M c seems correlated with b -values, so in order to check for a possible interdependency, we performed the same analysis after fixing M c to its highest value of 1. Frequency—magnitude plots in panel a and the relative b -values panel b calculated for each phase of the seismic sequence; texts report the M c s jointly inverted with the b -values. Seismicity rate calculated for each phase is plotted in panel c. Colours and symbols are the same as in Fig. Errors for the b -values and M c s is one bootstrap standard deviation.
Horizontal lines in panels b and c indicate the time period in which the quantities are calculated, markers are placed in the middle point of the time window. Therefore, the increase in the average size of events i. In general, a Poissonian model fits seismicity well only when main shocks are considered, while aftershocks or swarm-like sequences introduce clustering in the earthquake sequences. By means of the coefficient of variation CV , that is the ratio between the standard deviation and mean of the population of interevent times, we check when interevent times depart from an exponential distribution.
As expected, we find a high degree of clustering when we use all data in the sequence Fig. In detail, CV is close to one before the onset of the swarm i. For all the other phases, CV takes values larger than 1, with empirical distribution of interevent time compatible with a power-law model see Fig. This explanation may apply also to the Pollino sequence. Probability density for interevent times IETs of each phase of the sequence.
Colours and symbols are for the phases 0—6 in Fig. Dot-dashed line are IETs for all data. Coefficient of variation CV are reported together with the number of data above the catalogue completeness. In the inset same as the main plot but IETs of each sequence are normalized by their mean values.
Earthquakes swarms are usually the result of the interplay between aseismic forcing acting on tectonically loaded structures and earthquake—earthquake self-interaction. In this way, the observed seismicity results from the contribution of two processes: One is related to stress changes related to aseismic processes, the other one is related to earthquake-induced stress changes.
While the second one is interesting for studying earthquake interactions, the first process is of major interest for exploring the initiation mechanism of the whole sequence. The smoothing window is crucial: For weak smoothing, the model favours a strong time dependence with a large fraction of the earthquakes associated with it, while the time dependence becomes negligible for strong smoothing. We deliberately increase the cut-off magnitude for this analysis since both the inversion and optimization of ETAS parameters are more sensitive to catalogue incompleteness than the statistical analyses previously performed.
The latter model is clearly superior based on its AIC value and indicates that a large number of events were directly driven by an aseismic forcing. The estimated ETAS parameters are all in the range of typical values observed in other regions e. The optimized fit is shown in Fig. After a small increase of the seismicity rate at the beginning of the swarm in October , the first considerable acceleration coincides with phase 3 of the sequence almost one year before the main shock in Fall An even faster acceleration on the transient forcing occurred in the three months before the main shock.
The mapped normal faults in the region are the Mercure Basin fault in the northern part of the Pollino chain, the Pollino fault running WNW—ESE parallel to the mountain chain, and two smaller structures branching off the Pollino fault: Seismicity and tectonics , Statistical seismology , Dynamics: B Detached third leaves of 2. A survey of 71 earthquake bursts across southern California: Role of four calcium transport proteins, encoded by nca-1 , nca-2 , nca-3 , and cax , in maintaining intracellular calcium levels in Neurospora crassa.
Cumulative plot of seismicity versus time. Red curve are observed earthquakes, blue curve indicates the number of events predicted by ETAS model with time dependent background rate and grey shaded curve are expected events related to the transient background rate. One of the major advantages of long lasting seismic sequences is that they allow us to image in detail the hosting tectonic structures. Here, we confirm a possible heterogeneity in the stress field resulting in a more complex transtensional regime with a large component of extension.
Two alternatives are conceivable at this stage for the tectonic structure s activated by the swarm: In case the first scenario applies, this would point at interesting properties of the activated fault. On the other hand, a system of normal faults, as in scenario 2, was mapped in the northern part of the Mercure basin and was activated by the main shock-aftershocks sequence of the September M w 5. In particular, our ETAS-based modelling of the seismicity shows that a large proportion of the events, about 75 per cent, are not aftershocks.
For some swarm sequences it was possible to observe deformation not justified by the energy released seismically. A large role played by fluids either due to increase of pore pressure or fluid infiltration within the seismogenic zone may favour aseismic slip by lowering the normal stress on the fault plane.
