an integrated study of anomalies observed before four major earthquakes 2004 sumatra m9 3 2006 pingtung m7 0 2007 chuetsu oki m6 8 and 2008 wenchuan m8 0 abstract in this paper we cross examine anomalies before four major earthquakes sumatra indonesia 2004 12 26 m9 3 pingtung taiwan 2006 12 26 m7 0 2 chuetsu oki japan 2007 7 16 m6 8 and wenchuan china 2008 5 12 m8 0 measurements of the crustal stress infrasonic wave and budgerigar jumping rate recorded at institute of earthquake prediction are used to monitor in the lithosphere and atmosphere while the total electron content over the four epicenters are employed to detect anomalies in the ionosphere these cross examinations allow us to have better understanding on the leading time of the four observed anomalies the earthquake preparation process and the lithosphere atmosphere ionosphere coupling before the earthquakes

further investigations of geomagnetic diurnal variations associated with the 2011 off the pacific coast of tohoku earthquake mw 9 0 abstract as one of the most promising candidates for short term earthquake forecasting the seismo electromagnetic phenomena have been intensively studied for several decades recently xu et al 2013 have reported unusual behaviors of geomagnetic diurnal variations in the vertical component prior to the 2011 off the pacific coast of tohoku earthquake mw 9 0 to validate this result further investigations have been applied in this study geomagnetic data of 16 years long term observation have been analyzed using the same method in xu et al 2013 ratios of diurnal variation range between the target station esashi esa which is about 130 km from the epicenter and the remote reference station kakioka kak about 300 km distant to the epicenter have been computed after removing seasonal variations revealed by wavelet transform analysis the 15 day mean values of the ratios in the vertical component shows a clear anomaly exceeding the statistical threshold about 2 months before the mega event this anomaly is unique over a 16 year long background and further discussions indicate that this anomaly is unlikely caused by strong geomagnetic storms or a statistical fluke therefore this study has provided a strong support to the previous results in xu et al 2013

provenance constraints from detrital zircon u pb ages in the nw iberian massif implications for palaeozoic plate configuration and variscan evolution detrital zircons from pre orogenic upper ordovician to devonian low grade metasedimentary rocks have been dated by laser ablation inductively coupled plasma mass spectrometry la icp ms to 1 constrain the variations of zircon age populations within the autochthonous sequences of nw iberia 2 compare u pb detrital zircon ages with previous data 3 test the hypothesis of the armorica microplate as a peri gondwanan terrane separated from gondwana the similarity in the ages of detrital zircons found in the palaeozoic samples studied here to those published for the upper proterozoic lower cambrian and lower ordovician sediments of nw iberia argues against the separation of armorica and points to a common source area for all of the palaeozoic detrital formations of nw iberia the west african craton and the surrounding pan african belts la icp ms u pb dating of zircons from a synorogenic flysch preserved in klippen in the core of a syncline establishes a maximum depositional age for this deposit as early namurian this age is also a maximum age limit for thrusting and refolding in this part of the iberian massif correlation of the zircon age populations with published ages confirms the link between the emplacement of the allochthonous complexes of nw iberia and synorogenic sedimentation

ophiolite obduction pulses as a proxy indicator of superplume events abstract a major new synthesis of ophiolite geochronology and map of global phanerozoic distribution indicates that previously noted pulses of ophiolite obduction can be linked to superplume related tectonism a marked cyclicity is evident in obduction ages obtained from minerals in ophiolite metamorphic soles and obduction related minor intrusions this episodicity is in phase with periods of predominantly uniform polarity of the geomagnetic field formation of massive carbon rich deposits sea level highstands and formation of large flood basalt provinces all generally considered to be superplume proxy indicators a key to interpreting ophiolite obduction as a further proxy is the mid cretaceous superplume associated ocean margin compressional deformation during this event thermal rejuvenation and increased buoyancy of ocean lithosphere caused arc terrane collision marginal basin shoaling back arc basin closure and ophiolite obduction convergent margins were placed in compression with increased coupling between subducting and overriding plates resulting in major ocean margin deformation being directly datable and tectonically and petrologically distinctive makes ophiolite assemblages of considerable use for identifying superplume events

a statistical analysis of ionospheric anomalies before 736 m6 0 earthquakes during 2002 2010 1 this paper presents a statistical study of the pre earthquake ionospheric anomaly by using the total electron content tec data from the global ionosphere map a total of 736 m 6 0 earthquakes in the global area during 2002 2010 are selected the anomaly day is first defined then the occurrence rates of abnormal days for both the days within 1 21 days prior to the earthquakes pe and the background days pn are calculated the results show that the values of pe depend on the earthquake magnitude the earthquake source depth and the number of days prior to the earthquake the pe is larger for earthquakes with greater magnitude and lower depth and for days closer to the earthquakes the results also show that the occurrence rate of anomaly within several days before the earthquakes is overall larger than that during the background days especially for the large magnitude and low depth earthquakes these results indicate that the anomalous behavior of tec within just a few days before the earthquakes is related with the forthcoming earthquakes with high probability

a statistical study of ionospheric earthquake precursors monitored by using equatorial ionization anomaly of gps tec in taiwan during 2001 2007 abstract in this paper we examine pre earthquake ionospheric anomalies by the total electron content tec derived from a ground based receiver of the global positioning system gps a network of eight gps receivers is used to construct daily latitude time tec ltt plots to monitor the crest of equatorial ionization anomaly eia in the taiwan area three parameters of the strength location and formation time of the eia crest are extracted a 15 day running medians of the three parameters and the associated upper and lower quartiles are utilized as the references for identifying abnormal signals for all of the 150 m 5 0 earthquakes in the taiwan area during 2001 2007 results show that the eia crest significantly moves equatorward poleward and appears in an earlier later time of the afternoon period a few days before after the earthquakes along the taiwan longitude the two parameters of the eia crest location and occurrence time can be employed to detect ionospheric earthquake precursors the results further imply that atmospheric electric fields generated around the epicenter of a forthcoming earthquake during the preparation period are essential

high pressure micro inclusions and development of an inverted metamorphic gradient in the santiago schists ordenes complex nw iberian massif spain evidence of subduction and syncollisional decompression the santiago schists are located in the basal unit of the ordenes complex one of the allochthonous complexes outcropping in the inner part of the hercynian belt in the north west of the iberian peninsula their tectonothermal evolution is characterized by the development of an eo hercynian metamorphic episode c 374 ma of high p low to intermediate t the mineral assemblage of the high p episode is preserved as a very thin si s1 foliation included in albite porphyroblasts being composed of albite garnet i white mica 1 chlorite 1 epidote quartz rutile ilmenite the equilibrium conditions for this mineral assemblage have been estimated by means of different thermobarometers at 495 10 c and 14 7 0 7 kbar probably minimum pressure the later evolution syn d2 of the schists defines a decompressive and slightly prograde p t path which reached its thermal peak at c 525 10 c and 7 kbar decompression of the unit occurred contemporaneously with an inversion of the metamorphic gradient so that the zones of garnet ii biotite with an upper subzone with chloritoid and staurolite developed from bottom to top of the formation the estimated p t path for the santiago schists suggests that the basal unit probably a fragment of the gondwana continental margin was uplifted immediately after its subduction at the beginning of the hercynian orogeny it also suggests that the greater part of the unroofing history of the unit took place in a context of ductile extension probably related to the continued subduction of the gondwana continental margin and the contemporaneous development of compensatory extension above it the inverted metamorphic gradient seems related to conductive heat transferred from a zone of the mantle wedge above the subducted continental margin when it came into contact with the upper parts of the schists along a detachment probably of extensional character the general metamorphic evolution of the santiago schists with the development of high p assemblages with garnet prior to decompressive and prograde parageneses with biotite is unusual in the context of the european hercynian belt and shows a close similarity to the tectonothermal evolution of several high p low to intermediate t circum pacific belts

pre earthquake signals underlying physical processes abstract prior to large earthquakes the earth sends out transient signals sometimes strong more often subtle and fleeting these signals may consist of local magnetic field variations electromagnetic emissions over a wide range of frequencies a variety of atmospheric and ionospheric phenomena great uncertainty exists as to the nature of the processes that could produce such signals both inside the earth s crust and at the surface the absence of a comprehensive physical mechanism has led to a patchwork of explanations which are not internally consistent the recognition that most crustal rocks contain dormant electronic charge carriers in the form of peroxy defects o 3 si oo sio 3 holds the key to a deeper understanding of these pre earthquake signals from a solid state physics perspective when rocks are stressed peroxy links break releasing electronic charge carriers h known as positive holes the positive holes are highly mobile and can flow out of the stressed subvolume the situation is similar to that in a battery the h outflow is possible when the battery circuit closes the h outflow constitutes an electric current which generates magnetic field variations and low frequency em emissions when the positive holes arrive at the earth s surface they lead to ionization of air at the ground air interface under certain conditions corona discharges occur which cause rf emission the upward expansion of ionized air may be the reason for perturbations in the ionosphere recombination of h charge carriers at the surface leads to a spectroscopically distinct non thermal ir emission

potential earthquake precursory pattern from space the 2015 nepal event as seen by magnetic swarm satellites abstract a large earthquake of 7 8 magnitude occurred on 25 april 2015 06 26 utc with the epicenter in nepal here taking advantage of measurements provided by the swarm magnetic satellites we investigate the possibility to detect some series of pre earthquake magnetic anomalous signals likely due to a lithosphere atmosphere ionosphere coupling that can be a potential earthquake precursory pattern different techniques have been applied to swarm data available during two months around earthquake occurrence from the detected magnetic anomalies series during night and magnetically quiet times or with an automatic detection algorithm we show that the cumulative number of anomalies follows the same typical power law behavior of a critical system approaching its critical time and hence recovers as the typical recovery phase after a large event the similarity of this behavior with the one obtained from seismic data analysis and the application of the analyses also to another period without significant seismicity do support a lithospheric linked origin of the observed magnetic anomalies we suggest that they might be connected to the preparation phase of the nepal earthquake

temporal and spatial precursors in ionospheric total electron content of the 16 october 1999 mw7 1 hector mine earthquake 1 in this paper temporal and spatial analyses are employed to detect seismo ionospheric precursors sips in the ionospheric total electron content tec during the 16 october 1999 mw7 1 hector mine earthquake to discriminate anomalies caused by global effects such as solar radiations magnetic storms etc and local effects such as earthquake we cross examine the gps tecs and their gradients in the eastward and northward directions at epicenter centers of the hector mine area and the other two reference areas at similar magnetic latitudes in europe and japan temporal variations of the northward tec gradient suggest sips most likely appearing on days 6 5 before the earthquake a global search by using the tec of the global ionosphere map shows that the tec increase and decrease anomalies continuously and specifically appear around the epicenter on day 5 before the earthquake

structure of the xigaze ophiolite yarlung zangbo suture zone southern tibet china genetic implications three massifs in the xigaze area southern tibet china have been preserved from the intense deformation observed everywhere else in the yarlung zangbo suture zone these massifs have similar lithologies and display a remarkable homogeneity in the attitude of most magmatic and tectonic structures such as lava flow planes dolerite dikes and sills and foliation planes in peridotites this indicates that these ophiolites are only slightly dismembered inasmuch as they locally display complete sequences from pillow lavas at the top to fresh cr diopside bearing harzburgites at the base gabbroic rocks are rare and are present as screens between dolerite intrusives or in small sized pockets at the limit between mafic and ultramafic rocks one of the most important feature of this ophiolite is the occurrence of dolerite sills and dikes throughout the whole sequence indicating that this ophiolite results from to two successive magmatic events with 1 creation of the crustal part of the oceanic lithosphere with deposition of minor cumulates in small magma chambers over mantle residual rocks and 2 intrusion of dolerite sills and dikes throughout the whole sequence

