Increase of landslide activity after a low magnitude earthquake inferred by DInSAR interferometry

On August 16th, 2018, an Mw 5.1 earthquake struck the Molise region (central Italy), inducing 84 earthquake-triggered landslides that involved soil covers of clayey materials and flysch on gently-dip slopes predominantly. To quantify the spatio-temporal landslide activity in the months immediately after the earthquake, a Differential SAR Interferometry (DInSAR) analysis was carried out in a time span comprising two years before the earthquake and one followed, recognising both first-time and reactivated landslides. The results showed a clear increase in landslide activity following the low magnitude earthquake occurrence with respect to the one recorded in the same months of the previous years. Several coherent landslides (earth slides and earth flows) were observed following the seasonally recurrent rainfall events. Such an increase was observed for both reactivations and first-time landslides, showing a decrease of inactivity period as well as activity over wider periods. Furthermore, spatial density distribution of the landslides was investigated in the post-seismic time along transepts perpendicular and parallel to the direction of the tectonic element responsible for the seismic event, respectively. An asymmetrical distribution was deduced parallel to the fault strike with the higher number of landslides located inside the compressional sector according to a strike-slip faulting mechanism.

SUBSURFACE STRUCTURE OF BATURAGUNG ESCARPMENT REVEALED THROUGH THREE-DIMENSIONAL GRAVITY INVERSION

Baturagung Escarpment is an essential tectonic element of Java Island because it represents a transition from the Southern Mountain Block to the Kendeng Basin. This study has succeeded in producing a three-dimensional model of the Baturagung Escarpment subsurface using gravity anomaly data. The data are distributed along a regional scale transect, whose resolving capability has been tested using a checkerboard test. Our proposed geophysical model can fit the observed data very well, with a 0.77% RMS error. This model exhibits a structural depression bounded by high basement blocks below the Baturagung Escarpment, one of the basement block outcrops at Jiwo Hills. The maximum width of the depression is 10 km, with a depth exceeding 3 km in some places. The depression might be formed because of an extensional tectonic regime that prevailed during the Palaeogene, followed by volcanic arc loads' emplacement up to the early Miocene.

Neotectonic activity in Lake Sils (Engadine, Switzerland) as trigger of tsunamigenic delta collapses?

<p>Tsunamigenic delta collapses in lacustrine environments are still poorly understood phenomena in terms of their recurrence rate, driving mechanism and hazard potential. A partial collapse of the Isola Delta in Lake Sils (Engadine, Switzerland) with an estimated depositional volume of at least 6.5 million m<sup>3</sup> is radiocarbon-dated to 548-797 cal CE and may represent a typical tsunamigenic delta collapse in the Alpine environment. Recent studies propose that this basin-wide tsunami with a run-up height of 2–3 m and an inundation distance of 200 m at the lakeshore highlights the importance to better understand these processes and the associated hazards. The collapse was likely triggered by a strong regional earthquake responsible for several simultaneously triggered mass movements in nearby Lake Silvaplana and Lake Como. Increasingly available datasets from Lake Sils (short cores, high-resolution seismic reflection data, numerical tsunami simulations) are now complemented by multibeam swath bathymetry, providing a high-resolution (1 m grid) model of the lake floor that offers new insights into the failed slope masses, and post-failure basin morphology.</p><p>Lake Sils is located in the Upper Engadine in southeastern Switzerland at ~1800 m above sea level and has four major sub-basins (Maloja, Central, Sils & Lagrev Basins). A major tectonic element is the Engadine Fault Line (EFL), an oblique sinistral strike-slip fault that runs along the entire Upper Engadine valley. Its influence on the subaqueous morphology of the Maloja Basin in Lake Sils is expressed in the form of several localized troughs and ridges. It is suspected that the fault also cross-cuts the Isola Delta, possibly causing renewed delta failures in case of reactivation. In fact, recent studies have indicated that there is strong evidence for Quaternary left-lateral transcurrent faulting of the EFL, e.g. offsetting a river gully in the Forno Valley close to Lake Sils.</p><p>New bathymetric data from Lake Sils and their morphologic interpretations indicate subaquaeous slope failures, the extent of the Isola Delta collapse, and several trough-ridge features within the southwestern Maloja Basin. The latter are possibly indicative of ongoing faulting in the region since such features strongly suggest rhomboidal pull-apart basins within the Maloja Basin along the EFL. In general, such localized troughs within a lacustrine system are expected to level-out over time due to higher sedimentation rates in preferentially deeper regions of the lake. This study thus highlights the use of high-resolution bathymetric data in identifying the combined effects of deep-seated tectonic zones with shallow lake-floor processes, providing new insights into lacustrine hazard studies.</p>

Morphotectonic aspects in a part of Naga-Schuppen belt, Assam-Nagaland region, Northeast India

The Belt of Schuppen is an important tectonic element of the Assam-Arakan basin. It is a narrow belt of thrust slices in southeastern boundary of the Assam valley. The Naga Schuppen Belt, consisting of eight or more imbricated thrusts, occurs between the Naga and Disang thrusts. This present study encompasses an area of 4,720 sq km along the Assam-Nagaland border. The Dikhow River, which is a seventh order basin, originates from Naga Hills flowing through a total length of 240 km in the Assam valley and reaches the Brahmaputra. In this study, the morphotectonic analysis of the Dikhow River was carried out to understand the role of active tectonics of the Naga Hills in Nazira-Naginimora areas of Assam and Nagaland respectively. The parameters such as asymmetric factor (AF), transverse topographic symmetric factor (T), and stream length gradient index (SL) were computed. Absolute AF values shows asymmetric to highly asymmetrical shape of the basins (range III-IV) which is also supported by T values. Anomalous SL values were obtained wherein major lineament and tectonic features are present. This indicates that the study area is tectonically active. Further, in the Assam valley it has been observed in the bank stratigraphy of Dikhow River that the Quaternary sediments are deformed. This deformation of the soft older alluvium indicates that the area is undergoing deformation during post Pliocene time. This evidence demands the morphotectonic evaluation of the aforesaid area to demarcate the tectonic activeness of the region in post Pliocene times.