Interestingly, the fastest acceleration in the seismic rate occurred in the three months before the largest event in October This was accompanied by a decrease of the b -value, leading to a predicted increased likelihood of a larger magnitude earthquake. In the present case, a high seismicity rate coupled with a low b -value may indicate a change in the dynamics of the aseismic forcing for example a transient decrease of pore pressure or, alternatively, the activation of regions with different rock rheology and thus different seismogenic characteristics. The relation between maximum observed magnitude, b -values and seismic rate should be better investigated in future analyses of seismic swarms.
At the time of the discovery of palaeoseismicity on the Castrovillari fault the lack of large historical earthquakes was explained with a lack of historical data. The faults may therefore now be loaded with large strain.
Episodes of transient slip, releasing the majority of the moment are accompanied by seismic swarms, that release only a small fraction of the energy through seismic waves. High resolution geodetic monitoring can indicate which one of the two scenarios is the most likely by simply budgeting the total geodetic moment accumulated and that released seismically by the sequence. A large aseismic release of geodetic moment during the seismic swarm in the Mercure Basin fault is not inconsistent with the low seismic activity on the Castrovillari fault.
At present, without precise locations and no constraints from deformation data, it is difficult to say if the swarm was accompanied by a large aseismic release of geodetic moment and if the low-seismicity fault portions are linked to creeping or to increased locking. Traditional hazard estimation methods are based on the knowledge of the structures involved and on estimates of the parameters of the Gutenberg—Richter relation, maximum magnitude and ground motion prediction.
Regardless of the physical mechanism in place, during seismic swarms and certainly during the Pollino sequence all these quantities are poorly known or strongly time-dependent and in general affected by large uncertainties. This makes it difficult to estimate the seismic hazard with traditional methods. A possible strategy to decrease uncertainties is to develop methods to incorporate, beside the seismicity and tectonic loading of the area, the monitoring of a large number of parameters: Deformation, changes of velocity of seismic wave in the crust, physico-chemical properties of fluids in wells and thermal- and hot-springs.
Understanding co-variation of those signals with the seismic rate is of crucial importance to better estimate the hazard due to natural and man-made fluid-related seismic activity. In this work, we have examined the geometrical, mechanical and statistical characteristics of the seismic swarm striking the Pollino range region.
We interpret this as a result of the transtensional stress field acting in the southern part of the Mercure Basin. Due to a lack of resolution on the hypocentres of the events, we cannot definitively discriminate the tectonic structures hosting the sequence but we discuss two possible alternative scenarios: One single curved structure or a system of subparallel faults. It is difficult to explain the spatial and temporal evolution of the sequence only in terms of static stress transfer due to the larger earthquakes within the sequence, so we argue for an external forcing as a driving mechanism of the swarm.
The external forcing is confirmed by analysis of the sequence using the ETAS model. Results indicate 75 per cent of the earthquakes in the sequence may be attributed to a transient forcing and the rest is normal aftershock activity. Changes of b -values in time throughout the sequence also support the external forcing hypothesis since low b -values correlate with the period of highest seismicity rate and with the occurrence of the largest shock.
Yet, whether the external forcing is due to transient and aseismic slip episodes can only be resolved by linking high precision earthquake locations and high resolution geodetic monitoring. The comments of Rodolfo Console, an anonymous reviewer and the associate editor Egill Hauksson helped improve the manuscript. The authors thank Marybeth Rice for revising the English.
Oxford University Press is a department of the University of Oxford. It furthers the University's objective of excellence in research, scholarship, and education by publishing worldwide. Sign In or Create an Account. Close mobile search navigation Article navigation. Aseismic transient driving the swarm-like seismic sequence in the Pollino range, Southern Italy Luigi Passarelli.
Abstract Tectonic earthquake swarms challenge our understanding of earthquake processes since it is difficult to link observations to the underlying physical mechanisms and to assess the hazard they pose. Seismicity and tectonics , Statistical seismology , Dynamics: View large Download slide. We model the causative fault as a square dislocation Okada of side 4. The fault strike o , dip 54 o and rake —79 o were set according to the focal mechanism solution in Fig.
A source study of the 9 September M w 5. Analysis of the 9 September M w 5. Materiali per un catalogo dei terremoti italiani: Eventi sconosciuti, rivalutati o riscoperti. Pleistocene strike—slip tectonics in the Lucanian Apennine Southern Italy. Automated procedure for point and kinematic source inversion at regional distances. Discrimination of induced seismicity by full moment tensor inversion and decomposition.
