Characteristics and outcomes of fetal ventricular aneurysm and diverticulum: combining the use of a new technique, fetal HQ

ObjectivesCongenital ventricular aneurysms or diverticulum (VA/VD) are rare cardiac anomalies with lack prenatal evaluation data. The present study aimed to provide the prenatal characteristics and outcomes from a tertiary center and the use of new techniques to evaluate the shape and contractility of these fetuses.MethodsTen fetuses were diagnosed with VA or VD, and 30 control fetuses were enrolled. Fetal echocardiography was performed to make the diagnosis. The prenatal echo characteristics and follow-up data were carefully reviewed. The shape and contractility measurements of the four-chamber view (4CV) and both ventricles were measured and computed using fetal fetal heart quantification (HQ).ResultsA total of 10 fetuses were enrolled, including 4 cases of left ventricular diverticulum, 5 cases of left ventricular aneurysm, and 1 case of right ventricular aneurysm (RVA). Four cases chose to terminate the pregnancy. The RVA was associated with a perimembranous ventricular septal defect. Two cases had fetal arrhythmia, and one case had pericardial effusion. After birth, one case underwent surgical resection at five years old. The 4CV global sphericity index (SI) of free-wall located ventricular outpouching (VO) was significantly lower than the apical ones and the control group (p < 0.01). Four of five apical left VOs had significant higher (>95th centile) SI in base segments, and three of four left VOs in the free-wall had significant lower (< 5th centile) SI in the majority of 24 segments. Compared to the control group, the left ventricle (LV) global longitudinal strain, ejection fraction, and fractional area change were significantly decreased (p < 0.01), while the LV cardiac output of the cases was in the normal range. The transverse fraction shortening of the affected segments of ventricles was significantly lower than the other ventricle segments (p < 0.01).ConclusionsFetal HQ is a promising technique to evaluate the shape and contractility of congenital ventricular aneurysm and diverticulum

Discrete Element Modeling of a Subduction Zone with a Seafloor Irregularity and its Impact on the Seismic Cycle

peer reviewedSeafloor irregularities influence rupture behavior along the subducting slab and in the overriding plate, thus affecting earthquake cycles. Whether seafloor irregularities increase the likelihood of large earthquakes in a subduction zone remains contested, partially due to focus put either on fault development or on rupture pattern. Here, we simulate a subducting slab with a seafloor irregularity and the resulting deformation pattern of the overriding plate using the discrete element method. Our simulations illustrate the rupture along three major fault systems: megathrust, splay and backthrust faults. Our results show different rupture dimensions of earthquake events varying from tens to ca. 140 km. Our results suggest that the recurrence interval of megathrust events with rupture length of ca. 100 km is ca. 140 years, which is overall comparable to the paleoseismic records at the Mentawai area of the Sumatran zone. We further propose the coseismic slip amounts decrease and interseismic slip amounts increase from the surface downwards gradually. We conclude that the presence of seafloor irregularities significantly affects rupture events along the slab as well as fault patterns in the overriding plate

Discrete element modeling of continental deformation and volcanic spine extrusion

The India-Asia collision zone is an example of the largest present day continental deformation, which started about 55 Ma ago. Previous unscaled 2D modeling of such deformation did not address either the growth of topographic relief or localized faulting. Here, we use the YADE Discrete Element Method (DEM) code to produce a suite of scaled 3D models of the collision. They generate two plate-scale strike-slip faults that extrude and rotate large coherent blocks. The locations, lengths, ages and offsets of the model faults are in keeping with those of the Red River and Altyn Tagh mega faults, east and north of Tibet. The model also generates plateaus similar to Tibet. Repetitive volcanic seismic events often occur at roughly constant depth, in swarms, beneath actively extruding domes or spines. Using the DEM approach and focal mechanisms during Mount St. Helens 2004-2006 eruptions, we show that necking and fracking/degassing of magma explains such seismicity.​Doctor of Philosophy (ASE

Space Imaging Geodesy Reveals Near Circular, Coseismic Block Rotation During the 2016 M<SUB>w</SUB> 7.8 Kaikōura Earthquake, New Zealand

