long period pulses in broadband records of near earthquakes broadband records of weak local earthquakes occasionally exhibit long period pulselike signals appearing exclusively on horizontal components such signals have been recorded at station sergoula in the corinth gulf by guralp cmg 3t 100 sec and wielandt streckeisen sts 2 120 sec instruments the pulses can be perfectly matched by the instrumental responses to a small step of acceleration similar pulses observed during moderate near earthquakes at stations of the greek national network equipped with lennartz le 3d 20s 20 sec sensors can be explained in the same way numerical simulation of the pulses allows their removal thus making the records fully utilizable for waveform inversion in seismic source studies prerequisite for that is precise knowledge of the instrument transfer function we found that poles and zeros of the cmg 3t and sts 2 sensors were consistent with those given by the manufacturer whereas those of the le 3d 20s were not we identified the latter by inversion of spontaneous pulses incidentally appearing in le 3d 20s records without relation to any earthquake what actually generates the earthquake related horizontal acceleration steps remains unclear rapid and permanently lasting tilt is a very likely candidate when we numerically model a coseismic near field static displacement we actually find a tilt step but its amplitude is several orders below the observed values we therefore rather speculate that it is a very local tilt triggered by high frequency ground vibrations

erratum to observation and prediction of dynamic ground strains tilts and torsions caused by the mw 6 0 2004 parkfield california earthquake and aftershocks derived from upsar array observations online material corrected figures and strain rotation and displacement gradient time series

very high rate 10 hz gps seismology for moderate magnitude earthquakes the case of themw6 3 l aquila central italy event accepted for publication in journal of geophysical research copyright 2010 american geophysical union

archean crustal evolution of the west african craton example of the amsaga area reguibat rise upb and smnd evidence for crustal growth and recycling abstract new geochronological data u pb and sm nd are used to constrain the archean crustal growth and evolution of the southwestern part of the reguibat rise amsaga area in the west african craton the results are summarized as follows 1 u pb zircon data indicate an emplacement age of 2986 8 ma for the magmatic protolith of a charnockitic pluton in agreement with a whole rock sm nd isochron at 3012 142 ma positive nd 3 0 values ranging between 0 89 and 1 95 and agreement between nd model ages between 3 23 and 3 10 ga and u pb age indicate a juvenile origin for the magmatic protolith and imply a crustal growth event at ca 3 0 ga seven rims of the charnockitic zircons yield discordant 207 pb 206 pb ages ranging from 2979 11 to 2737 11 ma and are interpreted as resulting from growth during the granulitic event 2 whole rock sm nd data on migmatitic orthogneisses that form the central part of the area indicate an archean age for their magmatic protolith t dm ranging from 3 24 to 2 87 ga in agreement with a previous single zircon evaporation age of 2836 16 ma potrel 1994 3 two late tectonic postgranulite plutons both granite and gabbro dated at ca 2 73 ga mark the end of the granulitic event the granite provides a u pb age of 2726 7 ma and the gabbro a mineral sm nd isochron age of 2706 54 ma the t dm ages ranging from 3 1 to 3 2 ga indicate an origin by crustal reworking of the granite and negative nd 2 7 value 0 7 of the gabbro indicate crustal contamination during emplacement these results combined with previous work potrel et al 1996 indicate that the archean reguibat rise formed through a succession of crustal growth events from at least 3 50 3 45 ga until 2 73 ga a major granulitic event took place at ca 2 73 ga and was accompanied by emplacement of crustally derived magmas