New constraints on the seismic history of the Castrovillari fault in the Pollino gap Calabria, southern Italy. The putative pore loop was inferred from previous analyses [ 18 ]. Multiple sequence alignments of the full-length proteins, including 43 sequences from 20 fungal species, were performed using ClustalW [ 39 ]. Resulting alignments were trimmed with Jalview [ 40 ] S1 File. Subsequent phylogenetic analyses were performed by neighbour joining 10, bootstrap replicates using Phylip hosted at http: A consensus tree was created by using plottree http: Amino acid identity and similarity was calculated with the help of the trimmed alignments that were used for the phylogenetic analysis at http: After the indicated time, leaf discs of 8 mm diameter were excised and immediately frozen in liquid nitrogen.
Four leaf discs were pooled for each point in time. Infection assays were performed in three biological replicates in consecutive weeks. Leaf discs were ground in liquid nitrogen. Calculation of the results was done according to Liu and Saint [ 43 ]. The oligonucleotides used are listed in S1 Table. RNA-Seq data were obtained from the study of Schliebner and co-workers [ 44 ].
To induce the production of falcate conidia, the fungus was grown on oat meal agar OMA [ 45 ]. Colony growth assays were performed as described before [ 45 ]. Colony diameters were recorded daily for 4 to 10 days. Vegetative hyphae of C. For osmotic stress treatments, glycerol was added to mLCM agar prior to autoclaving at the indicated final concentrations. For assays testing growth on different carbon sources, mLCM, potato dextrose agar PDA , and minimal medium supplemented with the respective carbon source were used. PDA was made of 2.
Minimal medium contained salt solutions as used in mLCM, 1. Sodium malate and sodium pectate were obtained by neutralizing DL-malic acid and pectic acid to pH 7. Deletion cassettes were generated by double-joint PCR using the oligonucleotides listed in S1 Table [ 48 ]. Transformation of the C. Transformants were screened by PCR for the presence of the deletion cassette. For this purpose, DNA was isolated by using a quick extraction protocol [ 50 ]. PCR-positive clones were assayed by Southern blotting for homologous integration of the deletion cassette and ectopic integration events.
The probe was generated using the oligonucleotides Hph-5'-South-for and Hph-5'-South-rev S1 Table as described elsewhere [ 49 ]. DNA extraction and blotting were performed as described before [ 51 ]. Cylinders were covered with parafilm and incubated for 30 min in the chamber of the Sirius-1 luminometer. After 1 min baseline recording, 4 mL of a solution pH 7. Aequorin luminescence was recorded for 30 min. Data shown represent three biological repetitions performed on different days.
For subcellular localization and co-localization of the CgTRPF proteins, a dual-tagging plasmid system was employed, following the cloning workflow described by Lange and co-workers [ 50 ]. Oligonucleotides used for the cloning of localization plasmids are listed in S1 Table. Transformation and microscopic analyses were performed as described before [ 50 ]. Germination and appressorium formation were assayed on polystyrene and on onion epidermis.
Segments of the third leaf of day-old maize Zea mays cv. Golden Jubilee plants cultivated in an air-conditioned greenhouse were excised and incubated to assess virulence of C. Comparison with the genomic regions revealed that each of the genes comprises four exons of varying length Fig 1A. The genomic sequences and the gene numbers can be found in S2 File. B Artistic representation forged steel of the TRP channel core structure containing six transmembrane TM domains and a pore loop between TM domain 5 and 6. Cytosolic amino acid residues are indicated in light green, TM domains are shown in yellow, luminal amino acid residues are depicted in light blue, and the predicted pore loop is marked in dark blue.
Acidic amino acid residues [Asp D or Glu E ] are indicated by a red edge, which is boldfaced in motifs of 4 or more consecutive acidic amino acid residues. One circle represents one amino acid residue. The first and the last amino acid of the whole protein, as well as of each TM domain, are enumerated.
There is also a high degree of conservation in the length of the luminal and cytosolic linkers of the TM domains as well as of the putative pore loop S2 Table [ 18 ]. Hence, the C-terminus of those proteins is predicted to reside in the lumen. The obtained sequences were aligned, trimmed, and a phylogenetic tree was generated that comprised six major branches Fig 2. Species belonging to the Saccharomycotina harboured only one putative TRP protein and clustered on a distinct branch. The fifth branch comprises only predicted proteins from Basidiomycota.