International audienceLarge earthquakes usually rupture plate boundary faults, releasing the accumulated stress as displacements localized along smooth, narrow faults. However, certain earthquakes initiate off main faults, rupturing adjacent, secondary faults. The mechanisms of such atypical stress release remain enigmatic, partly due to a lack of detailed geodetic evidence. Here using the 3D coseismic displacement field derived from space imaging geodesy, we detect 10-km-scale, nearly-circular coseismic block rotation during the 2016 Mw 7.8 Kaikōura earthquake in New Zealand. Together, geodetic observations, longer term local paleomagnetic data, analytical, and discrete element modeling imply that localized block rotation occurred south of the Hope fault along weak, steep, bedding-parallel boundaries within a narrow, ~20-km-wide dextral shear zone. That stress near plate boundary faults can be partially released in zones of distributed ruptures absorbing coseismic rotation may retard rupture along main faults. Our observations also suggest that coseismic rotation may help accomodate plate boundary propagation

The shape of the Himalayan "Arc": An Ellipse pinned by syntaxial strike-slip fault tips

&lt;p&gt;The Python code and C++ files are for the set-up of the model. The model setup and model engine settings are in the file "&lt;a href="../api/records/10442255/draft/files/indenter_file.py/content" target="_blank" rel="noopener noreferrer"&gt;indenter_file.py&lt;/a&gt;". The model parameters are in the file "&lt;a href="../api/records/10442255/draft/files/parameter.Table/content" target="_blank" rel="noopener noreferrer"&gt;parameter.Table&lt;/a&gt;".&nbsp;"&lt;a href="../api/files/7fd17d70-ad1d-4b05-9251-3a52f0e6d4e2/LPlasPM.cpp?versionId=bf8367f6-fb07-4327-9cbb-1b00ae97834d"&gt;LPlasPM.cpp&lt;/a&gt;" implements the constitutive law. After downloading the source code YADE from http://www.yade-dem.org/, follow the instructions from the web to install YADE, put cpp files into the YADE source folder, and compile them. Run "yade-batch parameter.Table indenter_file.py" in the Ubuntu system. Then, use Paraview (downloading from https://www.paraview.org/) to see the results of the model.&nbsp;&lt;/p&gt

Discrete Element Modeling of Southeast Asia's 3D Lithospheric Deformation During the Indian Collision

International audienceAbstract The Indian collision has deformed the eastern Asian continent in a multifaceted way, uplifting Tibet and surrounding mountains, activating ≥1,000 km‐long strike‐slip faults, and opening Tertiary rifts and oceanic basins up to ≈3,000 km away from the Himalayas. Modeling such broad‐scale tectonics has been challenging. While continent‐scale, lithospheric deformation appears to have been primarily taken‐up by long, narrow, inter‐connected shear‐zones with large offsets, the contribution of processes such as channel‐flow, collapse, delamination, etc… has remained contentious. Here, based on increasing 4 G (Geological, Geophysical, Geochronological, Geodetic) evidence including kinematic and timing constraints on the main mechanisms at play, we use Discrete Element (DE) Modeling to simulate and further understand the evolution of 3D strain across east Asia since the onset of collision, ≈55 Ma ago. The planar, 50 million km 2 , 125 km‐thick models are scaled for gravity. The approach permits mega‐fault generation and evolution without pre‐arranged initial settings. The results provide insight into fault birth, propagation and motion, as well as mountain building and plateau growth. They corroborate that continental crustal thickening across Tibet alternated with the extrusion of large blocks that rifted apart in the far field. Remarkably, without changes in boundary conditions or indentation rate, the DE model also vindicates slip reversal along initial strike‐slip shear zones

Assessing the brittle crust thickness from strike-slip fault segments on Earth, Mars and Icy moons

International audienceSegment lengths along major strike-slip faults exhibit a size dependency related to the brittle crust thickness. These segments result in the formation of the localized “P-shear” deformation crossing and connecting the initial Riedels structures (i.e. en-echelon fault structures) which formed during the genesis stage of the fault zone. Mechanical models show that at all scales, the geometrical characteristics of the Riedels exhibit dependency on the thickness of the brittle layer. Combining the results of our mechanical discrete element model with several analogue experiments using sand, clay and gypsum, we have formulated a relationship between the orientation and spacing of Riedels and the thickness of the brittle layer. From this relationship, we derive that for a pure strike-slip mode, the maximum spacing between the Riedels is close to three times the thickness of the layer. For a transtensional mode, as the extensive component becomes predominant, the spacing distance at the surface becomes much smaller than the thickness. Applying this relationship to several well-characterized strike-slip faults on Earth, we show that the predicted brittle thickness is consistent with the seismogenic depth. Supposing the ubiquity of this phenomenon, we extented this relationship to characterize en-echelon structures observed on Mars, in the Memnonia region located West of Tharsis. Assuming that the outer ice shells of Ganymede, Ence-ladus and Europa, exhibit a brittle behavior, we suggest values of the corresponding apparent brittle thicknesses