Detailed Investigation of the Foreshock Sequence of the 2010 Mw7.2 El Mayor‐Cucapah Earthquake

Foreshocks can provide valuable information about possible nucleation process of a mainshock. However, their physical mechanisms are still under debate. In this study, we present a comprehensive analysis of the earthquake sequence preceding the 2010 Mw7.2 El Mayor‐Cucapah mainshock, including waveform detection of missing smaller events, relative relocation, and source parameter analysis. Based on a template matching method, we find a tenfold increase in the number of earthquakes than reported in the Southern California Seismic Network catalog. The entire sequence exhibits nearly continuous episodes of foreshocks that can be loosely separated into two active clusters. Relocated foreshocks show several seismicity streaks at depth, with a consistently active cluster at depths between 14 and 16 km where the mainshock was nucleated. Stress drop measurements from a spectral ratio approach based on empirical Green’s functions show a range between 3.8 and 41.7 MPa with a median of 13.0 MPa and no clear temporal variations. The relocation results, together with the source patches estimated from earthquake corner frequencies, revealed a migration front toward the mainshock hypocenter within last 8 hr and a chain of active burst immediately 6 min prior to the mainshock. Our results support combined effects of aseismic slip and cascading failure on the evolution of foreshocks.Plain Language SummaryThe 2010 Mw7.2 El Mayor‐Cucapah (EMC) earthquake was preceded by a prominent sequence of foreshocks starting ~21 days before the mainshock. Several methods based on the similarities of waveforms are applied to obtain spatiotemporal evolution of foreshocks. Ten times more events are found from a template matching method when compared to the SCSN catalog. The refined relative locations reveal two main active clusters in time, as well as two spatial patches with a shallower one to the north of the mainshock epicenter. The depth distribution indicates several linear lines of seismicity, with a consistently active cluster at depths of 14–16 km where mainshock started. An active cluster of foreshocks occurred in the last 6 min. They likely altered the stress state near the hypocenter and ultimately triggered the mainshock. Our analysis indicates that both aseismic slip and cascade triggering processes occurred and contributed to the eventual triggering of the EMC mainshock.Key PointsA waveform matching technique leads to tenfold increase in the number of foreshocks when compared with the SCSN catalogWe resolve the corner frequency of 20 foreshocks using the detected events as empirical Green’s functionsThe relocated catalog and estimated source patches reveal effects of both aseismic slip and cascading stress transferPeer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155988/1/jgrb54188.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/155988/2/jgrb54188_am.pd

Perceptions of Women and Men Leaders Following 360‐Degree Feedback Evaluations

In this study, researchers used a customized 360‐degree method to examine the frequency with which 1,546 men and 721 women leaders perceived themselves and were perceived by colleagues as using 10 relational and 10 task‐oriented leadership behaviors, as addressed in the Management‐Leadership Practices Inventory (MLPI). As hypothesized, men and women leaders, as well as their supervisors, employees, and peers, perceived women leaders to employ nine of the 10 relational leadership behaviors significantly more frequently than men leaders. Additionally, the employees' perceptions of their women leaders' use of task‐oriented behaviors were significantly higher when compared to similar assessments from the employees of men leaders. However, the leaders as well as their supervisors and peers perceived men and women leaders' use of task‐oriented behaviors as approximately equal. Broader implications of these findings are discussed.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97470/1/21134_ftp.pd

Centrosome defects cause microcephaly by activating the 53BP1-USP28-TP53 mitotic surveillance pathway

Mutations in centrosome genes deplete neural progenitor cells (NPCs) during brain development, causing microcephaly. While NPC attrition is linked to TP53-mediated cell death in several microcephaly models, how TP53 is activated remains unclear. In cultured cells, mitotic delays resulting from centrosome loss prevent the growth of unfit daughter cells by activating a pathway involving 53BP1, USP28, and TP53, termed the mitotic surveillance pathway. Whether this pathway is active in the developing brain is unknown. Here, we show that the depletion of centrosome proteins in NPCs prolongs mitosis and increases TP53-mediated apoptosis. Cell death after a delayed mitosis was rescued by inactivation of the mitotic surveillance pathway. Moreover, 53BP1 or USP28 deletion restored NPC proliferation and brain size without correcting the upstream centrosome defects or extended mitosis. By contrast, microcephaly caused by the loss of the non-centrosomal protein SMC5 is also TP53-dependent but is not rescued by loss of 53BP1 or USP28. Thus, we propose that mutations in centrosome genes cause microcephaly by delaying mitosis and pathologically activating the mitotic surveillance pathway in the developing brain