the galicia ossa morena zone proposal for a new zone of the iberian massif variscan implications abstract correlation of a group of allochthonous terranes referred to as basal ophiolitic and upper units exposed in the nw and sw of the iberian massif is used to propose a new geotectonic zone in the southern branch of the variscan orogen the galicia ossa morena zone recent advances in sw iberia identify most of the former ossa morena zone as another allochthonous complex of the iberian massif the ossa morena complex equivalent to the cabo ortegal ordenes malpica tui braganca and morais complexes described in nw iberia the new geotectonic zone and its counterparts along the rest of the variscan orogen constitute an internal variscan zone with ophiolites and units affected by high p metamorphism the galicia ossa morena zone includes a variscan suture and pieces of continental crust bearing the imprint of ediacaran cambrian events related to the activity of peri gondwanan magmatic arcs cadomian orogenesis in the iberian massif the general structure of this geotectonic zone represents a duplication of the gondwanan platform the outboard sections being juxtaposed on top of domains located closer to the mainland before amalgamation this interpretation offers an explanation that overcomes some issues regarding the differences between the stratigraphic and paleontological record of the central and southern sections of the iberian massif also equivalent structural relationships between other major geotectonic domains of the rest of the variscan orogen are consistent with our interpretation and allow suspecting similar configurations along strike of the orogen a number of issues may be put forward in this respect that potentially open new lines of thinking about the architecture of the variscan orogen

ediacaran palaeozoic tectonic evolution of the ossa morena and central iberian zones sw iberia as revealed by sm nd isotope systematics abstract sm nd isotopic analyses of palaeozoic sedimentary and igneous rocks in the southwest iberian massif western end of the european variscan belt are presented in order to unravel its complex poly orogenic evolution during the closure of the rheic ocean and the amalgamation of pangea the gondwanan margin in southwest iberia sw iberia is subdivided into the ossa morena and central iberian zones separated by the badajoz cordoba shear zone which represents a cryptic suture zone between these terranes the relationships between these terranes and between units preserved within the suture zone e g the sierra albarrana group during the palaeozoic and neoproterozoic are controversial sm nd isotopic studies of representative sedimentary sequences covering the entire pre variscan record of the ossa morena and central iberian zones show very similar characteristics from the uppermost ediacaran onwards these data indicate that their accretion to one another must have been completed by the late neoproterozoic ediacarin that time an event assigned to cadomian orogeny and that they never separated substantially from each other since that time the sm nd isotopic composition of the sierra albarrana group metasedimentary rocks is similar to that of the pre cadomian sequences of the ossa morena zone serie negra suggesting derivation from a common source the common provenance of the palaeozoic sequences in the two zones is identical to that of the pre cadomian serie negra of the ossa morena zone which in accordance with the data presented herein and published u pb zircon data indicates a west african affinity

variscan exhumation of a subducted paleozoic continental margin the basal units of the ordenes complex galicia nw spain a structural and metamorphic study was carried out in the basal units of the ordenes complex in spain thought to represent a subducted part of the paleozoic margin of gondwana according to their metamorphic evolution this part of the margin was subducted at the onset of the variscan orogeny becoming part of an accretionary complex developed below a colliding element built previously variations in the pt conditions of the first high pressure metamorphic event along the units indicate a polarity of the subduction to the west subsequent underthrusting of more continental material blocked the subduction and triggered the ascent and exhumation of the basal units whereas the convergence continued recumbent folds and thrusts developed along with successive normal detachments compressional and extensional structures were synchronous or alternated in time and together induced the thinning and tapering of the orogenic wedge and its lateral spreading the unroofing took place locally under an inverted temperature gradient caused by a detachment which carried a part of the hot mantle wedge above the subduction zone over the subducted units

diachronous variscan tectonothermal activity in the nw iberian massif evidence from 40ar 39ar dating of regional fabrics abstract multigrain concentrates of hornblende and muscovite together with whole rock slate phyllite samples have been dated 27 analyses using 40ar 39ar incremental release methods along a systematic traverse across the various lithotectonic structural elements which comprise northwestern sectors of the variscan iberian massif hornblende concentrates from amphibolites in the allochthonous ordenes complex yield plateau isotope correlation ages of 425 ma and 377 ma muscovite concentrates and whole rock slate phyllite from this and the cabo ortegal complex yield plateau ages which range from 367 ma to 295 ma analyses of similar material from the relative autochthon yield plateau ages between 359 ma and 275 ma muscovite concentrates from three late to post kinematic granitic stocks yield plateau ages between 309 ma and 274 ma at least seven of the 40ar 39ar analyses from metamorphic rocks record variable thermal rejuvenation of intracrystalline argon systems associated with emplacement of proximal granitic stocks the remaining analyses may be used to constrain the local age of various variscan tectonothermal events the oldest fabric ages are recorded in allochthonous units whereas the youngest fabric ages occur along the boundary between internal and external zones middle devonian ages are recorded in the allochthon and suggest a chronological continuity with deformational events in the relative autochthon where variscan deformation initiated in the upper devonian and diachronously prograded eastward the first deformational events recorded in the limit within the internal and external zones occured ca 20 25 ma later lower namurian variscan deformation systematically prograded diachronously eastward across the orogen as new crustal material was added along the front of the developing orogenic wedge however the entire orogen remained tectonically active with different structural features forming at different times and at different places an average propagation rate of ca 5 km m y is suggested by consideration of a 20 25 ma difference in correlative fabric ages and present separations

short term earthquake prediction current status of seismo electromagnetics abstract loss of human lives as a result of earthquakes is caused overwhelmingly by the collapse of buildings within less than a few minutes of main shocks the most urgent countermeasure consists of two key elements one is strengthening of weak structures and the other is short term earthquake prediction short term prediction needs precursors although some promising precursors are reported the prevailing views in japan and elsewhere are overly pessimistic the pessimism largely roots in the fact that short term precursors are generally non seismic and tools developed for seismology are not designed to detect them nonetheless nationally funded large scale earthquake prediction programs always emphasize the need to reinforce seismometer networks they do not take into account the views of those in the science community who point to the importance of non seismic precursors while there are well founded causes to be skeptical the situation needs to be improved one reason for skepticism is that the observations of precursors have not yet been perfect enough and another is that some important fundamental aspects of non seismic precursors are still unresolved we review some of these problems

possible ionosphere and atmosphere precursory analysis related to mw 6 0 earthquakes in japan abstract the attention towards possible link of earthquakes eqs and ionosphere in the form of seismo ionosphere anomalies sias has increased exponentially by utilizing new data and more accurate observations the integrated atmosphere and ionosphere monitoring satellites has played a decisive role in this development and provided detection and analysis of anomalies attributed to seismic processes in this paper we study eq anomalies in ionosphere from igs permanent global navigation satellite systems gnss based total electron content tec and fof2 parameter highest frequency reflected from the main ionospheric f2 layer on a vertical propagation path retrieved from stations operating within the seismogenic zone in japan for eqs of magnitude mw 6 0 furthermore spatial composite maps of geopotential height air temperature and outgoing long wave radiation olr from national oceanic and atmospheric administration national center for environmental prediction noaa ncep are analyzed to support the hypothesis of diffusion of sias through the atmosphere over the epicenter during the seismic preparation zone we find evidences of tec and fof2 anomalies in the analysis of nearby igs permanent stations within seismogenic zone on main shock day when geomagnetic activities remain quiet in addition atmospheric composite indices manifest anomalies attributed to the eq on the same day as tec and fof2 perturbations similarly differential ionosphere and atmosphere values indicate that eq abnormalities are significant on main shock day during ut 10 12 our results show that atmospheric and ionospheric measurements may play a role for the analysis and prediction of eqs

gnss ionospheric seismology recent observation evidences and characteristics abstract the detail and nature of earthquakes are still challenging from traditional technique observations e g seismometers and strong motion accelerographs nowadays the ionospheric total electron content tec can be obtained from ground based global navigation satellite systems gnss and space borne gnss radio occultation which can be used to investigate the seismo ionospheric disturbances and may provide insights on the earthquake in this paper gnss ionospheric seismology is presented and reviewed including methods observation results and characteristics case studies of the 2008 wenchuan earthquake and 2011 japan earthquake are presented using ground based gnss observations significant co post seismic ionospheric anomalies are found from continuous gnss observations near the epicenters showing that the seismic ionospheric total electron content tec disturbances were derived mainly from the main shock the detailed pattern and evolution of the ionospheric disturbance are revealed by denser gnss observations some simulations explore the nature of the ionospheric perturbation highlighting that acoustic gravity waves are generated close to the epicenter and that surface rayleigh waves and tsunamis generate in the atmosphere ionosphere acoustic and gravity waves respectively these waves are induced by solid earth ocean and atmosphere coupling at the ground or ocean interface with the atmosphere propagating upward until the ionosphere create strong perturbation in plasma density and plasma velocity

polyphase variscan emplacement of exotic terranes morais and braganca massifs onto iberian successions evidence from 40ar 39ar mineral ages abstract the braganca and morais nappe complexes comprise internally imbricated continental tectonic units including schists deformed metagranite granulite and local eclogite and a structurally underlying ophiolite nappe high pressure assemblages in some of the continental sequences were variably retrogressed during an amphibolite facies metamorphic overprint by contrast rocks within the ophiolite nappe display prograde amphibolite facies assemblages hornblende concentrates from both tectonic units exposed in the braganca nappe complex record 40 ar 39 ar plateau and isotope correlation ages of c 385 390 ma a similar date is recorded by hornblende within mylonitic amphibolite ophiolite protolith along a ductile thrust which separates the two major nappe units muscovite within blastomylonitic metagranite lagoa augen gneiss in upper structural levels of the morais massif records 370 375 ma 40 ar 39 ar plateau ages muscovite within phyllinite developed along a ductile thrust separating the gneiss from the structurally underlying ophiolite nappe records a 375 ma age together the 40 ar 39 ar data suggest that a regionally significant early variscan amphibolite facies metamorphism occurred prior to c 385 390 ma early devonian this was associated with ductile imbrication of continental and ophiolite structural units with resultant formation of a composite nappe complex the composite nappe complex must have been maintained at relatively high structural levels throughout the remaining variscan evolution because there is no evidence for post 370 ma rejuvenation of intracrystalline argon systems in any of crystalline structural units examined this is in marked contrast to a significant late devonian c 330 ma locally high pressure metamorphism which is recorded in structurally underlying elements of the lower allochthon part of a foreland thrust complex composed of metasedimentary units with iberian protolith affinities together available chronologic constraints indicate emplacement of the previously assembled composite nappe complex into its present relative structural position at c 330 ma with resultant deformation and metamorphism of structurally underlying components of the iberian thrust complex

a statistical study on elf whistlers emissions and m 5 0 earthquakes in taiwan 1 in this paper we conduct statistical approaches to study the potential relation between elf whistlers emissions below 100 hz and 20 m 5 0 earthquakes occurred in taiwan in the period from 26 august 2003 to 13 july 2004 occurrence ratios of the elf whistler and elf emission of the entire study period are computed as the reference backgrounds our study shows that the elf whistlers and elf emissions during the earthquake period appear less and more frequently than their associated backgrounds respectively for the elf emission the larger earthquakes generally yield the higher occurrence ratios the statistical analyses confirm that the occurrence ratios of the elf emission significantly enhance 5 7 days before the earthquakes and are proportional to the earthquake magnitude but inversely to the distance from the observatory to the epicenter