magnetic fabrics and microstructures of the post collisional aegirine augite syenite triunfo pluton northeast brazil abstract anisotropy of magnetic susceptibility ams and microstructures of the neoproterozoic triunfo alkaline pluton situated in northeast brazil have been investigated in order to characterize fabrics formed during its emplacement bulk magnetic susceptibility in the pluton varies between 0 15 10 3 and 25 10 t 3 si and the mean magnetic anisotropy ratio is around 1 04 aegirine augite and secondary magnetite are the main carriers of the magnetic susceptibility with the former controlling the directions of the anisotropy magnetic foliation and lineation are consistently oriented throughout the pluton foliation typically dips gently to the northeast and lineation plunges gently to the east these structures were mostly acquired at the magmatic and sub magmatic stages the shape of the magnetic ellipsoid is dominantly oblate a feature that may reflect either the uniaxial oblate ams ellipsoid of the aegirine augite crystals and or a vertical compaction of the magma in its final stages of crystallization the foliation pattern suggests the pluton has a tabular shape within the basement rocks magma emplacement is inferred to have occurred by its lateral migration along a flat lying crustal structure after fracture propagation and ascension of the magma from a lower crust mantle source late fine grained vertical dykes with the same mineral composition as the triunfo syenite cross cut the wall rocks of the pluton and close the alkaline magmatism in the area the ne trending alignment of alkaline plutons and the nne trending syenitic dykes indicate that the emplacement of such bodies occurred along a crustal extension event with a minimum compressive stress horizontal trending roughly e w

post seismic relaxation following the 2009 april 6 l aquila italy earthquake revealed by the mass position of a broad band seismometer summary post seismic relaxation is known to occur after large or moderate earthquakes on time scales ranging from days to years or even decades in general long term deformation following seismic events has been detected by means of standard geodetic measurements although seismic instruments are only used to estimate short timescale transient processes albeit inertial seismic sensors are also sensitive to rotation around their sensitive axes the recording of very slow inclination of the ground surface at their standard output channels is practically impossible because of their design characteristics however modern force balance broad band seismometers provide the possibility to detect and measure slow surface inclination through the analysis of the mass position signal this output channel represents the integral of the broad band velocity and is generally considered only for state of health diagnostics in fact the analysis of mass position data recorded at the time of the 2009 april 6 l aquila mw 6 3 earthquake by a closely located sts 2 seismometer evidenced the occurrence of a very low frequency signal starting right at the time of the seismic event this waveform is only visible on the horizontal components and is not related to the usual drift coupled with the temperature changes this analysis suggests that the observed signal is to be ascribed to slowly developing ground inclination at the station site caused by post seismic relaxation following the main shock the observed tilt reached 1 7 10 5 rad in about 2 months this estimate is in very good agreement with the geodetic observations giving comparable tilt magnitude and direction at the same site this study represents the first seismic analysis ever for the mass position signal suggesting useful applications for usually neglected data

ductile duplexing at a bend of a continental scale strike slip shear zone example from ne brazil abstract during the pan african orogeny the borborema province in ne brazil developed a continental scale shear zone system that comprises ne and ew trending ductile strike slip shear zones remote sensing and structural mapping has revealed a pattern of arcuate anastomosing strike slip shear zones separating sigmoidal lenses of less deformed material located at the western end of the ew trending patos shear zone which is one of the largest shear zones of the province this structure of imbricate shear zones was initiated under high temperature deformation conditions it is interpreted as a ductile strike slip duplex and may represent a kinematic pattern for strain accommodation in response to a bend of a ductile mega shear zone

observation and prediction of dynamic ground strains tilts and torsions caused by the mw 6 0 2004 parkfield california earthquake and aftershocks derived from upsar array observationsdynamic ground strains tilts and torsions caused by the 2004 parkfield california earthquake

broadband sensor nonlinearity during moderate shaking abstract we observe that broadband seismometers may produce artifact long period signals that resemble impulse responses similar to a step in acceleration in the presence of shaking as moderate as 0 2 g this observation accords with recent observations in europe and elsewhere with similar instruments e g zahradnik and plesinger 2005 we present two case studies for both the 8 october 2006 m 4 5 earthquake near mt rainier in the pacific northwest and an m 5 0 event on 29 september 2004 in southern california artifact signals possible step tilts and apparent sensor problems are observed as far as about 200 km from the epicenters such long period artifacts if not recognized complicate and degrade estimation of source parameters of moderate and larger earthquakes on regional networks the exact cause of the artifacts currently remains obscure but may require alterations to instrument installation and or design strategies