Phylogeography of an endangered disjunct herb: long-distance dispersal, refugia and colonization routes

Quaternary glacial cycles appear to have had a consistent role in shaping the genetic diversity and structure of plant species. Despite the unusual combination of the characteristics of the western Mediterranean– Macaronesian area, there are no studies that have specifically examined the effects of palaeoclimatic and palaeogeographic factors on the genetic composition and structure of annual herbs. Astragalus edulis is a disjunct endemic found in the easternmost Canary Islands and the semi-arid areas of north-eastern Africa and south-eastern Iberian Peninsula. This endangered species shows no evident adaptations to long-distance dispersal. Amplified fragment length polymorphism (AFLP) data and plastid DNA sequences were analysed from a total of 360 individuals distributed throughout the range of this species. The modelled potential distribution of A. edulis under current conditions was projected over the climatic conditions of the Last Interglacial (130 ka BP) and Last Glacial Maximum (21 ka BP) to analyse changes in habitat suitability and to look for associations between the modelling and genetic results. Amplified fragment length polymorphism analysis showed clear phylogeographic structure with four distinct genetic clusters. Approximate Bayesian computation (ABC) models based on plastid DNA sequences indicated a Middle Pleistocene long-distance dispersal event as the origin of the populations of the Canary Islands. The models also suggested south-western Morocco as the ancestral area for the species, as well as subsequent colonization of north-eastern Morocco and the Iberian Peninsula. The data compiled indicated the possibility of the presence of refuge areas at favourable locations around the High Atlas and Anti-Atlas mountain ranges. Moreover, palaeodistribution models strongly support the events inferred by ABC modelling and show the potential distribution of the species in the past, suggesting a putative colonization route.This work has been financed by the Spanish Ministerio de Ciencia e Innovación through the projects CGL2012- 32574 and REN2003-09427, as well as by the Andalusian Consejería de Innovación, Ciencia y Tecnología through the project RNM1067. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript

Consistent phenological shifts in the making of a biodiversity hotspot: the Cape flora

Background The best documented survival responses of organisms to past climate change on short (glacial-interglacial) timescales are distributional shifts. Despite ample evidence on such timescales for local adaptations of populations at specific sites, the long-term impacts of such changes on evolutionary significant units in response to past climatic change have been little documented. Here we use phylogenies to reconstruct changes in distribution and flowering ecology of the Cape flora - South Africa's biodiversity hotspot - through a period of past (Neogene and Quaternary) changes in the seasonality of rainfall over a timescale of several million years. Results Forty-three distributional and phenological shifts consistent with past climatic change occur across the flora, and a comparable number of clades underwent adaptive changes in their flowering phenology (9 clades; half of the clades investigated) as underwent distributional shifts (12 clades; two thirds of the clades investigated). Of extant Cape angiosperm species, 14-41% have been contributed by lineages that show distributional shifts consistent with past climate change, yet a similar proportion (14-55%) arose from lineages that shifted flowering phenology. Conclusions Adaptive changes in ecology at the scale we uncover in the Cape and consistent with past climatic change have not been documented for other floras. Shifts in climate tolerance appear to have been more important in this flora than is currently appreciated, and lineages that underwent such shifts went on to contribute a high proportion of the flora's extant species diversity. That shifts in phenology, on an evolutionary timescale and on such a scale, have not yet been detected for other floras is likely a result of the method used; shifts in flowering phenology cannot be detected in the fossil record

Extinction Risk and Diversification Are Linked in a Plant Biodiversity Hotspot

Plant extinction risks in the Cape, South Africa differ from those for vertebrates worldwide, with young and fast-evolving plant lineages marching towards extinction at the fastest rate, but independently of human effects