geochemical and geochronological cross section of the deep variscan crust the cabo ortegal high pressure nappe northwestern spain the high pressure rocks of the cabo ortegal nappe and related massifs are represented by several tectonometamorphic units which underwent separate histories before regional overthrusting and amphibolite facies recrystallization at 380 ma the occurrence of final cooling is recorded by 40ar 39ar and rb sr mica ages of up to 350 ma u pb zircon dating and sm nd and rb sr isotope data together with ree and major and trace element geochemistry provide constraints on the timing of earlier tectonothermal events and the nature of the protoliths the earliest tectonothermal event occurred at 490 480 ma and corresponds to the emplacement of lree enriched magmas of probable calc alkaline affinity and their metamorphism in the granulite facies this occurred at approximately the same time as the eclogite facies metamorphism of morb like protholiths associated with basic to intermediate granulites together this suggests formation of syn accretion granulites in an active margin setting a second high grade metamorphic event is recorded at 420 ma in metasedimentary formations associated with eclogite like assemblages garnet omphacite plagioclase this event is possibly related to a collisional plate tectonic setting in a back arc basin the age and origin of the associated ultrabasic rocks remains unclear but a late pyroxenite vein has yielded an emplacement age of 390 ma

the origin of the variscan upper allochthons in the ortegal complex northwestern iberia sm nd isotopic constraints on the closure of the rheic ocean northwestern iberia preserves a stack of allochthons in which the vestiges of a suture zone generated during the variscan orogeny by the late paleozoic collision between laurussia and gondwana are exposed lower allochthons contain ordovician ophiolite known as the lower ophiolite and are structurally overlain by devonian ophiolite upper ophiolite which are in turn structurally overlain by allochthons containing high grade metamorphic rocks with continental affinities and late cambrian early ordovician protolith ages known as the upper units geochemical and sm nd isotopic data from the upper ophiolite and the structurally overlying upper units exposed in the ortegal complex of galicia show that these allochthons are derived from a variety of mantle and crustal sources and indicate that the suture zone juxtaposes a variety of oceanic assemblages the general isotopic characteristics of each assemblage are similar to allochthons in other variscan complexes in nw iberia suggesting that the allocht

remote sensing of atmospheric and ionospheric signals prior to the mw 8 3 illapel earthquake chile 2015 in the present study a number of atmospheric and some ionospheric anomalies are analyzed which were recorded prior to the mw 8 3 illapel earthquake of september 16 2015 this very large earthquake occurred in central chile close to the coast as the result of thrust faulting on the interface between the nazca plate and south american continent using remotely sensed data extracted from nasa giovanni noaa ncep and noaa ngdc atmospheric and ionospheric anomalies were observed that co registered 35 40 and 25 30 days prior to the main shock respectively with reference to long term time series over the epicentral area significant atmospheric anomalies were recorded for cloud cover geopotential height precipitation rates surface air pressure omega stream function and wind vectors all in the time window of august 5 10 2015 35 40 days prior to the main shock anomalous tec maps were recorded for the same time period satellite images indicate the formation of an unusual cyclone presumably triggered by air turbulences and abnormal atmospheric conditions over the epicentral area including strong vertical winds data from the jicamarca radio observatory in peru more than 2000 km to the north reveal anomalous ionospheric variations on august 15 20 2015 with respect to international reference ionosphere thickness parameters and the altitude of the f layer the observed anomalies are consistent with processes that occur at the ground to air interface due to the stress activation of peroxy defects in the hypocentral volume the flow of positive hole charge carriers to the earth surface expected to have led to massive air ionization generating at first primarily positive airborne ions then negative air ions plus ozone understanding the sequence of processes inside the earth s crust and at the ground to air interface provides information not previously available about the causal and temporal linkages between the various pre earthquake phenomena and the future seismic event

multisatellite observations of an intensified equatorial ionization anomaly in relation to the northern sumatra earthquake of march 2005 here we report multisatellite observations of ionospheric disturbances in relation to the occurrence of the m8 7 northern sumatra earthquake of 28 march 2005 the demeter detection of electro magnetic emissions transmitted from earthquake regions and champ challenging minisatellite payload satellite data were investigated to find possible precursory and postevent phenomena it was found that eia equatorial ionization anomaly strength expressed in the apex height derived from the champ plasma density profile was intensified along the orbits whose longitudes were close to the epicenter within about a week before and after occurrence of the earthquake increases in electron and o density along the orbits close to the epicenter were also observed in the demeter measurements the normalized equatorial plasma density derived from the demeter measurements showed intensification about a week before and after the earthquake reaching maximum the day after the shock and afterward disappearing in addition similar behavior of the eia enhancements related to the m8 0 pisco earthquake of 15 august 2007 was observed surveys of space weather and geomagnetic activities excluded the possibility that these fluctuations were caused by changes in space weather or by a geomagnetic storm statistical analyses of the longitudinal variation revealed that the eia was enhanced in the west of the epicenter and reduced in the east of the epicenter and this fits the increased conductivity model based on these observations we proposed a revised view of seismo ionospheric coupling in the region of the geomagnetic equator to explain the eia features observed in this study

reply to comment by f masci and j n thomas on temporal and spatial precursors in ionospheric total electron content of the 16 october 1999 mw7 1 hector mine earthquake

tracing crustal evolution in the nw iberian peninsula through the rbsr and upb systematics of palaeozoic granitoids a review abstract the abundant granitoids in the palaeozoic basement of the northwestern iberian peninsula include 470 440 ma old suites early middle ordovician now present as orthogneisses and several variscan suites the age data presently available suggest that the latter have been generated in three separate time intervals 330 320 ma ago late visean early namurian 310 300 ma ago westphalian and 290 280 ma ago late stephanian autunian rb sr whole rock and u pb zircon systematics along with field and chemical evidence testify to the generation of the early and late palaeozoic granitoids from lower palaeozoic and precambrian maximum age 1 7 1 6 ga sedimentary sequences respectively the source rocks contained zircons derived from a late archaean early proterozoic continental crust that probably underlies the whole of western europe although for the greater part modified beyond recognition by younger crustal reworking

u pb ages of detrital zircons from the internal betics a key to deciphering paleogeographic provenance and tectono stratigraphic evolution abstract zircons from the nevado filabride complex metamorphic rocks yielded 891 concordant inherited detrital ages the 342 concordant ages from the aulago fm indicate a pennsylvanian maximum depositional age while the age density distribution indicates that this formation is closely related to the cantabrian zone north of the iberian massif the dominant ediacaran and cryogenian populations at ca 596 and 788 ma respectively relate the nevado filabride complex to northern gondwana terranes a discrete mesoproterozoic zircon population at ca 1031 ma tonian late estenian population suggests that the basement of the nevado filabride complex could have been located near of the saharan metacraton and west of the east african orogen at the beginning of the paleozoic the 549 concordant ages from the tahal fm yield an early permian age for the protoliths the age density distribution pattern records erosion of rocks from the variscan belt including late variscan magmatic rocks zircon spectra differ from those of the alboran domain supporting the hypothesis that the nevado filabride complex is part of the south iberian domain furthermore data from the tahal fm are similar to those of permo triassic rocks from the iberian ranges

preearthquake anomalous ionospheric signatures observed at low mid latitude indian station delhi during the year 2015 to early 2016 preliminary results we have analyzed five major earthquake events measuring greater than 6 on richter scale m 6 that occurred during the year 2015 to early 2016 affecting indian region ionosphere using f 2 layer critical parameters f o f 2 h m f 2 obtained using digisonde from a low mid latitude indian station delhi 28 6 degrees n 77 2 degrees e 19 2 degrees n geomagnetic latitude 42 4 degrees n dip normal day to day variability occurring in ionosphere is segregated by calculating f 2 layer critical frequency and peak height variations delta f o f 2 h m f 2 from the normal quiet time behavior apart from computing interquartile range we find that the ionospheric f 2 region across delhi by and large shows some significant perturbations 3 4 days prior to these earthquake events resulting in a large peak electron density variation of similar to 200 these observed perturbations indicate towards a possibility of seismo ionospheric coupling as the solar and geomagnetic indices were normally quiet and stable during the period of these events it was also observed that the precursory effect of earthquake was predominantly seen even outside the earthquake preparation zone as given by dobrovolsky et al 1979 the thermosphere neutral composition o n 2 as observed by global ultraviolet imager across delhi during these earthquake events does not show any marked variation further the effect of earthquake events on ionospheric peak electron density is compared to the lower atmosphere meteorological phenomenon of 2015 sudden stratospheric warming event

statistical analysis of ulf seismomagnetic phenomena at kakioka japan during 2001 2010 to clarify and verify the ultralow frequency ulf seismomagnetic phenomena we have performed statistical studies on the geomagnetic data observed at the kakioka kak station japan during 2001 2010 we investigated the energy of ulf geomagnetic signals of the frequency around 0 01 hz using wavelet transform analysis to minimize the influences of artificial noises and global geomagnetic perturbations we used only the geomagnetic data observed at nighttime lt 2 30 a m to 4 00 a m and utilized observations from a remote station kanoya as a reference statistical results of superposed epoch analysis have indicated that ulf magnetic anomalies are more likely to appear before sizable earthquake events es 108 rather than after them especially 6 15 days before the events further statistical investigations show clearly that the ulf geomagnetic anomalies at kak station are more sensitive to larger and closer events finally we have evaluated the precursory information of ulf geomagnetic signals for local sizable earthquakes using molchan s error diagram the probability gain is around 1 6 against a poisson model the above results have indicated that the ulf seismomagnetic phenomena at kak clearly contain precursory information and have a possibility of improving the forecasting of large earthquakes

statistical evidences of seismo ionospheric precursors applying receiver operating characteristic roc curve on the gps total electron content in china abstract evidence of the seismo ionospheric precursor sip is reported by statistically investigating the relationship between the total electron content tec in global ionosphere map gim and 56 m 6 0 earthquakes during 1998 2013 in china a median based method together with the z test is employed to examine the tec variations 30 days before and after the earthquake it is found that the tec significantly decreases 0600 1000 lt 1 6 days before the earthquake and anomalously increases in 3 time periods of 1300 1700 lt 12 15 days 0000 0500 lt 15 17 days and 0500 0900 lt 22 28 days before the earthquake the receiver operating characteristic roc curve is then used to evaluate the efficiency of tec for predicting m 6 0 earthquakes in china during a specified time period statistical results suggest that the sip is the significant tec reduction in the morning period of 0600 1000 lt the sip is further confirmed since the area under the roc curve is positively associated with the earthquake magnitude

preliminary investigation of real time mapping of fof2 in northern china based on oblique ionosonde data 1 a real time mapping model of fof2 in northern china was established using neural networks nns to avoid the local minimum problem associated with traditional nns a newly improved genetic algorithm based nn ga nn was developed using the input parameters of solar activities geomagnetic activities neutral winds seasonal information and geographical coordinates the fof2 data were extracted by inversing the oblique ionograms obtained from the oblique ionosondes of the china ground based seismo ionospheric monitoring network every 30 min for the period from august 2009 to december 2011 the data associated with five transmitter stations beijing changchun qingdao xinxiang and suzhou and one receiver station in binzhou were considered the input parameters for the real time fof2 mapping model and the data from the dalian and jinyang transmitter stations were used to verify the results the jining transmitter station data were used to test the capability of the model the root mean square error and percent deviation were calculated to estimate the performance of the model the correlation coefficient was used to evaluate the correlation of observed and predicted values in addition observations of fof2 from the vertical ionosondes at beijing changchun qingdao and suzhou stations are compared with the model prediction of fof2 the results indicate that the developed real time fof2 mapping model based upon genetic algorithm based nn is very promising for ionospheric studies