tilts in strong ground motion most instruments used in seismological practice to record ground mo tion are pendulum seismographs velocigraphs or accelerographs in most cases it is assumed that seismic instruments are only sensitive to the translational motion of the instrument s base in this study the full equation of pendulum motion including the inputs of rotations and tilts is considered it is shown that tilting the accelerograph s base can severely impact its response to the ground motion the method of tilt evaluation using uncorrected strong motion accelerograms was first suggested by graizer 1989 and later tested in several laboratory experiments with different strong motion instruments the method is based on the difference in the tilt sensi tivity of the horizontal and vertical pendulums the method was applied to many of the strongest records of the mw 6 7 northridge earthquake of 1994 examples are shown when relatively large tilts of up to a few degrees occurred during strong earthquake ground motion residual tilt extracted from the strong motion record at the pacoima dam upper left abutment reached 3 1 in n45e direction and was a result of local earthquake induced tilting due to high amplitude shaking this value is in agreement with the residual tilt measured by using electronic level a few days after the earthquake the method was applied to the building records from the north ridge earthquake according to the estimates residual tilt reached 2 6 on the ground floor of the 12 story hotel in ventura processing of most of the strongest records of the northridge earthquake shows that tilts if happened were within the error of the method or less than about 0 5

pan african displaced terranes in the tuareg shield central sahara concepts developed in the recently published model of the air region eastern tuareg shield niger africa as a college of three displaced terranes integrated in a single geodynamic model lead us to propose a terrane map of the tuareg shield 500000 km 2 the 23 terranes recognized have their own lithological metamorphic magmatic and tectonic characteristics and are separated by subvertical strike slip megashear zones that can be traced for hundreds of kilometres or by major thrust fronts some of these boundaries have ophiolitic assemblages or molassic deposits the tuareg shield was shaped and partly accreted during the pan african orogeny 750 550 ma but not as a homogeneous body

the potassic granites of the igbeti area further evidence of the polycyclic evolution of the pan african belt in southwestern nigeria abstract field geochemical and isotopic studies on granitic rocks in the igbeti area of southwestern nigeria indicate that this pan african belt was affected by two episodes of granite plutonism represented by an older augen gneiss and a younger relatively undeformed coarse grained porphyritic granite these rocks have similar major element characteristics but their trace element compositions are sufficiently different to warrant a suggestion that they are probably of different origin rb sr whole rock isotopic analysis give an eburnean age of 1904 18 ma for the augen gneisses and a pan african age of 617 37 ma for the coarse grained porphyritic granite a low initial 87 sr 86 sr ratio 0 7005 0 0025 for the augen gneiss suggests derivation from the mantle or a low rb sr source whereas a value of 0 7120 0 0016 for the coarse grained porphyritic granite indicates a significantly older crustal component in the magma alkaline magmatism may have been an important component of orogenic magmatism during the eburnean event

tilt motions recorded at two wise sites for the 2003 tokachi oki earthquake m 8 3 abstract broadband velocity seismographs installed at the ohtsu water level observatory and monsizu stations of the warning information system of earthquake wise network recorded long period pulses produced by tilt motions resulting from the 2003 tokachi oki earthquake m 8 3 of 25 september 2003 the long period pulse signal is represented using a low pass filtered expansion composed of intrinsic mode functions by eliminating the leading phases such as a direct p phase that appears before the onset of tilt motion from the expansion the transient signal produced by the tilt motion is approximately obtained a reverse filter which is defined by the inverse of the frequency characteristics of the broadband velocity seismometer for the acceleration input is applied to the transient signal to estimate the tilt motion the estimated permanent acceleration of tilt motion at the two sites ranges from 0 6 to 6 5 cm sec 2 the river embankment adjacent to the ohtsu water level observatory site collapsed due to liquefaction at the bottom of the embankment the monsizu site was constructed at a depth of 2 m in soft soil floodplain deposits these two broadband velocity seismograms involving the tilt motion reveal that the tilt motion is mainly generated under the influence of the collapsed soil structure or of the deformation of the soil deposits these observations indicate that the broadband velocity seismograph is more sensitive to tilt motion than acceleration type strong motion seismographs

