1,720,987 research outputs found
Landslides triggered by multiple earthquakes: insights from the 2018 Lombok (Indonesia) events
No full textEarthquake-triggered landslides significantly contribute to worsening the impact of seismic events; thus, comprehensive landslide inventories are essential for improving seismic hazard assessment. During complex seismic sequences, landslides are triggered by more than one event and the final inventory reflects the spatial and temporal evolution of the sequence. Here, I analyze the landslides triggered by the 2018 Lombok (Indonesia) seismic sequence. I use high-resolution satellite imagery to map 4823 landslides triggered after the 05/08/2018 event (Mw 6.9) and 9319 landslides after the 19/08/2018 event (Mw 6.9). I analyze the distribution and evolution over time of landslide density and landslide area percentage. Despite the significant increase in number and cumulative area of the landslides, the 05/08 and 19/08 events share the maximum dimension of individual landslides; this suggests that the maximum intensity is equal for the two events, i.e., X on the Environmental Scale Intensity scale. I compare the distribution of landslides with macroseismic information provided by eyewitnesses through online questionnaires. Finally, I investigate the role of earthquake environmental effects within seismic sequences, showing that effects on the natural environment provide complementary information with respect to traditional intensity and felt reports
Conditional probability of distributed surface rupturing during normal-faulting earthquakes
Full text linkCoseismic surface faulting is a significant source of hazard for critical plants and distributive infrastructure; it may occur either on the principal fault or as distributed rupture on nearby faults. Hazard assessment for distributed faulting is based on empirical relations which, in the case of normal faults, were derived almost 15 years ago using a dataset of US earthquakes. We collected additional case histories worldwide, for a total of 21 earthquakes, and calculated the conditional probability of distributed faulting as a function of distance from the principal fault. We found no clear dependency on the magnitude nor the time of occurrence of the earthquakes, but our data consistently show a higher probability of rupture when compared with the scaling relations currently adopted in engineering practice. We derive updated empirical regressions and show that the results are strongly conditioned by the averaging of earthquakes effectively generating distributed faulting at a given distance and those which did not generate faulting; thus, we introduce a more conservative scenario that can be included in a logic tree approach to consider the full spectrum of potential ruptures. Our results can be applied in the framework of probabilistic assessment of fault displacement hazard
Earthquake-triggered landslides and Environmental Seismic Intensity: insights from the 2018 Papua New Guinea earthquake (Mw 7.5)
Full text linkOn the 25 February 2018, an earthquake of magnitude M(w)7.5 struck the region of Porgera in Papua New Guinea (PNG), triggering numerous landslides. Planetscope images are used to derive a partial inventory of 2941 landslides in a cloud-free area of 2686 km(2). The average area of landslides in the study area is 18,500 m(2). We use the Environmental Seismic Intensity (ESI) scale to assess the damage due to the triggered landslides. Local intensity values are assigned to individual landslides by calculating their volume using various area-volume relations. We observe that different empirical relations yield similar volume values for individual landslides (local ESI intensity & GE; X). The spatial variation of landslide density and areal coverage within the study area in cells of 1 km(2) is investigated and compared to the probability predicted by the USGS model. We observe that high probability corresponds to a significant number of landslides. An ESI epicentral intensity of XI is estimated based on primary and secondary effects. This study represents the first application of the ESI scale to an earthquake in PNG. The Porgera earthquake fits well with past case studies worldwide in terms of ESI scale epicentral intensity and triggered landslide number as a function of earthquake magnitude
Characterizing the Distributed Faulting During the 30 October 2016, Central Italy Earthquake: A Reference for Fault Displacement Hazard Assessment
Full text linkModerate to strong earthquakes (i.e., Mw > ~6.0) commonly produce a complex network of ground ruptures, which are responsible for significant damage. Distributed faulting can affect wide areas (tenths of square kilometers), and expected displacement can be estimated through a probabilistic approach, considering distance from the primary fault and earthquake magnitude. Other factors may have a role in driving the occurrence of distributed faulting; nevertheless, they are not adequately addressed in the current modeling, due to a sensible lack of information. We study the 30 October 2016, Central Italy earthquake (Mw 6.5), to analyze the spatial pattern and geometric characteristics of distributed faulting. We found that distance from the primary structure, fault geometry, and lithology are key factors controlling the distributed faulting occurrence; the local structural setting (i.e., synthetic versus antithetic normal faults systems and relay zones) drives the spatial distribution of faults and the partitioning of the deformation. We also examine other four events occurred in the Italian Apennines since 1980, confirming that traditional models can underestimate the probability of distributed faulting. We suggest that a purely distance-based probabilistic approach should be integrated using additional parameters derived from earthquake deformation fields or considering the reactivation of preexisting faults
Detection of landslide timing, reactivation and precursory motion during the 2018, Lombok, Indonesia earthquake sequence with Sentinel-1
No full textEarthquake-triggered landslides can be mapped using optical satellite images, but assessing how they evolve during earthquake sequences is difficult due to cloud cover in these data. This information is crucial for understanding their triggering conditions. Here we use Sentinel-1 amplitude and a new, coherence-based method to characterise the evolution of rapid landslides during an earthquake sequence that occurred over a 23 d period in 2018 in Lombok, Indonesia. While most new landslides were triggered during the largest earthquake in the sequence on 5 August, we also identified landslide activity associated with other, lower magnitude earthquakes on 28 July, 9 and 19 August, with around half of the landslides studied active in more than one earthquake. In particular, many landslides triggered by the 5 August earthquake were then reactivated later in the sequence. These reactivations were triggered by accelerations as weak as 0.1 g, while new failures generally did not occur below 0.15 g, suggesting a post-seismic weakening effect driven by the landslides themselves rather than general landscape weakening. We also identified an example where possible precursory motion detected during the first earthquake in the sequence was later followed by larger scale failure. Overall, we demonstrate that, although they are not sensitive to all landslides and are more likely to detect larger events, Sentinel-1 amplitude and coherence are valuable tools to study how landslide hazard and mass wasting evolve during sequences of triggers
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
The Mid-eighth Century CE Surface Faulting Along the Dead Sea Fault at Tiberias (Sea of Galilee, Israel)
No full textThe Dead Sea Fault (DSF) is a plate-boundary where large earthquakes are expected, but there is a lack of such events in the instrumental era. Sequences of earthquakes along the DSF are documented by historical evidence, one of the most devastating occurred in the mid-eighth century CE. Here we describe site-specific archaeoseismological observations at the ancient Tiberias city, on the western shore of the Sea of Galilee. We map Roman and Byzantine relics faulted in the mid-eighth century CE by a pure normal fault. We use geophysical, geomorphological, and structural analyses integrated with published data, to assess the seismic hazard of the Jordan Valley Western Boundary Fault (JVWB). We propose that the normal JVWB can rupture the surface along its ~45 km trace running from Tiberias toward the S crossing Bet Shean, Tel Rehov, and Tel Teomim. The JVWB, parallel to the main strike-slip Jordan Valley Fault segment, might be regarded as a major earthquake source in this region. We test the hypotheses of both single fault and multifaults rupture scenarios, which result in an expected range of Mw from 6.9 (single rupture of the JVWB) to 7.6 (multiple rupture of the JVWB and Jordan Valley Fault). Our results suggest that seismic source characterization in the Sea of Galilee region must include normal faults capable of surface rupturing, despite the absence of such events in the instrumental catalogue
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