tectonic evolution of variscan iberia gondwana laurussia collision revisited an integrated interpretation of the late paleozoic structural and geochronological record of the iberian massif is presented and discussed under the perspective of a gondwana laurussia collision giving way to the variscan orogen compressional and extensional structures developed during the building of the variscan orogenic crust of iberia are linked together into major tectonic events operating at lithosphere scale a review of the tectonometamorphic and magmatic evolution of the iberian massif reveals backs and forths in the overall convergence between gondwana and laurussia during the amalgamation of pangea in late paleozoic times stages dominated by lithosphere compression are characterized by subduction both oceanic and continental development of magmatic arcs over and under thrusting of continental lithosphere and folding variscan convergence resulted in the eventual transference of a large allochthonous set of peri gondwanan terranes the iberian allochthon onto the gondwana mainland the iberian allochthon bears the imprint of previous interaction between gondwana and laurussia including their juxtaposition after the closure of the rheic ocean in lower devonian times stages governed by lithosphere extension are featured by the opening of two short lived oceanic basins that dissected previous variscan orogenic crust first in the lower middle devonian following the closure of the rheic ocean and then in the early carboniferous following the emplacement of the peri gondwanan allochthon an additional major intra orogenic extensional event in the early middle carboniferous dismembered the iberian allochthon into individual thrust stacks separated by extensional faults and domes lateral tectonics played an important role through the variscan orogenesis especially during the creation of new tectonic blocks separated by intracontinental strike slip shear zones in the late stages of continental convergence

variations of ionospheric total electron content during the chi chi earthquake on 20 september1999 ut 21 septemberin local time lt a large earthquake mw 7 7 struck central taiwan nearthe small town of chi chi the greatest plasma frequency in the ionosphere fof2 observed by the chung li ionosonde 25 0 n 121 2 e reveals three clear precur sors at 1 3 and 4 days prior to the earthquake this paper examines the ionospheric total electron content tec ob served by a network of the global positioning system gps receivers in taiwan area it is found that variations in fof2 and overhead tec recorded at chung li have a similar ten dency combining the data of the network of 13 gps re ceivers time and spatial variations of tec prior to the chi chi earthquake are examined results show that the equa torial anomaly crest moves equatorward and its tec value significantly decreases 1 3 and 4 days before the earth quake a comparison between the disturbed and reference previous 15 day median days confirms that tec decreases significantly around the epicenter in the afternoons of these days finally possible mechanisms are proposed and dis cussed

time resolved study of charge generation and propagation in igneous rocks electrical resistivity changes ground potentials electromagnetic em and luminous signals preceding or accompanying earthquakes have been reported many times in addition to ground uplift and tilt and other parameters however no concept exists that would tie these diverse phenomena together into a physically coherent model using low to medium velocity impacts to measure electrical signals with microsecond time resolution it is observed that when gabbro and diorite cores are impacted at relatively low velocities 100 m s highly mobile charge carriers are generated in a small volume near the impact point they spread through the rocks causing electric potentials exceeding 400 mv em and light emission as the charge cloud spreads the rock becomes momentarily conductive when a granite block is impacted at higher velocity 1 5 km s the propagation of the p and s waves is registered through the transient piezoelectric response of quartz after the sound waves have passed the surface of the granite block becomes positively charged suggesting the same charge carriers as observed during the low velocity impact experiments expanding from within the bulk during the next 2 3 ms the surface potential oscillates indicating pulses of electrons injected from ground and contact electrodes the observations are consistent with positive holes e g defect electrons in the o2 sublattice traveling via the o 2p dominated valence band of the silicate minerals the positive holes propagate as charge clouds rather than as classical em waves before activation they lay dormant in form of electrically inactive positive hole pairs php chemically equivalent to peroxy links o3x oo xo3 with x si4 al3 etc phps are introduced into the minerals by way of hydroxyl o3x oh which all nominally anhydrous minerals incorporate when crystallizing in h2o laden environments the fact that positive holes can be activated by low energy impacts and their attendant sound waves suggests that they can also be activated in the crust by microfractures during the dilatancy phase depending on where in the stressed rock volume the charge carriers are activated they will form rapidly moving or fluctuating charge clouds that can account for earthquake related electrical signals and em emission wherever such charge clouds intersect the surface high fields are expected causing electric discharges and earthquake lights

a statistical study on the correlation between lower ionospheric perturbations as seen by subionospheric vlf lf propagation and earthquakes 1 the subionospheric vlf lf propagation is extensively used to investigate the lower ionospheric perturbation in possible association with earthquakes an extensive period of data over 7 yr from january 2001 to december 2007 and a combination of different propagation paths in and around japan are used to examine the statistical correlation between the vlf lf propagation anomaly average nighttime amplitude dispersion and nighttime fluctuation and earthquakes with magnitude 6 0 it is then found that the propagation anomaly exceeding the 2 standard deviation criterion indicating the presence of ionospheric perturbation is significantly correlated with earthquakes with shallow depth 40 km finally the mechanism of seismoionospheric perturbations is discussed

outline of upper precambrian and lower paleozoic evolution of the iberian peninsula according to u pb dating of zircons in the northwestern part of the iberian peninsula recent geological studies have defined the following stratigraphic sequence from bottom to top basal orthogneiss of miranda do douro is overlain by a complex of schist and greywacke which have been assigned to the cambrian or late precambrian these are followed by the ollo de sapo gneisses of volcanic sedimentary origin which in turn are overlain by the fossiliferous layers of the lower ordovician the schist and greywacke complex and the lower part of the ollo de sapo formation are transected by granitic dikes viana del bollo orthogneiss all these rocks were folded faulted metamorphosed and intruded by granite plutons during variscan times the emplacement of the miranda do douro and viana del bollo orthogneisses have been respectively dated at 618 9 ma and 465 10 ma by the u pb method on zircons these data yield lower and upper limits for the deposition of the ollo de sapo formation and demonstrate the occurrence of a precambrian basement pan african or cadomian orogeny in the variscan belt in the northwestern part of the iberian peninsula the emplacement of viana del bollo orthogneiss could be genetically related to the main phase of crustal thinning 470 520 ma characteristic of the prevariscan evolution of western europe typology and u pb data of the ollo de sapo zircons indicate the occurrence of inherited old precambrian zircons and yield an age of 325 3 ma for the variscan main thermal event in the area considered four possible evolutionary models for the u pb system of the ollo de sapo zircons are discussed

tectonic evolution of the careon ophiolite northwest spain a remnant of oceanic lithosphere in the variscan belt abstract analysis of the careon unit in the ordenes complex northwest iberian massif has supplied relevant data concerning the existence of a paleozoic oceanic lithosphere probably related to the rheic realm and the early subduction related events that were obscured along much of the variscan belt by subsequent collision tectonics the ophiolite consists of serpentinized harzburgite and dunite in the lower section and a crustal section made up of coarse grained and pegmatitic gabbros an early devonian zircon age documentclass aastex usepackage amsbsy usepackage amsfonts usepackage amssymb usepackage bm usepackage mathrsfs usepackage pifont usepackage stmaryrd usepackage textcomp usepackage portland xspace usepackage amsmath amsxtra usepackage ot2 ot1 fontenc newcommand cyr renewcommand rmdefault wncyr renewcommand sfdefault wncyss renewcommand encodingdefault ot2 normalfont selectfont declaretextfontcommand textcyr cyr pagestyle empty declaremathsizes 10

spatiotemporal characteristics of the geomagnetic diurnal variation anomalies prior to the 2011 tohoku earthquake mw 9 0 and the possible coupling of multiple pre earthquake phenomena abstract xu et al 2013 and han et al 2015 have reported unusual behaviors of geomagnetic diurnal variation gdv in the vertical component prior to the 2011 off the pacific coast of tohoku earthquake mw 9 0 to make a better understanding of this phenomenon temporal spatial analyses of gdv have been applied in this study geomagnetic data of long term observations at 17 stations in japan have been analyzed using the same method in han et al 2015 ratios of diurnal variation range between the reference station kak and the target stations have been computed after removing seasonal variations the 15 day backward running mean values of the ratios in the vertical component shows a clear anomaly exceeding the statistical threshold about 2 months before the mega event at both esa and miz stations in the tohoku region locations of anomalies in spatial distribution show a good correlation with the epicenter of the mw 9 0 earthquake these spatiotemporal results are consistent with those obtained from other independent observations such as groundwater level and gps displacements the coupling of multiple pre earthquake phenomena may help to understand the preparation process of a mega earthquake in the subduction zone

total electron content anomalies associated with global vei4 volcanic eruptions during 2002 2015 abstract in previous studies little attention has been paid to the total electron content tec anomalies preceding the volcanic eruption we analyze the coupling relationship between volcanic eruption and tec anomalies and discuss the spatial distribution of tec anomalies associated with volcanic geographical location we utilize the global ionosphere map gim data from the center for orbit determination in europe code to analyze tec variations before the global volcanic eruptions indicated by vei volcanic explosivity index 4 from 2002 to 2015 with the sliding interquartile range method the results indicate the occurrence rate of tec anomalies before great volcanic eruptions is related with the volcanic type and geographical position the occurrence rate of tec anomalies before stratovolcano and caldera eruptions is higher than that before shield and pyroclastic shield eruptions and the occurrence rate of tec anomalies has a descending trend from low latitudes to high latitudes the tec anomalies before the volcanic eruptions in low mid latitudes are within the volcanic affected areas but do not coincide with the volcanic foci the corresponding tec anomalies could be observed in the conjugated region and all the tec anomalies in the volcanic affected areas are usually close to bounds of equatorial anomaly zones however the tec anomalies preceding these eruptions in high latitudes usually surround the volcano and no tec anomalies appear in the conjugated region these conclusions have potential applications to the prediction of great volcanic eruptions in the future

statistical analysis of tec anomalies prior to m6 0 earthquakes during 2003 2014 there are many studies on the anomalous variations of the ionospheric tec prior to large earthquakes however whether or not the morphological characteristics of the tec anomalies in the daytime and at night are different is rarely studied in the present paper based on the total electron content tec data from the global ionosphere map gim we carry out a statistical survey on the spatial temporal distribution of tec anomalies before 1339 global m6 0 earthquakes during 2003 2014 after excluding the interference of geomagnetic disturbance the temporal and spatial distributions of ionospheric tec anomalies prior to the earthquakes in the daytime and at night are investigated and compared except that the nighttime occurrence rates of the pre earthquake ionospheric anomalies peias are higher than those in the daytime our analysis has not found any statistically significant difference in the spatial temporal distribution of peias in the daytime and at night moreover the occurrence rates of pre earthquake ionospheric tec both positive anomalies and negative anomalies at night tend to increase slightly with the earthquake magnitude thus we suggest that monitoring the ionospheric tec changes at night might be a clue to reveal the relation between ionospheric disturbances and seismic activities

highly depleted oceanic lithosphere in the rheic ocean implications for paleozoic plate reconstructions the rheic ocean formed at ca 500 ma when several peri gondwanan terranes e g avalonia and carolinia drifted from the northern margin of gondwana and were consumed during the late carboniferous collision between laurussia and gondwana a key event in the formation of pangea several mafic complexes ranging in age from ca 400 330 ma preserve many of the lithotectonic and or chemical characteristics of ophiolites they are characterized by anomalously high end values that are typically either between or above the widely accepted model depleted mantle curves these data indicate derivation from a highly depleted hd mantle and imply that i the mantle source of these complexes displays time integrated depletion in nd relative to sm and ii depletion is the result of an earlier melting event in the mantle from which basalt was extracted the extent of mantle depletion indicates that this melting event occurred in the neoproterozoic possibly up to 500 million years before the rheic ocean formed if so the mantle lithosphere that gave rise to the rheic ocean mafic complexes must have been captured from an adjacent older oceanic tract the transfer of this captured lithosphere to the upper plate enabled it to become preferentially preserved possible mesozoic cenozoic analogues include the capture of the caribbean plate or the scotia plate from the pacific to the atlantic oceanic realm our model implies that virtually all of the oceanic lithosphere generated during the opening phase of the rheic ocean was consumed by subduction during laurentia gondwana convergence