petrogenesis of juvenile type birimian paleoproterozoic granitoids in central cote d ivoire west africa geochemistry and geochronology abstract the birimian paleoproterozoic granitoids of central cote d ivoire are associated either with greenstone belts or with basin sedimentary rocks field data indicate two stages of granitoid emplacement which according to singlezircon and monazite 207 pb 206 pb age determinations occurred within a short period of time the first generation of granitoids 2123 2108 ma intruded and metamorphosed the greenstone belts whereas the second generation 2108 2097 ma intruded and metamorphosed the sedimentary pile and subordinate andesitic volcanic rocks of the bandama basin unconformably overlying the greenstone belts geochemical and isotopic data show that the various granitoids belong to four magmatic groups 1 sodic calc alkaline nacg 2 potassic calc alkaline kcg 3 peraluminous alg and 4 alkaline alkg all the granitoids show juvenile features with mantle like low initial sr isotopic compositions 0 700 0 702 and positive epsilon nd values 1 5 2 7 these data indicate that a the nacg may have formed by partial melting of a garnet amphibolite crust b the kcg and alkg derived from partial melting of crustal mafic to intermediate metaigneous rocks and c the alg epsilon nd 1 5 represent infracrustal melting of young sialic igneous materials during a regional crustal shortening in a transcurrent tectonic context sm nd model ages 2 25 2 4 ga preclude the existence of an archean crust reworked in the birimian magmas an underplating model is discussed

ground rotational motions of the 1999 chi chi taiwan earthquake as inferred from dense array observations 1 large rotational motions excited by the 1999 chi chi taiwan earthquake are inferred from a dense acceleration array near the northern end of the rupture fault where large surface slips along the fault are observed the estimated major frequency content is from 0 1 to 1 0 hz with a peak near 0 2 hz it is found that in the footwall region the observed strong rotational ground motions were most probably excited by the slip of the northern rupture ending segment of the chi chi earthquake fault and that its thrust slips induced a major rock motion in the radial component the analysis here indicates that during the chi chi earthquake significant rotation seismic energy was radiated from the bent northern end of the earthquake fault further analysis of rotational ground motions may provide useful constraints for its rupture mechanisms

estimating small permanent rotation from strong motion records what is comparison with external measurements telling us abstract modern strong motion accelerometers record instruments translational accelerations as well as their rotation based on a detailed analysis of the low frequency content of acceleration records javelaud et al 2011 removed the permanent tilt information from strong motion records the accuracy of permanent rotation angles derived from acceleration time histories can be checked by comparison with external rotation information in practice this can be done at exceptional sites that experience earthquake induced permanent rotation and where the permanent rotation is recorded by various instruments situated above a hidden fault and located 4 km from the epicenter during the 2000 m j 7 3 western tottori earthquake in japan kasho dam experienced very strong shaking and a homogeneous tectonic rotation of about 1 5 10 4 rad over the dam and its reservoir areas because the dam is well instrumented plumb line strong motion seismometers pre and post earthquake ground surveys it makes an ideal site to check the accuracy of tectonic permanent rotation estimated from records of the strong motion seismometer located at the dam s foundation as a result of this benchmark the permanent rotation obtained from the analysis of strong motion acceleration time histories is consistent with external measurements which validates the methodology used and that strong motion time histories can be used to estimate permanent rotation

