike-slip faults

International audienceUnderstanding the behavior of active faults in response to tectonic stresses is a critical issue in earthquake physics and seismic hazard assessments (Carpenter et al., 2011). While most active faults are unstable and move abruptly, releasing in seconds to a few minutes the strain accumulated around them for decades to centuries, some faults slip continuously, storing little or no strain and are therefore considered to be unlikely to produce signifi cant earthquakes as long as this behavior persists (Bürgmann et al., 2000). Although aseismic fault creep was fi rst reported over half a century ago along some major plate boundary faults, including the San Andreas fault in California (United States) and the North Anatolian fault in Turkey, the origin and physical processes of fault creep remain subjects of debate (Schleicher et al., 2010). Two primary, complementary, and competing mechanisms have been proposed to explain the mechanics of aseismic fault creep: (1) the presence of weak mineral phases such as clay and phyllosilicates in the bulk composition of fault zones (Carpenter et al., 2011) or the formation of highly localized, phyllosilicate-rich interconnected networks of shear planes or foliations (Collettini et al., 2009) via chemical and mechanical processes, and/ or (2) trapped fl uid overpressures within fault zones (Byerlee, 1990). Although recent observations (Lockner et al., 2011) support the idea that aseismic creep is controlled by the presence of weak rocks in the fault zone rather than by high fl uid pressures, analysis of rock samples from active (Holdsworth et al., 2011) and exhumed (Warr and Cox, 2001) fault zones suggests that transient fl uid overpressures do occur in many fault zones and are most likely generated during coseismic faulting due to shear heating, low per-meability, high water content, and low strength of clay-rich shear zones. Whether due to mineralogy and/or fl uid pressure affects, how or when stable aseismic surface creep initiates on active faults remains uncertain. The fact that creeping segments of the North Anatolian fault at Ismetpasa and the San Andreas fault in the San Francisco Bay area also rupture coseismically suggests to us that fault creep may be initiated as postseismic after-slip (Çakir et al., 2005; Schmidt et al., 2005), a mechanism that could not be confi rmed previously due to the lack of pre-and post-earthquake observations on these fault sections. In this study we use space geodetic data and recent fi eld observations along the A.D. 1999 Izmit earthquake rupture (Fig. 1) to demonstrate continuing afterslip that appears to grade into steady-state creep on a >60-km-long segment of the Izmit coseismic fault, supporting seismic slip as one of the possible mechanisms for initiating steady-state creep on mature strike-slip faults. THE 1999 IZMIT EARTHQUAKE The M w 7.4 Izmit earthquake on 17 August 1999 occurred on the North Anatolian fault

Pili Annulati With Fragility: Electron Microscopic Findings Of A Case

Pili annulati (PA) is typically characterized by shinny beads seen along the hair shaft. PA is accepted to belong to the classification of hair shaft abnormalities without fragility. Herein, we described a 14-year-old, fair skin with dark-haired girl diagnosed as PA with fragility which was demonstrated by weathering features in electron microscopic examinations. The patient had shinny beaded, easily breakable hairs since the age of four. A few broken hairs were observed by a light pull test. Transmitted light microscopy revealed periodic dark bands in the hair shaft. These dark bands disappeared after application of 10% aqueous potassium hydroxide. Multiple cavities within hair shaft and severe cuticular damages representing the weathering pattern were observed in electron microscopic examinations. All these findings were found to be consistent with presence of fragility in PA. This case provides evidences of fragile hair structure of PA which may be due to pathological cavities within hair shafts.PubMe

The oxidant and antioxidant status in pityriasis rosea

Background: Pityriasis rosea (PR) is usually an asymptomatic and self-limiting papulosquamous skin disease with acute onset. The etiology has not been clarified yet. Recently, increased oxidative stress was found to play a role in etiopathogenesis of multiple cutaneous diseases with T cell-mediated immune response. However, there are no studies demonstrating the oxidative stress status in PR. Aim: The aim of the study is to determine the status of oxidative stress (OS) and paraoxonase (PON) 1/arylesterase enzyme activities in PR. Materials and Methods: Study included 51 patients with active PR lesions, and 45 healthy volunteers. Serum levels of total oxidant status (TOS), total antioxidant status (TAS), and PON1/arylesterase (ARES) activity were determined and oxidative stress index (OSI) was calculated in all patients and controls. Results: TAS levels and ARES activities in the patient group were significantly lower than the control group. On the other hand, TOS and OSI levels were significantly higher in patients compared with controls. There was no significant correlation between the duration of disease and TAS, TOS, OSI levels, and ARES activities. Conclusion: A systemic oxidative stress exists in PR, which suggests that OS may be involved in the etiopathogenesis of disease

Toll-like receptor expression in monocytes in patients with chronic kidney disease and haemodialysis: relation with inflammation

Background. Inflammation is one of the main contributors to atherosclerosis in haemodialysis (HD) patients. Activation of Toll-like receptors (TLRs) leads to inflammatory response. In this study, we aimed to evaluate the expression of TLRs on monocytes and relate their expression with inflammation in chronic kidney disease (CKD) and HD patients. Methods. Thirty-four age- and gender-matched controls and stage 3-4 CKD patients and thirty-two HD patients were included in each study group. The effect of HD on the expression of Toll-like receptor-2 (TLR-2) and Toll-like receptor-4 (TLR-4) on CD14(+) monocytes was determined at the beginning (baseline), during (120 min) and following (300 min and 24 h) HD and compared with control and stage 3-4 CKD groups. The HD procedure was performed by using low-flux polysulphone dialysers. In addition, serum IL-6 levels were evaluated in both groups at baseline and after a HD session. Results. The percentage of CD14(+) monocytes expressing TLR-2 were similar in all of the study groups, whereas the percentage of CD14(+) monocytes expressing TLR-4 were significantly lower in both stage 3-4 CKD and HD patients at baseline than in controls. The mean fluorescence intensities (MFI) of TLR-2 were significantly lower in controls than in stage 3-4 CKD and HD patients at baseline. The MFI of TLR-4 was similar in all of the groups. The percentage of CD14(+) monocytes expressing TLR-2 did not change during and after HD. The MFI of TLR-2 decreased at 120 min of HD compared with baseline (1837 +/- 672 vs 1650 +/- 578, P < 0.05), and recovered back to baseline values at 300 min and at 24 h post-HD. MFI of TLR-4 increased at 24 h compared with baseline (941 +/- 294 vs 1087 +/- 441, P < 0.05). Serum IL-6 levels correlated with MFI of TLR-2 and TLR-4 in stage 3-4 CKD patients and in HD patients at baseline and after HD in univariate analysis. Stepwise multiple regression analysis revealed that MFI of TLR-2 was an independent determinant of serum IL-6 concentrations in stage 3-4 CKD and in HD patients at baseline, at 300 min and at 24 h post-HD. Conclusions. Our study demonstrates that TLR-2 is associated with the inflammatory response of non-dialysed and dialysed CKD patients