calcic amphibole equilibria and a new amphibole plagioclase geothermometer there is currently a dearth of reliable thermobarometers for many hornblende and plagioclase bearing rocks such as granitoids and amphibolites a semi empirical thermodynamic evaluation of the available experimental data on amphibole plagioclase assemblages leads to a new thermometer based on the aliv content of amphibole coexisting with plagioclase in silica saturated rocks the principal exchange vector in amphiboles as a function of temperature in both the natural and experimental studies is left na square 1 right a left alsi 1 right t1 we have analysed the data using 3 different amphibole activity models to calibrate the thermometer reactions 1 edenite 4 quartz tremolite albite 1 2 pargasite 4 quartz hornblende albite 2 the equilibrium relation for both 1 and 2 leads to the proposed new thermometer t frac 0 677p 48 98 y 0 0429 0 008314 ln k and k left frac si 4 8 si right x ab plag where si is the number of atoms per formula unit in amphiboles with p in kbar and t in k the term y represents plagioclase non ideality rtln ab from darken s quadratic formalism dqf with y 0 for xab 0 5 and y 8 06 25 5 1 xab 2 for xab 0 5 the best fits to the data were obtained by assuming complete coupling between al on the t1 site and na in the a site of amphibole and the standard deviation of residuals in the fit is 38 c the thermometer is robust to ferric iron recalculation procedures from electron probe data and should yield temperatures of equilibration for hornblende plagioclase assemblages with uncertainties of around 75 c for rocks equilibrated at temperatures in the range 500 1100 c the thermometer should only be used in this temperature range and for assemblages with plagioclase less calcic than an92 and with amphiboles containing less than 7 8 si atoms pfu good results have been attained on natural examples from greenschist to granulite facies metamorphic rocks as well as from a variety of mafic to acid intrusive and extrusive igneous rocks our analysis shows that the pressure dependence is poorly constrained and the equilibria are not suitable for barometry

a statistical investigation of preearthquake ionospheric anomaly 1 empirical evidence of the preearthquake ionospheric anomalies peias is reported by statistically investigating the relationship between variations of the plasma frequency at the ionospheric f2 peak fof2 and 184 earthquakes with magnitude m 5 0 during 1994 1999 in the taiwan area the peia defined as the abnormal decrease more than about 25 in the ionospheric fof2 during the afternoon period 1200 1800 lt significantly occurs within 5 days before the earthquakes moreover the odds of earthquakes with peia increase with the earthquake magnitude but decrease with the distance from the epicenter to the ionosonde station these results indicate that the peia is energy related

p t paths from high temperature shear zones beneath ophiolites mctamorphic rocks of the st anthony complex of north western newfoundland are best interpreted in terms of a high temperature shear zone formed between down going continental margin rocks and overriding oceanic lithosphere in a subduction zone high grade rocks immediately beneath the oceanic lithosphere peridotite display retrograde meta morphism in high strain zones whereas lower grade rocks near the base of the metamorphic complex display prograde metamorphism in high strain zones mylonite zones in meta basitcs at all levels in the complex contain the assemblage epidote hornblende albite sodic oligoclase these observations suggest that the inverted metamorphic gradient within the st anthony complex results from the fortuitous preservation of residual metamorphic assemblages from different crustal levels within an epidote amphibolite facies shear zone the degree of re equilibration is strongly dependent on the degree of strain and is best achieved in synmetamorphic mylonite zones this interpretation of the st anthony complex can be extended to other sub ophiolite metamorphic sheets which show very similar relationships it is proposed that most metamorphic sheets beneath ophiolites are high temperature shear zones the p t paths of which preserve records of burial and exhumation in subduction zones

correlation of the nappe stack in the ibero armorican arc across the bay of biscay a joint french spanish project a correlation between allochthonous units exposed in the nw iberian massif and the southern armorican massif is carried out based on lithological associations structural position age and geochemistry of protoliths and tectonometamorphic evolution the units on both sides of the bay of biscay are grouped into upper middle and lower allochthons whereas an underlying allochthonous thrust sheet identified in both massifs is referred to as the parautochthon the lower allochthon represents a fragment of the outermost edge of gondwana that underwent continental subduction shortly after the closure of a palaeozoic ocean which in turn is represented by the middle allochthon the latter consists of supra subduction ophiolites and metasedimentary sequences alternating with basic mid ocean ridge basalt morb type volcanics with inheritances suggesting the proximity of a continental domain seafloor spreading began at the cambro ordovician boundary and oceanic crust was still formed during the late devonian covering the lifetime of the rheic ocean which is possibly represented by the middle allochthon the opening of the oceanic domain was related to pulling apart the peri gondwanan continental magmatic arc which is represented by the upper allochthon

origin of the amphibolite sole of the josephine ophiolite emplacement of a cold ophiolite over a hot arc the amphibolite sole that occurs along the basal thrust of the josephine ophiolite madstone cabin thrust is distinct from those described for ophiolites such as the bay of islands and oman antigorite bearing serpentinite mylonites occur directly above the amphibolite and the presence of antigorite brucite indicates formation between 300 and 400 c the antigorite mylonites also contain relict lizardite chrysotile suggesting formation of antigorite by prograde metamorphism along the base of the ophiolite further evidence for prethrusting low temperature serpentinization comes from a lizardite chrysotile shear zone within fresh peridotite directly above the thrust that is cut by undeformed diabase dikes having geochemical affinities to the upper pillow lavas of the josephine ophiolite the prograde metamorphism of the serpentinite at the base of the ophiolite was apparently synchronous with greenschist facies retrogressive metamorphism of the underlying amphibolite the amphibolite is chemically diverse and has been divided into two groups group 1 amphibolite appears to be derived from mafic plutonic rocks and has immobile trace element abundances indicating affinities to volcanic arc magmas group 2 amphibolite is metavolcanic contains some quartzite and has magmatic affinities to mid ocean ridge basalt and within plate basalt an association that is distinctive of older basement rocks elsewhere in the western klamath terrane we suggest the amphibolite was derived from the footwall of the madstone cabin thrust including country rocks for the chetco complex group 2 and possibly older intrusive phases of the chetco complex itself group 1 previous workers have shown that the base of the amphibolite is intruded by gneissic gabbro of the chetco complex that intrusion of the chetco complex overlapped in time with deformation of the amphibolite and that during and after emplacement the josephine ophiolite and overlying flysch were intruded by abundant arc related dikes and plutons emplacement of the josephine ophiolite appears to have occurred by underthrusting of a cold ophiolite by an active magmatic arc

accretionary history and crustal evolution of the variscan belt in western europe abstract the variscan belt of western europe is part of a large intra paleozoic belt extending on both sides of the atlantic from the ouachitas in the us and the mauritanides in west africa to the bohemian massif in czechoslovakia and poland the belt was constructed between 500 and 250 ma as a result of convergence and collision between two main continents laurentia baltica and africa after the closure of various oceanic basins iapetus rheic and galicia massif central now recorded as discrete in part cryptic sutures which form the roots of large crystalline nappes in which are found dismembered remnants of oceanic crust and mantle the accretionary history of the variscan belt in western europe is related to the progressive closure of probably two oceanic basins the rheic in the north and another the galicia massif central in the south by respectively southward and northward intraoceanic subduction followed by obduction and intracontinental lithospheric subduction the result is a broad 700 800 km fan like divergent belt which must be considered as a classical obduction collision orogen with a long intracontinental history of about 100 150 ma its arcuate shape is probably due to the northwestward impingement of a promontory of the african continent into laurentia baltica

early ordovician orogenic event in galicia nw spain evidence from u pb ages in the uppermost unit of the ordenes complex new u pb data zircon monazite and rutile obtained from rocks of the uppermost allochthon in the variscan belt of nw spain indicate that the hangingwall to the suture includes an allochthonous unit with a pre variscan tectonothermal evolution this evolution is characterised by an early ordovician 498 500 ma bimodal magmatism followed almost immediately 493 498 ma by a barrovian style metamorphism up to the granulite facies the metamorphism subsequent to the igneous intrusions requires convergence and crustal thickening in order to generate the barrovian facies pattern shown by the lithologies of the uppermost allochthon the almost coeval magmatism and metamorphism and the chemistry of the metabasites suggest an accretionary complex probably related to a volcanic arc as the most probable setting for the origin of the uppermost unit the implications of the existence of early ordovician convergent plate boundaries are discussed in the context of gondwana laurentia avalon interactions

recent progress in ionospheric earthquake precursor study in china a brief review abstract the study of ionospheric anomaly variation before large earthquakes has attracted the attention of geophysicists for many years this is primarily because ionospheric anomaly variation has been considered to constitute one possible method to identify earthquake precursors since china covers several major earthquake zones it is critical for chinese scientists to study possible ionospheric earthquake precursors in this report we provide a brief summary of recent progress in the study of ionospheric earthquake precursors mainly from chinese mainland researchers as well as some other scientists this report focuses on 1 some case studies of ionospheric abnormal behaviors before some great earthquakes around the world e g m7 9 wenchuan earthquake m9 0 tohoku oki earthquake m7 0 haiti earthquake and 2 some statistical characteristics of ionospheric anomalies before earthquakes including their temporal and spatial distributions and the relationship with the forthcoming earthquake the above mentioned studies may provide some new and beneficial insights for the future study of ionospheric earthquake precursors

temporal and spatial precursors in the ionospheric global positioning system gps total electron content observed before the 26 december 2004 m9 3 sumatra andaman earthquake 1 we report seismo ionospheric precursors of anomalous decreases in the total electron content tec appearing day 5 prior to an m9 3 earthquake the largest one in the last five decades which occurred in sumatra andaman indonesia on 26 december 2004 sequences of global ionosphere maps of the tec derived from worldwide ground based receivers of the global positioning system gps are used to statistically study the temporal and spatial precursors of the earthquake it was found that the temporal precursor of the gps tec around the epicenter was significantly reduced during the afternoon period on d 5 before the earthquake the spatial precursors prominently persistently and simultaneously appear around the epicenter and its conjugate areas of the sumatra andaman earthquake

origin and emplacement of ophiolites ever since their recognition ophiolites have been a source of controversy although all workers have agreed upon their importance a number of conflicting schools of thought have become unified in the interpretation of ophiolite complexes as fragments of oceanic crust and mantle formed at spreading centers an expanded version of the penrose ophiolite definition is proposed herein called the ophiolite association taking into account rocks which bear upon the origin and significance of ophiolite complexes an ideal ophiolite association includes the following units from bottom to top 1 a crystalline basement and shallow water sedimentary sequence 2 a tectonic unit of thrust slices of continental margin and rise and abyssal sediments and or melange 3 a metamorphic unit as much as a few hundred meters thick generally with higher grade rocks over lower grade ones 4 ultramafic tectonite unit composed dominantly of multiply deformed peridotite dunite and minor chromitite 5 a cumulate complex ultramafic at the base grading to mafic or intermediate at the top 6 a noncumulus unit of varitextured gabbro and minor trondhjemite 7 a sheeted dike complex 8 an extrusive section of massive and pillowed flows and intercalated sediments 9 an abyssal or bathyal sediment sequence which may include radiolarian chert red pelagic limestone metalliferous sediments breccias and or pyroclastic deposits and 10 postemplacement deposits of laterite reef limestone or shallow marine or subaerial sediments this expanded ophiolite association allows greater precision in inferring original origin and emplacement some ophiolite complexes particularly in the tethys herein designated tethyan type exhibit units 1 2 3 and 4 whereas others particularly in the cordilleran belt herein termed cordilleran type lack units 1 2 3 and in places 4 the emplacement of the former probably occurred during collision of a passive margin with a subduction zone or incipient subduction zone emplacement of the cordilleran type generally is not clear cut the nature of the spreading center which produced a given ophiolite is indicated more clearly by the presence or absence of units 5 9 than by chemistry or mineralogy some ophiolite complexes lack complete sections and may have formed along transform faults others contain volcanic pyroclastic deposits instead of pelagic sedimentary sequence and probably formed within or near an arc several ophiolite complexes may have originated by conversion of a transform fault into a subduction zone such conversion may result from normal plate evolution or from major plate reorganization major times of ophiolite emplacements appear to correspond with global plate reorganizations

