Geological-geotechnical risk mapping of gravitational mass movements in an urban area in Colombo, Brazil

This work presents a geological-geotechnical risk map of gravitational mass movements and a susceptibility map to shallow translational slides to Vila Nova community, located in the municipality of Colombo, Brazil. The first map was created through a qualitative mapping methodology and the second one was elaborated using a deterministic method of slope stability. An aerial photogrammetric survey with UAV technology was performed, as well as field reconnaissance, laboratory testing, and geoprocessing techniques. Seven slope failures were identified as well as a range of other evidences of instability associated with the predisposition of the terrain to erosive and gravitational movements linked to human intervention without urban planning and engineering techniques. Moreover, the qualitative and quantitative analyses pointed out that 13% to 9% of the study area, respectively, are in a very high-risk condition for landslides. Thus, the resulting cartographic products are presented as an important technical contribution for landslide risk management as well as land use planning for reducing the geotechnical problems faced on site.

Morphology of large-scale debris avalanche deposits in Cianjur Plains, West Java, Indonesia

Large-scale debris avalanche deposit (DAD) processes rarely occur, but the impact is catastrophic. Large-scale flank collapse from ancestral Gede volcano resulted in the deposition of debris avalanche deposits that manifested as prominent hummocky hill landforms covering 192 km2 of the Cianjur Plains, West Java, Indonesia. Although the deposit covers large areas and shows unique volcanic landscape morphology, studies on debris avalanche deposits are limited. Here, we show the results of field reconnaissance, satellite photography and digital elevation model analysis to understand the morphology of large-scale debris avalanche deposits, including their distribution and morphological characteristics. The interpreted thickness of the deposit ranges from 200-500 m, although the hummocky hill with a well-rounded texture is only 50-100 m high due to intense erosion in the tropical region with the remaining portion of the megaclast blocks buried. The distribution of hummocky hills indicates that the flow was constrained by the pre-existing basin configuration. The debris avalanche deposit shows fan-like morphology that characterizes block facies located near the fan mouth, while the matrix facies has matrix-supported smaller blocks in the distal part. The mouth of the debris avalanche deposit is located just south of Cianjur township, with the highest concentration of megaclast block as block facies, which is interpreted as the main depositional axis. The block facies apparently stopped by lineament of the SW-NE-oriented Cimandiri valley to the southeast and NNE-SSW-oriented Cisokan River lineament to the east, which was interpreted as a buried normal fault that was considered a barrier to confine the flow of block facies deposition.

Rapid Terrain Assessment for Earthquake-Triggered Landslide Susceptibility With High-Resolution DEM and Critical Acceleration

Earthquake ground motion often triggers landslides in mountainous areas. A simple, robust method to quickly evaluate the terrain’s susceptibility of specific locations to earthquake-triggered landslides is important for planning field reconnaissance and rescues after earthquakes. Different approaches have been used to estimate coseismic landslide susceptibility using Newmark’s sliding block model. This model requires an estimate of the landslide depth or thickness, which is a difficult parameter to estimate. We illustrate the use of Newmark sliding block’s critical acceleration for a glaciated valley affected by the 2015 Gorkha earthquake in Nepal. The landslide data came from comparing high-resolution pre- and post-earthquake digital elevation models (DEMs) derived from Spot 6/7 images. The areas where changes were detected provided an inventory of all the landslides triggered by the earthquake. The landslide susceptibility was modeled in a GIS environment using as inputs the pre-earthquake terrain and slope angles, the peak ground acceleration from the 2015 Gorkha earthquake, and a geological map. We exploit the depth information for the landslides (obtained by DEM difference) to apply the critical acceleration model. The spatial distribution of the predicted earthquake-triggered landslides matched the actual landslides when the assumed landslide thickness in the model is close to the median value of the actual landslide thickness (2.6 m in this case). The landslide predictions generated a map of landslide locations close to those observed and demonstrated the applicability of critical acceleration for rapidly creating a map of earthquake-triggered landslides.

The morphology of large-scale debris avalanche deposit in Cianjur plains, West Java, Indonesia

The large-scale debris avalanche deposit (DAD) process are quite rarely occurring but the impact is catastrophic. Large-scale flank collapse from ancestral Gede volcano resulted in the deposition of debris avalanche deposit that manifested as prominent hummocky hill landform covering 192 km2 area in Cianjur plains, West Java, Indonesia. Although the deposit covers large areas and showing unique volcanic landscape morphology, the study on the debris avalanche deposit is limited. Here we show the result of field reconnaissance, satellite photo and digital elevation model analysis to understand the morphology of large-scale debris avalanche deposit including distribution and morphological characteristics. The interpreted thickness of the deposit ranging from 200-500m, although the hummocky hill with well-rounded texture is only 50–100 m height due to intense erosion in the tropical region with the remaining portion of the megaclast blocks buried. The distribution of hummocky hills indicate that the flow constrained by pre-existing basin configuration. The debris avalanche deposit showing fan-like morphology that characterized block facies located near the fan mouth, while the matrix facies with matrix-supported smaller blocks in the distal part. The mouth of debris avalanche deposit located just south of Cianjur township with the highest concentration of megaclast block as block facies that interpreted as the main depositional axis. The block facies apparently stopped by lineament of SW-NE oriented Cimandiri valley to the southeast and NNE-SSW oriented Cisokan river lineament to the east which interpreted as buried normal fault that considered as the barrier to confine flow of block facies deposition.