tilt effects on moment tensor inversion in the near field of active volcanoes dynamic tilts rotational motion around horizontal axes change the projection of local gravity onto the horizontal components of seismometers this causes sensitivity of these components to tilt especially at low frequencies we analyse the consequences of this effect onto moment tensor inversion for very long period vlp events in the near field of active volcanoes on the basis of synthetic examples using the station distribution of a real deployed seismic network and the topography of mt merapi volcano java indonesia the examples show that for periods in the vlp range of 10 30 s tilt can have a strong effect on the moment tensor inversion although its effect on the horizontal seismograms is significant only for few stations we show that tilts can be accurately computed using the spectral element method and include them in the green s functions the simulated tilts might be largely influenced by strain tilt coupling stc however due to the frequency dependence of the tilt contribution to the horizontal seismograms only the largest tilt signals affect the source inversion in the vlp frequency range as these are less sensitive to stc than the weaker signals the effect of stc can likely be neglected in this application in the converse argument this is not necessarily true for longer periods where the horizontal seismograms are dominated by the tilt signal and rotational sensors would be necessary to account for it as these are not yet commercially available this study underlines the necessity for the development of such instruments

strain tilt and rotation associated with strong ground motion in the vicinity of earthquake faults abstract in the absence of near field records of differential ground motion induced by earthquakes we simulate the time histories of strain tilt and rotation in the vicinity of earthquake faults embedded in layered media we consider the case of both strike slip and dip slip fault models and study the effect of different crustal structures the maximum rotational motion produced by a buried 30 km long strike slip fault with slip of 1 m is of the order of 3 10 4 rad while the corresponding rotational velocity is about 1 5 10 3 rad sec a simulation of the san fernando earthquake yields maximum longitudinal strain and tilt a few kilometers from the fault of the order of 8 10 4 and 7 10 4 rad these values being small compared to the amplitude of ground displacement the results suggest that most of the damage occurring in earthquakes is caused by translation motions we also show that strain and tilt are closely related to ground velocity and that the phase velocities associated with strong ground motions are controlled by the rupture velocity and the basement rock shearwave velocity

a quantitative approach for estimating coseismic displacements in the near field from strong motion accelerographs the translational accelerations recorded by strong motion seismometers are often contaminated by baseline offsets that prevent recovering theground displace ments by double integration detailed analysis of the k net95 strong motion seis mometer and the improvement of the visual display of the recorded accelerations fourier transform by addition of long zero pads to the acceleration records made it possible to distinguish the origins of the long period noise that contaminate the translational accelerations recorded in the near field of two studied earthquakes the 2004 niigata ken chuetsu earthquake and the 2007 niigata ken chuetsu oki earthquake japan they are the residual rotation of the instrument residual tilt or the 1 f digital semiconductor noise the quantification of these two terms allows us to discuss the low frequency content of the records and to describe when it is possible to obtain realistic displacement time histories it happens when the residual tilt is removed in the time domain or when the 1 f semiconductor noise overshadows the translational acceleration records up to sufficiently small frequencies as a check of the method displacement time histories obtained from acceleration records are compared with nearby 1 hz gps data good similitudes are obtained in the near field for collocated instruments online material figures showing acceleration velocity and displacement time series and acceleration spectra for 18 records

coastal cliff ground motions from local ocean swell and infragravity waves in southern california 1 ground motions atop a southern california usa coastal cliff are compared with water level fluctuations observed at the cliff base and with ground motions observed 10 km inland at high tide cliff top ground motions in three frequency bands were generated locally by ocean waves at the cliff base 1 high frequency 0 3 hz shaking caused by waves impacting the cliff and 2 gravitational loading induced swaying at the frequency of the incident sea swell waves 0 05 0 1 hz and 3 slow swaying at infragravity frequencies 0 006 0 05 hz at high tide at infragravity and incident sea swell wave frequencies cliff top vertical ground displacement and cliff base water level fluctuations are coherent and oscillate in phase with occasional deviation at sea swell frequencies and spectral levels at the cliff top are much higher than at the inland seismometer in contrast at double frequencies 0 1 0 3 hz spectral levels of vertical motions are nearly identical inland and at the cliff top consistent with a common distant or spatially distributed source at low tide when ocean waves did not reach the cliff base power levels of vertical ground motions at the cliff top decreased to inland levels at incident wave frequencies and higher and only infragravity band motions were noticeably forced by local ocean waves