nonlinear principal component analysis in the detection of ionospheric electron content anomalies related to a deep earthquake 300 km m 7 0 on 1 january 2012 izu islands japan 1 nonlinear principal component analysis nlpca and image processing are used to detect an ionospheric total electron content tec anomaly above japan s izu islands relating to an earthquake on 1 january 2012 ut mw 7 0 this earthquake was 348 km deep the earthquake occurred at 05 27 54 ut nlpca is applied to the time period 06 40 to 12 00 ut nlpca shows that the tec anomaly is highly localized and decreases in intensity with time pca was unable to detect the anomaly this work discusses potential reasons for the tec anomaly over the izu islands after this earthquake and possible reasons including acoustic gravity waves radon gas release and p type semiconductor effects

two new geobarometers for garnet amphibolites with applications to southeastern vermont two new geobarometers for the assemblage garnet hornblende plagioclase quartz have been calibrated on the basis of the equilibrium 6 anorthite 3 tremolite 2 grossular 1 pyrope 3 tschermakite 6 quartz and its fe end member equivalent data representing 37 natural samples that equilibrated at conditions of 2 5 to 13 kbar and 500 to 800 c were fitted to the general equation rt in keq a bt p i c by using a weighted least squares method multiple correlation coefficients are high 0 98 and 0 97 lines of constant keqhave extremely shallow slopes in p t space 2 to 8 bars per degree suggesting that pressures may be deduced precisely even where temperatures are only poorly constrained typical analytical errors and temperature imprecisions propagate to very small errors in pressure about 500 bars caution is advised in applying the barometers outside the range of calibrant mineral compositions application of the calibrations to samples from southeastern vermont near the strafford chester and athens domes documents relatively high pressure metamorphism 7 to 10 kbar for these structures

gravity and magnetic anomalies in the allochthonous ordenes complex variscan belt northwest spain assessing its internal structure and thickness 1 the ordenes complex is the largest variscan allochthonous structure of nw iberia and preserves the suture of a long standing paleozoic ocean probably the rheic gravity and magnetic data the latter specifically acquired on land for this study show that the complex occupies the core of an open synform with a maximum depth of 9 10 km which contrasts with the flat geometry of the lower crust and moho discontinuity beneath the maximum depth reached by the ophiolitic rocks marking the suture is around 7 km the allochthonous units formed by basic and ultrabasic rocks are lens shaped in section and occur not only at the periphery of the complex but form wide ribbons trending ne sw to n s the bouguer anomaly related with the longest of them the fornas unit previously used to support an autochthonous interpretation of the complexes is modeled as a rootless massive amphibolite body with a maximum thickness of 6 km located at the downthrown block of a large normal fault cutting across previous thrust faults and extensional detachments the main magnetic anomalies are associated with ultrabasic rocks cropping out in the nw and se but a weak wide anomaly in the central part of the complex is related with one or more thin layers of amphibolite partly mineralized with massive sulphides the weakly arcuate geometry of this anomaly and of the bouguer anomaly caused by the fornas unit may reflect the ne flank of the central iberian arc an orocline whose core is occupied by the allochthonous complexes

microstructure of serpentinite mylonites from the josephine ophiolite and serpentinization in retrogressive shear zones california the josephine peridotite has experienced deformational episodes over a wide range of temperatures deformation within the stability field of a serpentine group mineral appears invariably accompanied by retrogressive metamorphism serpentinization two general types of deformed serpentinites have been identified 1 incohesive serpentinites most common which appear to have experienced low temperature predominantly brittle deformation and 2 serpentinite mylonites which have experienced plastic flow near the upper limit of antigorite stability the distinction between these two is based on textural and mineralogical criteria serpentinite mylonites are cohesive homogeneously foliated and typically strongly lineated rocks composed primarily of antigorite and magnetite they occur in planar bounded zones enclosed within the josephine peridotite that were the loci of both noncoaxial deformation and serpentinization we discuss the development of two important shear sense indicators porphyroclast systems and oblique shear band foliations as observed in these rocks porphyroclast systems in serpentinite mylonites are often comprised of cores and mantles of different mineralogy cores are usually composed of primary pyrogenetic minerals whereas mantles including tails are composed of products of the serpentinization reaction these systems are therefore termed porphyroctasts with neocrystallization tails oblique shear bands are common micro structures in serpentinite mylonites shear bands which offset the mylonitic foliation along narrow discrete fractures are termed f type whereas those which offset the mylonitic foliation along narrow ductile micro shear zones are termed d type the latter are considered more reliable for shear sense determinations strains accomplished by movement on shear bands are probably small strain resulting from a volume increase dur ing serpentinization while holding the shear zone width constant is sufficient to produce the shear bands therefore we suggest that oblique shear bands may develop to accom modate volume increases associated with deformation

new insights into the appalachian orogen from geology and geochronology along the cape ray fault zone southwest newfoundland reverse oblique overthrusting of high grade port aux basques gneiss over the lower grade supracrustal windsor point group along the cape ray fault zone occurred during late silurian to early devonian time and is attributed to major oblique collision between gondwanan and laurentian continental blocks new u pb zircon 40 ar 39 ar and k ar data limit the timing of this orogenic event the megacrystic granitic phase of the cape ray igneous complex and the cape ray tonalite have been dated at 488 3 ma and 469 2 ma respectively a black rhyolite from the windsor point group yielded an ordovician age 453 5 4 ma a pretectonic gabbro sill within the windsor point group dated at 424 4 3 ma is cut by the windowglass hill granite dated at 424 2 ma synkinematic hornblende and biotite from the grand bay complex mylonites of the port aux basques gneiss have 40 ar 39 ar ages of 407 4 ma and 403 4 ma respectively which is indicative of a late silurian early devonian age for the amphibolite grade deformation these ages are compatible with a previously determined 415 ma monazite age interpreted as the time of peak metamorphism in the port aux basques gneiss and suggests rapid exhumation the east west flexure of the cape ray fault zone represents a tear fault accommodating differential shortening between the cape ray fault zone and the correlative fault system in central newfoundland mid devonian granites 386 3 384 2 ma intervene between the thrusting events and a younger sinistral transcurrent movement this deformation and magmatic history can be correlated throughout the northern appalachians along other major fault boundaries

gradual reduction in ionospheric f 2 region before the 2013 lushan earthquake contributed to the forthcoming earthquake or solar activity ionospheric anomalies before earthquakes during geomagnetic quiet conditions have been extensively discussed due to the importance of earthquake prediction however because of the high variability of ionosphere a real caution should be adopted before attributing the observations to seismo ionospheric precursors sips in an investigation of contradictory results in ionospheric variation before 2013 lushan earthquake we examine the ionospheric variation versus solar activity in order to assess the influence of solar activity of 27 day periodicity on ionospheric variation a quadratic regression model is developed by using the data of f2 layer critical frequency fof2 in april of 2008 2014 using the model ionospheric variation before the 2013 lushan earthquake is analyzed the results show that fof2 was strongly correlated with solar activity index f10 7 and had a low correlation with the remaining by eliminating the contribution of solar radiation which indicates that the gradual reduction in fof2 before the earthquake was contributed to the variation of solar radiation rather than the forthcoming earthquake

seismo ionospheric signatures prior to m 6 0 taiwan earthquakes this paper examines variations of the greatest plasma frequency in the ionosphere fof2 recorded by the chung li ionosonde 25 0 n 121 1 e before m 6 0 earthquakes during 1994 1999 the 15 day running median and the associated inter quartile range are utilized as the reference and the upper or lower bounds to monitor the ionospheric fof2 variations for finding seismo ionospheric signatures precursors of the earthquakes it is found that precursors in the form of the recorded fof2 falling below its associated lower bound around 1200 1700 lt appear 1 6 days prior to these earthquakes on september 20 1999 ut september 21 taiwan local time a large mw 7 7 earthquake struck central taiwan near the small town of chi chi we analyzed the fof2 and found three clear precursors 1 3 and 4 days prior to the chi chi earthquake

multi precursory analysis of phalla earthquake july 2015 mw 5 1 near islamabad pakistan the recent scientific progress in understanding the hierarchical nature of the lithosphere and its dynamics based on systematic earthquake monitoring helps in designing an improved earthquake forecasting strategy this study presents a detailed multi precursory analysis of a shallow moderate phalla earthquake july 24 2015 mw 5 1 depth 10 km near islamabad pakistan 24 km away from the monitoring site within the context of earthquake forecasting the instrumental setup soil radon monitor and space ground based ionosonde for precursory monitoring of earthquake activity is installed at the foothills of margalla along the main boundary thrust for identification of abnormal behavior of ionospheric parameters and soil radon flux a statistical criterion consistent with other studies is used our analyses reveal the effect of pre and co seismic changes in the form of anomalous behavior of local ionospheric perturbations 2 15 days prior soil radon flux 3 days prior and seismic quiescence related to phalla earthquake the solar geomagnetic conditions and meteorological parameters remained normal during the anomalous periods moreover multi precursory approach adopted in this study for earthquake prediction forecasting can serve as a potential indicator of seismic activity

rheic ocean ophiolitic remnants in southern iberia questioned by shrimp u pb zircon ages on the beja acebuches amphibolites 1 the rheic ocean was a major oceanic domain between avalonia and gondwana in ordovician silurian times most of the paleozoic plate reconstructions assume that the rheic ocean suture lies within southern iberia coinciding with the contact between the south portuguese zone and the ossa morena zone this paper reports four sensitive high resolution ion micro probe shrimp u pb zircon ages from mid ocean ridge basalt morb featured rocks of the beja acebuches amphibolite unit which crops out along the boundary between the ossa morena and the south portuguese zone and is considered its most conspicuous suture unit the obtained ages range from 332 3 to 340 4 ma corresponding to the crystallization of the mafic protoliths these early carboniferous ages for the beja acebuches amphibolites imply that this unit can no longer be viewed as an ophiolite belonging to the rheic ocean suture since this oceanic domain was presumably closed in devonian times tectonic reconstructions joining in a single suture line the beja acebuches amphibolite unit in southern iberia to either the devonian lizard ophiolite in southern england or the root zone of the devonian ordovician ophiolitic units in northwest iberia must be therefore reconsidered because of the age difference we interpret the beja acebuches amphibolite unit to represent a narrow and very ephemeral realm of oceanic like crust that opened in early carboniferous times after total consumption of the rheic ocean we suggest that a mantle plume underneath southern iberia in early carboniferous times is the most plausible large scale geodynamic scenario for the formation of these morb featured rocks