Nucleation and amplification of doubly-plunging anticlines: the Butkov pericline case study (Manín Unit, Western Carpathians)

The Manín Unit represents a transitional tectonic element between the Central Western Carpathians and the Pieniny Klippen Belt. The overall map-view structure of the Manín Unit is dominated by elliptical antiforms composed of comparatively competent Jurassic and Lower Cretaceous strata, surrounded by soft Upper Cretaceous shales, marls and sandstones. During layer-parallel shortening, the Manín sedimentary succession behaved as a multilayer reinforced by a variously thick rigid layer of massive Urgonian limestone. The multilayer deformed by flexural slip folding, but the fold wavelength was controlled by the rigid layer undergoing buckling. It is inferred that, besides the lateral thickness differences in the rigid layer, development of brachyfolds and particularly periclines such as the Butkov fold also resulted from the interference of two perpendicular macroscopic fold systems.

Mies van der Rohe: Cuba 1957 - Berlin 1968. Il compimento della “nuova” arte del costruire | Mies van der Rohe: Cuba 1957 - Berlin 1968. The fulfillment of the “new” art of building

L’arte del costruire (Baukunst) del nostro tempo trova fondamento nella ricerca di una nuova forma di composizione dei differenti autonomi elementi costruttivo/figurativi, nei quali risulta originariamente frammentata e stratificata: l’elemento plastico murario, che si occupa della fondazione del suolo, come massa stereotomica topograficamente modellata in rapporto alla conformazione del luogo; l’elemento propriamente tettonico della struttura di sostegno del riparo, strettamente riferibile ai procedimenti di montaggio di elementi finiti; l’elemento, portatore di motivi tessili, dell’involucro che dà forma allo spazio interno: pura superficie di rivestimento (Bekleidung) tendente alla smaterializzazione. Questi elementi si sono definiti attraverso un lungo processo di formazione, a partire dalla radicale revisione teorica delle tradizionali categorie tettoniche, nel corso dell’Ottocento. Essi sembrano trovare compimento nell’ultima fase della ricerca miesiana della “nuova” arte del costruire, nel progetto della Halle monumentale per Cuba/Berlin (1957-68).KEYWORDS: Mies van der Rohe; tettonica; spazio; struttura; costruzione; Baukunst.The art of building (Baukunst) of our time is founded on the search of a new kind of composition of different autonomous elements, in which it was originally fragmented and stratified: the plastic masonry element of the earthwork, as a stereotomic, topographic mass, closely related to the specific site; the properly tectonic element of the light carpentry framework/roofwork, largely connected to the rational modularity of assembly technique; the dematerialized element of spatial enclosure, as textile cladding surface: the pure dressing (Bekleidung). These elements have been defined through a long form-giving process, started with the radical nineteenth-century theoretical review of traditional tectonic categories. The same elements seem to reach their fulfillment in the last phase of Mies’ research on the “new” art of building: the project for a monumental Halle in Santiago de Cuba, finally built in Berlin (1957-68).KEYWORDS: Mies van der Rohe; tectonics; space; structure; construction; Baukunst.

TECTONIC EVOLUTION OF THE GIPPSLAND BASIN AND HYDROCARBON POTENTIAL OF ITS LOWER CONTINENTAL SHELF

Tectonic evolution of the Gippsland Basin, par­ticularly for the 120 to 66 Ma period, is reviewed based on the interpretation of BMR Continental Mar­gin Seismic data and industry seismic and well infor­mation over the continental shelf. It is revealed that the eastern limit of the Early Cretaceous (120-97 Ma) rift is the Gippsland Rise—a new tectonic element. The Rise is part of a regional deep-seated metamor­phosed Palaeozoic lineament belonging to the Tasman Fold Belt upon which the Strzelecki Group onlapped from the west. Two newly-identified transfer fault zones named here, the Eastern Gippsland Margin Transform and the Cape Everard Transfer Fault, bound the rise from the east and the west respectively.In a second phase of rifting (97-80 Ma) the following tectonic events took place:A narrower rift was incised at the onset of this phase parallel to the initial rift; The Gippsland Rise became unstable;A new NW-SE tensional regime commenced;The Southern Platform collapsed (in the Cenomanian) and the Southern Ocean accessed the three Bass Strait basins; Towards the end of this episode (in the Campanian) the Southern Platform and the Gippsland Rise emerged, andThe Northern and Southern Grabens (new names) were incised in the Gippsland Rise connecting the newly formed Tasman Sea to the basin.Ingredients necessary for potential hydrocarbon exploration in the lower shelf and upper slope such as source, reservoirs, seal, trapping mechanism and re­charge do exist but require additional seismic and geological evaluation.