Rapid Postearthquake Field Reconnaissance, Paleoseismic Trenching, and GIS-Based Fault Slip Variability Measurements along the Mw 6.4 and Mw 7.1 Ridgecrest Earthquake Sequence, Southern California

ABSTRACT Understanding fault rupture deformation patterns, especially in complex fault zones, has fundamental implications on seismotectonic studies and hazard mitigation for the built environment. The 2019 Mw 6.4 and Mw 7.1 Ridgecrest earthquake ruptures offer an opportunity to quantify deformation patterns and surface displacements from a complex fault rupture. Our field reconnaissance, within 18 hr of the Mw 6.4 event, documented a complex and relatively broad fault deformation zone up to a few kilometers wide in the vicinity of a gas transmission pipeline intersected by the surface rupture south of Highway 178. The subsequent Mw 7.1 event resulted in similarly distributed surface fault deformation within a broad zone that crossed a second gas transmission pipeline located south of Highway 178. On 10 July, fault-normal pipeline assessment trenches were excavated at both locations and provided evidence for late Pleistocene fault rupture on both faults expressed as upward fault truncations and paleoliquefaction features. Subsequent imagery-based rupture-mapping facilitated identification and measurement of offset features that were not identified during field mapping. Fault displacement measurements document a gradual decrease in fault slip on rupture southwestward from the Mw 6.4 epicenter within the study area. However, displacement along the primary Mw 7.1 rupture decreased more drastically southeastward toward a structural complexity at a fault stepover expressed as a horsetail splay. Fault-normal slip distributions showed that majority of the surface deformation was accommodated along discrete fault strands within the primary fault zone across both ruptures. This work expands the catalog of high-fidelity coseismic rupture information used to better understand seismotectonic processes, while contributing to refinement of fault displacement models used in support of critical infrastructure design.

Liquefaction field reconnaissance following the 29th December 2020 Mw 6.4 Petrinja earthquake (Croatia)

<p>Earthquakes and related coseismic effects at the surface, both primary and secondary, such as liquefaction and lateral spreading, can impact humans due to induced economic or social disruptions (e.g. slope, bridge and building foundation failures, flotation of buried structures). In this respect, it results of primary interest to map liquefaction induced evidences soon after an earthquake. On the 29th December 2020, a major earthquake (Mw 6.4) occurred in Croatia, close to Petrinja, 45 km south of Zagreb, generating widespread liquefaction and lateral spreading phenomena in a radius of approximately 20 km from the epicentre. A European team of researchers (geologists and engineers), in strict collaboration with the Croatian Geological Survey, performed field reconnaissance campaigns with the aim to provide a detailed identification and characterization of the primary and secondary geological and geotechnical coseismic effects induced by the Croatian earthquakes. Specifically with reference to the liquefaction phenomena, the Working Group integrated the data collected directly in the field with those from remote survey by drone aerial photos acquired in the post-event immediate. The adopted process allowed the collection of the liquefaction record with the highest possible completeness both in terms of pattern and distribution of the phenomena. The database includes several detailed case studies typified by the following characteristics: (1) liquefaction occurring on alluvial plain sites (Kupa river, Sava river and Glina river); (2) blows made by sand and/or gravel with local presence of shells and armored mud balls; (3) lateral spreading phenomena along road and river embankments; (4) sand ejecta of different grain size and matrix, even at the same site; (5) sand and/or gravel ejecta along fault traces. The characteristics of these features are discussed with reference to the alluvial setting and tectonic context. All together, the detailed survey of these recent liquefaction features will assist to build new empirical relations, to update the existing ones and to mitigate the effects of future earthquakes recognizing liquefaction prone areas for a correct land use planning, as for seismic microzonation studies.</p>

Antimony-Gold mineralization in Rates (Northern Portugal)

<p>In the Dúrico-Beirão mining district several paragenetic associations have been described in gold mineralizations, including Sb-Au. The objective of this research was the study of the Sb-Au mineralization in the Rates area, from field reconnaissance of the mineralized structures by soil sampling to the petrographic and mineralogical study of the parageneses associated with this gold mineralization, mined by the Romans.</p><p>The portable XRF was used to measure Sb and As in farms and forest soils. The observed Au-Sb-As anomalies in the Rates area must be linked to Lagoa Negra mine by the same north-western trend fault. Historical mining works have been identified both in Lagoa Negra and in Rates, where rock-chip sampling returned results up to 30 g/t Au from the Rates prospect.</p><p>Some rock samples from Rates were studied by geochemical and petrographic analyses and were analysed in detail by scanning electron microscopy. The results indicate that the paragenetic association in Rates is Sb-Au, with stibnite as primary Sb sulfide mineral, valentinite as alteration mineral, and gold in native and granular form.</p><p><strong>Acknowledgment</strong></p><p>The work was financial supported within the compass of the ERA-MIN/0005/2018—AUREOLE project, FEDER through operation POCI-01-0145-FEDER-007690 funded by the Programa Operacional Competitividade Internacionalização—COMPETE2020 and by National Funds through FCT within the ICT (reference UIDB/04683/2020).</p>

Zagospodarowanie powiatu sokólskiego dla turystyki rowerowej

The purpose of the article is to propose changes in the development of the Sokółka district for bicycle tourism based on data obtained at the beginning of 2020. A field reconnaissance was carried out, and the materials collected and information found on the poviat’s websites were analyzed. A SWOT analysis was prepared in terms of bicycle tourism and, as part of the work, several maps were created through the QGIS program showing both tourist attractions in the Sokółka district and bicycle routes. On the basis of the information obtained, several changes were proposed in order to create places of interest for bicycle tourists in the studied area. A map of potential stopping points for cyclists was also produced and several ideas were proposed to improve the promotion of the area.