suspected seismo ionospheric coupling observed by satellite measurements and gps tec related to the m7 9 wenchuan earthquake of 12 may 2008 anomalous changes in the ionospheric conditions related to the wenchuan earthquake of 12 may 2008 are investigated using electron density ne from detection of electro magnetic emissions transmitted from earthquake regions demeter and champ satellites electric field from demeter and gps total electron content tec maps the normalized ne from the demeter satellite reveal that the previously reported tec increments before the earthquake can be considered as fragments of the gradual equatorial ionization anomaly eia enhancements near the epicenter longitude that began approximately 1 month before the earthquake and reached its maximum with an exceptionally large strength index 8 days prior to the main shock this feature is indirectly confirmed through the champ ne and gps tec data following the eia intensity peak disturbances in the ne and o density were observed in the nightside based on the concurrent electric field and ne changes it is suggested that eia intensification could be triggered by the e field disturbances over the epicenter

formation and emplacement of the josephine ophiolite and the nevadan orogeny in the klamath mountains california oregon u pb zircon and 40ar 39ar geochronology cordilleran ophiolites typically occur as basement for accreted terranes in the klamath mountains ophiolitic terranes were progressively accreted by underthrusting beneath north america the josephine ophiolite is the youngest of the klamath ophiolites and forms the basement for a thick late jurassic flysch sequence galice formation this ophiolite flysch terrane forms an east dipping thrust sheet sandwiched between older rocks of the klamath mountains above and a coeval plutonic volcanic arc complex below the outcrop pattern of the roof orleans thrust indicates a minimum displacement of 40 km and geophysical studies suggest 110 km of displacement the basal madstone cabin thrust is associated with an amphibolitic sole and has a minimum displacement of 12 km a rapid sequence of events from ophiolite generation to thrust emplacement has been determined using 40 ar 39 ar and pb u geochronology ophiolite generation occurred at 162 164 ma a thin hemipelagic sequence was deposited from 162 to 157 ma and flysch deposition took place between 157 and 150 ma tight age constraints on thrusting and low grade metamorphism associated with ophiolite emplacement nevadan orogeny are provided by abundant calc alkaline dikes and plutons ranging in age from 151 to 139 ma deformation and metamorphism related to the nevadan orogeny appears to have extended from 155 to 135 ma most of the crustal shortening took place by thrusting constrained to have occurred from 155 to 150 ma on both the roof and basal thrusts minimum rates of displacement are 2 4 and 3 6 mm year for the basal and roof thrusts respectively but correlations with coeval thrusts yield rates of 8 4 and 22 mm year within the range of plate velocities the high displacement rates and synchronous movement along the basal and roof thrusts suggest that the ophiolite may have behaved as a microplate situated between western north america and an active arc from 155 to 150 ma a steep thermal gradient was present in the josephine galice thrust sheet from 155 to 150 ma with amphibolite facies conditions developed along the basal thrust after accretion of the ophiolite by underthrusting the ophiolite and overlying flysch underwent low grade dynamothermal regional metamorphism from 150 to 135 ma the upper age limit is tightly constrained by a 135 ma k feldspar cooling age syntectonic plutons as young as 139 ma and a lower cretaceous angular unconformity very rapid exhumation is indicated by the late valanginian to hauterivian age 130 ma of the unconformably overlying strata suggesting unroofing by extensional tectonics

isotope geochemistry and revised geochronology of the purrido ophiolite cabo ortegal complex nw iberian massif devonian magmatism with mixed sources and involved mesoproterozoic basement abstract in the purrido ophiolite cabo ortegal complex new u pb zircon dating of the amphibolite g03 8 by laser ablation inductively coupled plasma mass spectrometry confirms the existence of a dominant mesoproterozoic zircon population with a refined age of 1155 14 ma however the u pb zircon dating of two more amphibolite samples by sensitive high resolution ion microprobe has provided new ages of 395 3 ma and 395 2 ma respectively interpreted as the crystallization age hf isotope data for zircon show that most of the devonian zircons crystallized from a juvenile depleted mantle source the mesoproterozoic zircons have relatively juvenile hf isotopic composition reflecting some influence of an older component a few devonian zircon crystals show evidence of mixing with an older component represented by the mesoproterozoic zircons the whole rock sm nd isotope data indicate an important heterogeneity in the composition of the purrido amphibolites only compatible with the generation of their protoliths from two sources we interpret these puzzling data as resulting from the mixing of a devonian mantle derived magma with a mesoproterozoic basement these new data provide new perspectives in the interpretation of the most common ophiolites across the variscan suture in europe supplementary material analytical methods zircon u th pb shrimp analytical data zircon u th pb la icp ms analytical data zircon lu hf la mc icpms analytical data and whole rock sm nd isotope data are available at http www geolsoc org uk sup18449

on the interpretation of peak metamorphic temperatures in light of garnet diffusion during cooling abstract finite difference models of fe mg diffusion in garnet undergoing cooling from metamorphic peak conditions are used to infer the significance of temperatures calculated using garnet biotite fe mg exchange thermometry for rocks cooled from high grades where the garnet was initially homogeneous the calculated temperature tcalc using garnet core and matrix biotite depends on the size of the garnet the ratio of garnet to biotite in the rock vgarnet vbiotite and the cooling rate for garnets with radii of 1 mm and vgarnet vbiotite 1 tcalc is 633 700 and 777 c for cooling rates of 1 10 and 100 c ma for vgarnet vbiotite 1 and 4 and a cooling rate of 10 c ma tcalc is approximately 660 and 610 c respectively smaller and larger garnets have lower and higher tcalc respectively these results suggest that peak metamorphic temperatures may be reliably attained from rocks crystallized at conditions below tcalc of the garnet core provided that vgarnet vbiotite is sufficiently small 0 1 and that the composition of the biotite at the metamorphic peak has not been altered during cooling numerical experiments on amphibolite facies garnets with nominal peak temperatures of 550 600 c generate a well in fe fe mg near the rim during cooling maximum calculated temperatures for the assemblage garnet chlorite biotite muscovite plagioclase quartz using the fe fe mg at the bottom of the well with matrix biotite range from 23 43 c to 5 12 c below the peak metamorphic temperature for cooling rates of 1 and 100 c ma respectively maximum calculated temperatures for the assemblage garnet staurolite biotite muscovite plagioclase quartz are approximately 70 c below the peak metamorphic temperature and are not strongly dependent on cooling rate the results of this study indicate that it may be very difficult to calculate peak metamorphic temperatures using garnet biotite fe mg exchange thermometry on amphibolite facies rocks tmax 550 c because the rim composition of the garnet which is required to calculate the peak temperature is that most easily destroyed by diffusion

seismoionospheric gps total electron content anomalies observed before the 12 may 2008 mw7 9 wenchuan earthquake 1 the global ionospheric map gim is used to observe variations in the total electron content tec of the global positioning system gps associated with 35 m 6 0 earthquakes that occurred in china during the 10 year period of 1 may 1998 to 30 april 2008 the statistical result indicates that the gps tec above the epicenter often pronouncedly decreases on day 3 5 before 17 m 6 3 earthquakes the gps tec of the gim and electron density profiles probed by six microsatellites of formosat3 cosmic f3 c are further employed to simultaneously observe seismoionospheric anomalies during an mw7 9 earthquake near wenchuan china on 12 may 2008 it is found that gps tec above the forthcoming epicenter anomalously decreases in the afternoon period of day 6 4 and in the late evening period of day 3 before the earthquake but enhances in the afternoon of day 3 before the earthquake the spatial distributions of the anomalous and extreme reductions and enhancements indicate that the earthquake preparation area is about 1650 km and 2850 km from the epicenter in the latitudinal and longitudinal directions respectively the f3 c results further show that the ionospheric f2 peak electron density nmf2 and height hmf2 significantly decreases approximately 40 and descends about 50 80 km respectively when the gps tec anomalously reduces

relationships between syn orogenic sedimentation and nappe emplacement in the hinterland of the variscan belt in nw iberia deduced from detrital zircons flysch type syn orogenic deposits of carboniferous age occur in relation to the emplacement of a large allochthonous nappe stack in the variscan belt of nw iberia new u pb age populations of detrital zircons obtained using laser ablation inductively coupled plasma mass spectrometry la icp ms are considered together with others from previously dated samples to establish the relationships between sedimentation and thrusting the age populations of four syn orogenic formations are compared with those of the pre orogenic sequence in the autochthon and parautochthon representing the gondwanan passive margin and in the allochthon formed by peri gondwanan and oceanic terranes in addition a new structural study has been carried out to understand the relationships between the syn orogenic deposits and the development of variscan structures the aims are to identify the sources of sediments and to establish the relationship between variscan structural evolution and syn orogenic sedimentation development of a forebulge outwards from the allochthonous front deduced from the structural study suggests the existence of depocentres that hosted the syn orogenic sediments together with the trend shown by the more recent zircons in each formation that are younger towards the external zones the data suggest that sedimentation occurred in progressively migrating depocentres formed in front of the allochthonous wedge during its emplacement the zircon age populations point to the allochthon as the main source of detritus for the syn orogenic basins with perhaps a limited participation of the parautochthon and autochthon in the younger formations

extensional flow produces recumbent folds in syn orogenic granitoids padron migmatitic dome nw iberian massif this contribution provides a case example on the generation of large scale recumbent folds in syn orogenic granitoids we analyze the progressive reworking of extension related structures into later ones after a period of crustal thickening the padron migmatitic dome formed after the climax of the gondwana laurussia collision in the late paleozoic petrostructural analysis carried out in the eastern flank of this dome reveals that extensional flow resulted in progressive exhumation of mainland gondwana which rested under peri gondwanan allochthonous terranes and a suture zone during maximum crustal thickening exhumation proceeded up to upper crust levels andalusite stability field along with partial melting of the middle lower crust and with the generation of granitoid laccoliths during an early extensional stage newly formed lithological and mechanical anisotropies such as the presence of variably sized sheet shaped bodies of syn orogenic granitoids provided a favorable rheological setting for fold nucleation during the intermediate stages of extension in extending orogenic crust whether recumbent folds occur after significant melt production depends on the lateral vertical flow ratio and on the orientation of deforming bodies with regard to kinematic strain axes we suggest that subhorizontal extensional flow dominated over vertical flow during the early and intermediate stages of the evolution of the padron dome a component of vertical diapiric flow caused progressive tilting of the sheet like bodies and obliquity respect to strain axes this resulted in the development of regional scale folds at the expense of syn orogenic granitoids such as in the case of the portomouro recumbent synform extensional ductile flow was oblique to the trend of the orogen during the whole process and directed to the nnw during the formation of recumbent folds non coaxial shearing favored an nnw sse elongate shape for the syn kinematic granitic massifs as well as the subsequent nucleation of recumbent folds deformation concentrated along discrete detachments during the late stages of extension

observations and simulations of seismoionospheric gps total electron content anomalies before the 12 january 2010 m7 haiti earthquake 1 in this paper the total electron content tec of the global ionosphere map gim is used to detect seismoionospheric anomalies associated with the 12 january 2010 m7 haiti earthquake and an ionospheric model is applied to simulate the detected anomalies the gim temporal variation shows that the tec over the epicenter significantly enhances on 11 january 2010 1 day before the earthquake the latitude time tec ltt plots reveal three anomalies 1 the northern crest of equatorial ionization anomaly eia moves poleward 2 the tecs at the epicenter and its conjugate increase and 3 the tecs at two dense bands in the midlatitude ionosphere of 35 n and 60 s further enhance the spatial analysis demonstrates that the tec enhancement anomaly appears specifically and persistently in a small region of the northern epicenter area the simulation well reproduces the three gim tec anomalies which indicate that the dynamoelectric field of the ionospheric plasma fountain might have been perturbed by seismoelectric signals generated around the epicenter during the earthquake preparation period