In general, all examined filamentous fungi carry one to four predicted TRPF proteins. Colletotrichum higginsianum and Neurospora crassa are the only of the analyzed species containing predicted proteins with similarity to all four CgTRPFs. There is no apparent correlation between nutritional lifestyle or pathogenicity and the number of TRPF proteins per species.
TRPF groups 1, 2, 3, and 4, each containing a C. TRPF group not containing a C. To determine whether the four CgTRPF genes may play a role during growth, we first determined their expression in spores and in colonies cultivated on a membrane overlying mLCM agar, as described by Lange and co-workers [ 41 ]. Full-length transcripts for all four genes were detectable in vegetative hyphae and conidial spores Fig 3A. To determine transcript abundance throughout the infection process on maize, two independent methods were applied on two different cultivars Mikado, Golden Jubilee.
Transcript levels were assessed from 0 to hours post inoculation hpi. Compared to 0 hpi, transcript levels of CgTRPF1 were induced from 12 hpi onward by up to 13 fold in both data sets. Transcript abundances of CgTRPF4 were also consistently elevated throughout earlier stages of the infection process, albeit to a lesser extent Fig 3B and 3C. The transcriptomic data indicate that all four CgTRPF genes may play a role in all stages of growth and infection. B, C Expression during the infection process relative to the expression in spores 0 hours post infection, hpi ; black: CgTRPF1 , dark grey: CgTRPF2 , light grey: B Detached third leaves of 2.
C Third leaf of intact two-week-old drop-infected plants cv. TRP channels of animals localize either at the plasma membrane or at membranes of intracellular organelles, while the S. Because CgTRPF1 through 3 exhibited a similar localization pattern, we investigated whether they are present in the same compartment.
To this end, the respective genes were fused to mCherry and combined with EGFPf fusion constructs in a dual-tag plasmid system [ 50 ]. As all CgTRPF genes were expressed in spores, plate cultures, and throughout the infection process, and since mutants of other fungi for TRPY1 homologues show severe defects [ 37 , 38 ], we analysed the role of CgTRPF1 through 4 in growth and pathogenicity.
To this end, we created deletion strains for each gene by homologous recombination. For further analysis of this gene, three individual strains were chosen that showed different Southern blot patterns for one additional integration event S1 Fig. This may be indicated by an increased expression of the remaining CgTRPF genes in the deletion strains.
In the deletion strains, an occasional weak upregulation of other family members was observed. However, this alteration was always well below two-fold, which does not indicate a strong compensatory response. Therefore, germination was tested on polystyrene Fig 5A and on onion epidermis Fig 5B. In both types of assay, germination of the deletion strains was not reduced compared to the wild type, indicating either no role of the CgTRPF genes in this process or a functional redundancy of the genes.
On onion epidermis, only appressoria were counted. To utilize those, the fungus has to secrete hydrolytic enzymes by exocytosis, allowing the uptake of low-molecular compounds. To test whether CgTRPFs may function in this process or in the utilization of diverse carbon sources, wild type and deletion strains for all of the four genes were assayed for growth on mLCM and PDA, as well as on minimal media supplemented with glucose, sucrose, raffinose, sorbitol, mannitol, malate, pectate, or cellulose.
The strains did not show any consistent and reproducible growth differences on any of the tested media Fig 6. Hence, CgTRPF genes are either not required for those secretion events, or the genes are functionally redundant in this process. All values were normalized to the growth of the wild type on the respective medium. Colony diameter was measured hours post inoculation. This decrease in growth was also apparent, but not exacerbated, in the Cgtrpf mutant strains Fig 7.
As reported previously [ 45 ], the C.
It has been suggested that in N. Kymographs of individual hyphae of wild type and deletion mutants. ROIs of subsequent images, acquired every 2 sec, were plotted one below the other. The slope of the kymographs, read from top to bottom, thus indicates the growth rate.
They were heard on the hydrophones at dawn and the calls included those of L pod. This is their first visit to the Salish Sea this year. The 2 transients porpoised away and continued at high speed to meet the rest of the T60 family plus T2B north of Kelp Reef. Also today was our first sighting of newest L pod member, L, born end of to first time mom, L who became a mom at age L55 with L along Kellett Bluff. L was doing tail lobs continuously throughout the day. L90 Ballena with L92 Crewser heading down island just before he charged at the transient orcas going north in Haro Strait.
This photo was taken moments before the Residents charged in their direction.