Ground deformation measurements over Lake Trichonis based on SAR interferometry.

Ο σκοπός της παρούσας μελέτης είναι o εντοπισμός της παραμόρφωση του εδάφους στην ευρύτερη περιοχή της Λίμνης Τριχωνίδας (Δυτική Ελλάδα), εστιάζοντας κυρίως στο σεισμικό φαινόμενο του Απριλίου 2007 με την σμήνοσειρά σεισμών που σημειώθηκε στην περιοχή της λίμνης. Η περιοχή συνιστά μία pull-apart λεκάνη, η οποία παρουσιάζει γενικότερα μία έντονη σεισμική δραστηριότητα λόγο των δύο ενεργών ρηγμάτων κατά μήκος του βόρειου και νότιου περιθωρίου της. Η σμηνοσειρά ξεκίνησε με μικρού μεγέθους σεισμούς, στις 9 Απριλίου 2007 ενώ ακλούθησαν τρία ισχυρότερα σεισμικά γεγονότα στις 10 Απριλίου 2007, με μεγέθη που κυμαίνονται από 5,0 έως 5,2 Mw, τα οποία και αποτέλεσαν τα μεγαλύτερα ολόκληρης της ακολουθίας. Η σεισμική δραστηριότητα συνεχίστηκε για περισσότερο από ένα μήνα με μικρότερα σεισμικά γεγονότα. Βάσει των σεισμολογικών δεδομένων οριοθετήθηκαν δύο νέα κανονικά ρήγματα ΒΔ-ΝΑ διεύθυνσης κατά μήκος της νοτιοανατολικής όχθης της λίμνης. Χρησιμοποιώντας ένα σύνολο 28 εικόνων Ραντάρ, του δορυφόρου ENVISAT για την περίοδο από το Φεβρουάριο του 2003 μέχρι τον Φεβρουάριο του 2010 εφαρμόστηκε η τεχνική της διαφορικής συμβολομετρίας και πιο συγκεκριμένα διαφορετικές τεχνικές σώρευσης συμβολογραφημάτων με σκοπό την ανίχνευση και χαρτογράφηση των παραμορφώσεων του εδάφους που προκλήθηκε από την «σμηνοσειρά σεισμών». Σύμφωνα με τα αποτελέσματά των συγκεκριμένων τεχνικών αποδεικνύεται ότι η περιοχή παρουσιάζει εντελώς διαφορετικό καθεστώς εδαφικής παραμόρφωση κατά τη διάρκεια της προ-σεισμικής και μετα-σεισμικής περιόδου σε σχέση με την συν-σεισμική.The aim of this study is to detect and measure ground deformation over the broader area of Lake Trichonis (Western Greece), focusing mainly on the April 2007 earthquake swarm which occurred at the vicinity of the Lake. The area, forming a pull-apart basin, presented historically an intense seismic activity along the two active normal faults at the northern and southern part of the Lake. The swarminitiated by small magnitude events on the 8th of April 2007 followed by the three strongest events of the entire sequence on the 10th of April 2007, with magnitudes ranging from 5.0 to 5.2 Mw. The seismic activity continued for longer with smaller seismic events. Based on seismological data this activity was attributed to two unmapped NW SE trending normal faults that bounds the SE bank of the Lake. Using a dataset of 28 ENVISAT ASAR scenes covering the period from February 2003 until February 2010 (~7 yr), different Interferometric Stacking techniques was applied in order to quantify the ground deformation induced by the earthquake swarm as well as its effect on the inter-seismic deformation pattern of the area. Our results indicate that co-seismic motion differs significantly from that observedduring the pre- and post- swarm periods. The co-seismic pattern reveals subsidence at the northern and uplift at the southern lake sides, consistent with the structural model already proposed for the area. For the pre- and post-seismic periods both sides of the Lake show stability or low rates of subsidence with higher deformationvelocity rates for the period after the seismic activity, possibly attributed to postseismic relaxation. Our findings imply that inter-seismic ground deformation does not necessary follow the deformation pattern observed during seismic triggering, thus, long-term geodetic observations such as those provided by SAR interferometry are valuable in order to fully characterize the geodynamic behavior of an active region

SHORT PERIOD CHANGE DETECTION OF SPERCHIOS LOWER DELTA AREA USING SPACE RADAR IMAGES

Being highly dynamic by nature, due to their changing hydrological regime and to the encroachment of urbanization, industrialization and changing patterns in agriculture, reliable and timely information of coastal areas is a prerequisite for their effective management. The aim of this paper is to assess the use of ERS-2 SAR satellite data to detect short period changes in the case of the R. Sperchios coastal area that is located at the eastern part of the Maliakos Gulf (near the middle of the east coast of the Greek mainland). A Landsat 7 (ΕΤΜ+) image served as a reference for the interpretation of the ERS images. In order to highlight and detect the changes occurred in the study area two methods were applied. The first method is based on the creation of a Temporal Differentiate Image, consisted of the three ERS-2 images (Figure 1). The second method concerns the implementation of Principal Component Transform (PCT) on the three multitemporal scenes. The final images derived from the two different methods were compared and evaluated. Both methods didn't show any significant change along the coastline. PCT method illustrates more clearly the seasonal changes of crops in the lower delta area. Eventually, radar technology gave the opportunity to discriminate shallow areas, which does not appear in satellite optical data. Concurrently, the effect of wind direction was investigated