challenges in the detection of ionospheric pre earthquake total electron content anomalies peta for earthquake forewarning various studies have investigated the link between seismic activity and ionospheric precursory phenomena many of these retrospective case studies have supported the existence of pre earthquake ionospheric anomalies by examining past earthquake events using a variety of analytical methods based on existing methodologies however the conversion of a retrospective analysis to a prospective forewarning scenario is not a straightforward process the obstacles to its potential adoption stem mainly from assumptions made during data analysis and interpretation in this study several parameters pertaining to existing approaches for the detection of these ionospheric anomalies are highlighted and discussed in particular ionosphere total electron content tec a detailed examination is conducted to understand the roles that each of these parameters play in the detection process and the consequent difficulties when adopting them in a prospective analysis these issues include accounting for variations in ionosphere characteristics owing to different measurement platforms e g ground and space based observations and statistical methods e g standard deviation envelopes used in detecting anomalies furthermore the necessity of excluding space weather contributions in the underlying tec fluctuations poses a challenge in determining the validity of observed ionospheric anomalies the notion of an earthquake preparation zone is also evaluated in the context of the ionosphere along with its implications in a forewarning scenario these issues need to be addressed in current research in order to enable its possible application in earthquake forewarning

re interpreting the devonian ophiolites involved in the variscan suture u pb and lu hf zircon data of the moeche ophiolite cabo ortegal complex nw iberia new u pb zircon data of a mylonitic greenschist from the moeche ophiolite one of the mafic units involved in the variscan suture in the cabo ortegal complex nw of the iberian massif yielded an age of 400 3 ma consequently this unit can be considered one of the devonian ophiolites the most extended group of oceanic units in the variscan belt the mafic rocks show transitional compositions between n morb and island arc tholeiites although lu hf isotope signatures of its zircons clearly indicate contribution from an old continental source ehf values in the analysed zircons are negative generally below ehf 5 and thence they are not compatible with their generation from a juvenile mantle source accordingly the igneous protoliths were generated in a setting where juvenile mafic magmas interacted with an old continental crust the devonian ophiolites from the variscan suture have been repeatedly interpreted as remnants of the rheic ocean however the presence of a continental source in the origin of the mafic rocks of the moeche ophiolite allows discarding an intraoceanic setting for their generation at least for the nw iberian counterparts the tectonic setting for the devonian ophiolites of nw iberia is very likely represented by an ephemeral oceanic basin opened within a continental realm herein the real rheic ocean suture could only be located west of the terrane represented by the upper units of the allochthonous complexes apparently that suture is not represented in nw iberia

long term rst analysis of anomalous tir sequences in relation with earthquakes occurred in greece in the period 2004 2013 real time integration of multi parametric observations is expected to accelerate the process toward improved and operationally more effective systems for time dependent assessment of seismic hazard t dash and earthquake short term from days to weeks forecast however a very preliminary step in this direction is the identification of those parameters chemical physical biological etc whose anomalous variations can be to some extent associated with the complex process of preparation for major earthquakes in this paper one of these parameters the earth s emitted radiation in the thermal infrared spectral region is considered for its possible correlation with m 4 earthquakes occurred in greece in between 2004 and 2013 the robust satellite technique rst data analysis approach and robust estimator of tir anomalies retira index were used to preliminarily define and then to identify significant sequences of tir anomalies sstas in 10 years 2004 2013 of daily tir images acquired by the spinning enhanced visible and infrared imager on board the meteosat second generation satellite taking into account the physical models proposed for justifying the existence of a correlation among tir anomalies and earthquake occurrences specific validation rules in line with the ones used by the collaboratory for the study of earthquake predictability csep project have been defined to drive a retrospective correlation analysis process the analysis shows that more than 93 of all identified sstas occur in the prefixed space time window around m 4 earthquake s time and location of occurrence with a false positive rate smaller than 7 molchan error diagram analysis shows that such a correlation is far to be achievable by chance notwithstanding the huge amount of missed events due to frequent space time data gaps produced by the presence of clouds over the scene achieved results and particularly the very low rate of false positives registered on a so long testing period seems already sufficient at least to qualify tir anomalies identified by rst approach and retira index among the parameters to be considered in the framework of a multi parametric approach to t dash

a new model for the hercynian orogen of gondwanan france and iberia abstract the hercynian orogen of gondwanan france and iberia is a collage of disparate terranes separated by faults plate reconstructions indicate that the orogen developed during a massive dextral transpression as laurentia slid along the boundary of gondwana and as laurentia baltica and east avalonia rotated clockwise to form pangea it is proposed therefore that the collage is the result of this transpression and that it is an amalgamation of displaced tectonostratigraphic terranes which represent the dismembering of the gondwanan shelf with its stable platform ordovician devonian sedimentary sequence and the neighbouring rheic ocean specifically it is proposed that 1 the slice of the gondwanan shelf that now forms north brittany was displaced dextrally from nw africa around iberia by more than 2000 km 2 the ophiolites oceanic material and volcanic arcs of south armorica and the massif central represent slices of the rheic ocean displaced dextrally along the gondwana margin and shuffled in amongst slices of gondwanan shelf 3 the convergent component of the transpression is represented by thrusts throughout the region the leon terrane of france and ophiolite bearing klippe in nw iberia the ibero armorican arc was formed by wrapping the mobile dextral shear belts about a rigid iberian basement block the dextral porto tomar shear zone represents the more important shearing in iberia and the iberian sinistral shears are interpreted as bookshelf type structures subsidiary to the dextral shearing

a non cylindrical model for the northwest iberian allochthonous terranes and their equivalents in the hercynian belt of western europe abstract a case is made for a non cylindrical development of the european hercynian belt far travelled allochthonous terranes in the belt consist of a mixture of units including catazonal units ophiolites and units derived from the continental margin of gondwana they often depict a metamorphic history of intermediate to high pressure type and caledonian to eo hercynian age and are thought to have been put together in the early stages of the orogeny through a process partly obductive directed onto the continental margin of gondwana considerations upon the disposition of the terranes their relationships with the paleogeography of the gondwana realm and the structures in them suggest that their emplacement took place in an oblique fashion at a small angle to the margin of the continent the proposed allochthon could be related to the development of an island arc or a wedge like subplate in the southern part of the baltica plate later convergence between gondwana and laurussia involving transcurrent mostly dextral movements combined with tectonic escape phenomena would account for the present complexity of the belt and for the narrow strip the allochthonous terranes delineate in westernmost europe

geochemical evolution of high pressure mafic granulites from the bacariza formation cabo ortegal complex nw spain an example of a heterogeneous lower crust the cabo ortegal complex northwestern iberian massif is a klippen formed of several structural units stacked during the hercynian collision all these units include ultramafic rocks metabasites and quartz feldspathic gneisses affected by different metamorphic conditions the bacariza formation is heterogeneous showing a conspicuous layering mainly defined by alternate high pressure ultrabasic to basic granulites retrogressed garnet amphibolites of intermediate composition and rare acid rocks forming garnet trondhjemitic gneisses this layering is inherited from a gabbroic protolith showing a composition rich in fe and ti major and trace elements of these rocks can be correlated to continental tholeiitic series of extensional settings these high pressure granulites are situated in normal contact between serpentinised ultramafic rocks and other high grade metabasites with lessevolved and more depleted composition comparable to t type and n type morb it is suggested that the layered gabbro type protolith was part of a continuous mafic crust this crust was initially formed during early ordovician in a continental extensional setting and progressively evolved to oceanic spreading

careon ophiolite nw spain suprasubduction zone setting for the youngest rheic ocean floor the careon ophiolite galicia nw iberian massif shows lithological and geochemical features suggestive of an origin in a suprasubduction zone setting as with other devonian ophiolites in the european variscan belt it was generated within a contracting rheic ocean this setting and the general absence of large silurian devonian volcanic arcs on both of the rheic ocean margins strongly suggest that this ocean was closed by intraoceanic subduction directed to the north this subduction removed the older normal n mid oceanic ridge basalt morb oceanic lithosphere and gave rise to a limited volume of new suprasubduction zone oceanic lithosphere the careon ophiolite is a key element in understanding the evolution of the rheic ocean which was the main oceanic domain that closed during the paleozoic convergence of gondwana and laurussia preceding the assembly of pangea

structural and kinematic analysis of the corredoiras detachment evidence for early variscan synconvergent extension in the ordenes complex nw spain an important detachment is described in the allochthonous ordenes complex in the nw iberian massif and its meaning is related to the kinematics of contemporaneous convergent structures the corredoiras detachment cd separates a hangingwall unit characterised by a medium pressure metamorphic gradient from a footwall high pressure and high temperature unit and an underlying ophiolitic unit an associated ductile shear zone nearly 2000 m thick developed in the lower part of the hangingwall unit where the corredoiras orthogneiss a lower ordovician metagranite was progressively transformed into augengneisses mylonitic and ultramylonitic gneisses the attitude of the stretching and mineral lineation in the mylonites varies due to late refolding at map scale but the sense of movement can be estimated being roughly top to the se according to crosscutting relationships the cd developed subsequent to the thrusting of the high pressure high temperature unit onto the ophiolitic unit and prior to younger extensional detachments upright folding and strike slip tectonics the geometric relationships of the cd with the previous structures in the footwall unit the subtractive character of the metamorphic gap between its hangingwall and footwall and the available isotopic data suggest that the cd is an early variscan ductile extensional detachment the movement of which was roughly simultaneous with the onset of thrusting of the allochthonous complexes over their relative autochthon

is an ionospheric electron enhancement preceding the 2011 tohoku oki earthquake a precursor 1 heki 2011 reported that the tec gradually enhanced from 40 minutes before the 2011 m9 0 off the pacific coast of tohoku earthquake tohoku eq to the time when the co seismic acoustic wave reached the ionosphere and the tec immediately recovered at the normal state this paper shows an alternative interpretation of total electron content tec variation in the ionosphere associated with the tohoku eq our interpretation is that a tsunamigenic ionospheric hole a wide depletion of the tec occurred after the co seismic acoustic wave reached the ionosphere and gradually recovered at the normal state with several tens of minutes kakinami et al 2012 the difference between heki 2011 and kakinami et al 2012 is attributed to the reference curves of the tec to extract the ionospheric variations the former is given by the least squares fitting curve of the eq day data excluding an expected precursor period while the latter is given by the data of the similar orbit of global positioning system gps satellite on another day the results suggest that variation of slant tec is explained by the depletion of tec due to tsunami rather than the precursory enhancement

ionospheric anomalies possibly associated with m 6 0 earthquakes in the japan area during 1998 2010 case studies and statistical study abstract in this paper we examine pre earthquake ionospheric anomalies in time series and perform a statistical test by using total electron content tec derived from global ionosphere maps gim around the japan area for the first time the normalized gim tec gim tec which is computed based on 15 days backward running mean of gim tec have been investigated for minimizing possible confounding effects of consecutive earthquakes and identify the abnormal signals meanwhile to reduce the effect of strong geomagnetic activities such as geomagnetic storms the criterion for removing the gim tec data have been adapted that is when dst index exceeds 60 nt temporal variations of gim tec for large and destructive earthquakes in japan have been studied which are the 2004 mid niigata prefecture earthquake m6 8 its aftershock m6 1 the 2007 offshore mid niigata earthquake m6 8 and the 2008 iwate miyagi nairiku earthquake m7 2 although there are some positive and negative tec anomalies before and after the four earthquakes there is a tendency that positive tec anomalies appear 1 5 days before all the above earthquakes even during the quiet geomagnetic condition superposed epoch analyses have been performed for the statistical analysis of tec anomalies associated with m 6 0 earthquakes during the 12 year period of may 1998 may 2010 the statistical result indicates the significance of the positive tec anomalies 1 5 days before earthquakes within 1000 km from the epicenter around japan