Citizen seismology helps decipher the 2021 Haiti earthquake.

On 14 August 2021, the moment magnitude (Mw) 7.2 Nippes earthquake in Haiti occurred within the same fault zone as its devastating 2010 Mw 7.0 predecessor, but struck the country when field access was limited by insecurity and conventional seismometers from the national network were inoperative. A network of citizen seismometers installed in 2019 provided near-field data critical to rapidly understand the mechanism of the mainshock and monitor its aftershock sequence. Their real-time data defined two aftershock clusters that coincide with two areas of coseismic slip derived from inversions of conventional seismological and geodetic data. Machine learning applied to data from the citizen seismometer closest to the mainshock allows us to forecast aftershocks as accurately as with the network-derived catalog. This shows the utility of citizen science contributing to our understanding of a major earthquake.

Triggering of New Madrid seismicity by late-Pleistocene erosion.

The spatiotemporal behaviour of earthquakes within continental plate interiors is different from that at plate boundaries. At plate margins, tectonic motions quickly reload earthquake ruptures, making the location of recent earthquakes and the average time between them consistent with the faults' geological, palaeoseismic and seismic histories. In contrast, what determines the activation of a particular mid-continental fault and controls the duration of its seismic activity remains poorly understood. Here we argue that the concentration of magnitude-7 or larger earthquakes in the New Madrid seismic zone of the central United States since the end of the last ice age results from the recent, climate-controlled, erosional history of the northern Mississippi embayment. We show that the upward flexure of the lithosphere caused by unloading from river incision between 16,000 and 10,000 years ago caused a reduction of normal stresses in the upper crust sufficient to unclamp pre-existing faults close to failure equilibrium. Models indicate that fault segments that have already ruptured are unlikely to fail again soon, but stress changes from sediment unloading and previous earthquakes may eventually be sufficient to bring to failure other nearby segments that have not yet ruptured.

Skin-to-skin contact of fullterm infants: an explorative study of promoting and hindering factors in two Nordic childbirth settings.

AIM: To explore factors that promote or hinder skin-to-skin contact (SSC) during the first days after birth between parents and healthy fullterm infants. METHODS: A total of 117 postnatal mothers and 107 fathers/partners attending two childbirth settings, where Kangaroo mother care (KMC) was implemented as a standard routine of care, one in Sweden and one in Norway, were recruited consecutively and answered questionnaires two weeks postpartum. RESULTS: Satisfaction with support for SSC in postnatal care and being a mother in the Swedish setting was found to promote SSC during the first day postpartum; previous knowledge about SSC increased the practice also during the 2nd and 3rd days. Receiving visitors apart from partner and siblings emerged as a hindering factor. SSC was known of and practised to a larger extent in the Swedish setting, whereas parents in the Norwegian setting received more visitors and were more satisfied with the received information and support for SSC in postnatal care. CONCLUSIONS: The results highlight the need for caregivers to give parents adequate support for practising SSC with their newborn healthy fullterm infants and indicate the importance of developing information routines during the antenatal period as well as in relation to the birth of the child, to effectively introduce and implement SSC.

Seismology: tectonic strain in plate interiors?

It is not fully understood how or why the inner areas of tectonic plates deform, leading to large, although infrequent, earthquakes. Smalley et al. offer a potential breakthrough by suggesting that surface deformation in the central United States accumulates at rates comparable to those across plate boundaries. However, we find no statistically significant deformation in three independent analyses of the data set used by Smalley et al., and conclude therefore that only the upper bounds of magnitude and repeat time for large earthquakes can be inferred at present.

First results of a complete marker-free methodology for human gait analysis.

This paper presents a complete methodology for human gait analysis using a marker-free system. The acquisition system devised is composed of three synchronized and calibrated CCD cameras. The aim of this work is to recognize the leg of a walking human in gray level image sequences, to reconstruct it in the three dimensional space and then to analyze the movements of the body during gait activity. An articulated 3D model of the human body, based on tapered superquadric curves, is first introduced. A motion-based segmentation, using morphological operators is then applied to the image sequences in order to extract the boundaries of the leg in motion. A reconstruction process, based on the use of a Least Median of Squares (LMS) regression is next performed, in order to determine the location of the human body in 3D space. Finally, a spatial coherence is imposed on the reconstructed curves in order to better fit the anatomy of the leg and to take the articulated model into account. Each stage of the proposed methodology was tested both on synthetic images and on real world images of walking humans. After having reconstructed the 3D model of the human, some describing gait parameters were extracted and analyzed in order to detect pathologies or abnormalities.

A 3-D marker-free system for the analysis of movement disabilities--an application to the legs.

The aim of this paper is to describe an approach allowing the analysis of human motion in three-dimensional (3-D) space. The system that we developed is composed of three charge-coupled-device cameras that capture synchronized image sequences of a human body in motion without the use of markers. Characteristic points belonging to the boundaries of the body in motion are first extracted from the initial images. Two-dimensional superquadrics are then adjusted on these points by a fuzzy clustering process. After that, the position of a 3-D model based on a set of articulated superquadrics, each of them describing a part of the human body, is reconstructed. An optical flow process allows the prediction of the position of the model from its position at the previous time, and gives initial values for the fuzzy classification. The results that we present concern more specifically the analysis of movement disabilities of a human leg during gait. They are improved by using articulation-based constraints. The methodology can be used in human motion analysis for clinical applications.