Subaortic and midventricular obstructive hypertrophic cardiomyopathy with extreme segmental hypertrophy

BACKGROUND: Subaortic and midventricular hypertrophic cardiomyopathy in a patient with extreme segmental hypertrophy exceeding the usual maximum wall thickness reported in the literature is a rare phenomenon. CASE PRESENTATION: A 19-year-old man with recently diagnosed hypertrophic cardiomyopathy (HCM) was referred for sudden death risk assessment. The patient had mild exertional dyspnea (New York Heart Association functional class II), but without syncope or chest pain. There was no family history of HCM or sudden death. A two dimensional echocardiogram revealed an asymmetric type of LV hypertrophy; anterior ventricular septum = 49 mm; posterior ventricular septum = 20 mm; anterolateral free wall = 12 mm; and posterior free wall = 6 mm. The patient had 2 types of obstruction; a LV outflow obstruction due to systolic anterior motion of both mitral leaflets (Doppler-estimated 38 mm Hg gradient at rest); and a midventricular obstruction (Doppler-estimated 43 mm Hg gradient), but without apical aneurysm or dyskinesia. The patient had a normal blood pressure response on exercise test and no episodes of non-sustained ventricular tachycardia in 24-h ECG recording. Cardiac MRI showed a gross late enhancement at the hypertrophied septum. Based on the extreme degree of LV hypertrophy and the myocardial hyperenhancement, an implantation of a cardioverter-defibrillator was recommended prophylactically for primary prevention of sudden death. CONCLUSION: Midventricular HCM is an infrequent phenotype, but may be associated with an apical aneurysm and progression to systolic dysfunction (end-stage HCM)

Ground deformation detection of the greater area of Thessaloniki (Northern Greece) using radar interferometry techniques

In the present study SAR interferometric techniques (stacking of conventional interferograms and Permanent Scatterers), using images from satellites ERS-1 and 2, have been applied to the region of Thessaloniki (northern Greece). The period covered by the images is 1992–2000. Both techniques gave good quantitative and qualitative results. The interferometric products were used to study ground surface deformation phenomena that could be related to the local tectonic context, the exploitation of underground water and sediments compaction. <br><br> The city of Thessaloniki shows relatively stable ground conditions. Subsidence in four locations, mainly in the area surrounding the city of Thessaloniki, has been detected and assessed. Two of the sites (Sindos-Kalochori and Langadhas) were already known from previous studies as subsiding areas, using ground base measurements. On the contrary the other two sites in the northern suburbs of Thessaloniki (Oreokastro) and in the south-east (airport area) were unknown as areas of subsidence. A further investigation based on fieldwork is needed in these two areas. Finally, an attempt to interpret the observed deformation, according to the geological regime of the area and its anthropogenic activities, has been carried out

Risk factors for sudden cardiac death in hypertrophic cardiomyopathy

Aim of this study was the evaluation of six non invasive clinical indices as risk factors for sudden death (SD)in hypertrophic cardiomyopathy (HCM). Previous syncope, family history of SD, non sustained ventricular tachycardia, abnormalblood pressure response during exercise, excessive hypertrophy ≥3 cm and left ventricular outflow tract obstructionwith a peak gradient ≥30 mmHg were evaluated in a cohort of 166 patients(112 males, 51.8 ± 15.6 years), followed up for amedian of 32.4 months (range 1 to 209 months). During follow up 13 patients reached study’s endpoints: SD, cardiac arrest,documented sustained ventricular tachycardia and/or Implantable Cardioverter Defibrillator (ICD)-discharge. Patients havingexperienced syncope or presenting with a Maximum Wall Thickness ≥3cm in echocardiography were more sensitive to SDemergence since they had a 13.07 (95%CI: 4.00-46.95, p < 0.0001) and a 10.07 (95%CI: 2.92-34.79, p = 0.003) greater relativerisk respectively. In our cohort of patients only two of the six ‘recognised’ potential risk factors for SD were found sensitive,a result causing scepticism about the validity of criteria used for ICD implantation in HCM patients for SD prevention

Identification of high risk patients with hypertrophic cardiomyopathy in a northern Greek population

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Hypertrophic cardiomyopathy with midventricular obstruction and apical aneurysm formation in a single family: case report

<p>Abstract</p> <p>Background</p> <p>Hypertrophic cardiomyopathy (HCM) is an extremely heterogeneous disease. An under recognized and very often missed subgroup within this broad spectrum concerns patients with left ventricular (LV) apical aneurysms in the absence of coronary artery disease.</p> <p>Case presentation</p> <p>We describe a case of HCM with midventricular obstruction and apical aneurysm formation in 3 patients coming from a single family. This HCM pattern was detected by 2D-echocardiography and confirmed by cardiac magnetic resonance imaging. A cardioverter defibrillator was implanted in one of the patients because of non-sustained ventricular tachycardia detected in 24-h Holter monitoring and an abrupt drop in systolic blood pressure during maximal exercise test. The defibrillator activated 8 months after implantation by suppression of a ventricular tachycardia providing anti-tachycardia pacing. The patient died due to refractory heart failure 2 years after initial evaluation. The rest of the patients are stable after a 2.5-y follow-up period.</p> <p>Conclusion</p> <p>The detection of apical aneurysm by echocardiography in HCM patients may be complicated. Ventricular tachycardia arising from the scarred aneurysm wall may often occur predisposing to sudden death.</p