ground deformation cycles in a magma effusive stage and sub plinian and vulcanian eruptions at kirishima volcanoes japan 1 the dynamics of explosive eruptions such as plinian sub plinian vulcanian and strombolian ones is one of the most fascinating subjects in volcano physics during the early period of volcanic activity at the shinmoe dake volcano in 2011 various kinds of activities such as sub plinian eruptions a magma effusion and vulcanian eruptions occurred sequentially a different kind of tilt motion accompanied each activity here we clarify the characteristics of the tilt motions and their time sequences presenting a new explanation of the triggering mechanism of a vulcanian eruption the sub plinian and the vulcanian eruptions at the shinmoe dake volcano were preceded by inflations at shallow depths near the summit the inflation deflation cycles were also recorded during the magma effusive stage with a typical period of 1 h synchronized with volcanic tremors or long period events almost all vulcanian eruptions were preceded by trapezoidal inflations whose durations systematically lengthened as time progressed and were followed by various time sequences of tilt motions which became increasingly more complicated throughout the frequent vulcanian eruptions we have found clear linearity with a constant gradient of 0 45 between the logarithm of the preceding duration versus elapsed time for each substage these observations can be consistently explained based on the assumption that a vulcanian eruption is induced by a catastrophic rupture of the strongest closed solid magma frame due to magma degassing overpressure and the degassing from magma declines exponentially with time

late proterozoic arc continent and continent continent collision in the pan african trans saharan belt of mali the tilemsi magmatic arc preserved along the suture zone of the pan african trans saharan belt of northern mali crops out as a series of northeast to north northeast trending strips along the tilemsi mesozoic trough and is about 100 km in width the volcanic arc series includes pillowed metabasalts of tholeiitic character and associated with rhyodacites overlying sedimentary rocks are turbiditic volcanic greywackes they are progressively recrystallized into grey gneiss in the vicinity of gabbro noritic and dioritic intrusions u pb zircon dating of a crosscutting metaquartz diorite gives a nearly concordant age of while that of a plagiogranite mobilizate associated with the grey gneiss is initial nd and sr isotopic compositions of two metaquartz diorites end730 6 6 6 3 87sr 86sr i 0 7024 are in a agreement with a depleted mantle source similar to modern intraoceanic arcs isotopic compositions of two tilemsi metagreywackes end730 5 8 4 3 87sr 86sr 0 7027 exclude any significa

confirmation of the double asperity model for the 2016 mw 6 6 akto earthquake nw china by seismic and insar data abstract on november 25 2016 an mw 6 6 earthquake struck akto a county in the xinjiang autonomous region of china this earthquake nucleated on the dextral steep dip strike slip segment of the muji fault in the western tibetan plateau in this study we conducted a joint inversion using a higher number of data than in previous works i e teleseismic p and sh waveform near field seismic waveform and coseismic insar displacement data in order to analyze the spatiotemporal rupture process of this seismic event the results of the joint inversion showed that the event consisted in a primarily unilateral rupture toward east southeast along the muji fault and that 90 of the scalar seismic moment was released in the first 18 s moreover we confirmed the occurrence of two major asperities the first one located right next to the hypocenter and the second one 30 35 km east of the hypocenter the first asperity was found at a deeper depth than the second asperity additionally it was larger and had a smaller slip the results of the coulomb stress change analysis suggested that the rupture of the first asperity triggered the rupture of the second one the heterogeneity of the on fault slip revealed the heterogeneity of the inherent strength and stress of the muji fault moreover the clear slip deficit area characterized by a high coulomb stress might indicate a high seismic risk

metamorphic zircons from north cameroon implications for the pan african evolution of central africa morphoscopic studies of zircons including optical microscopic and sem backscattered electron mode from the roniers valley west poli northern cameroon indicate an important crystallization of zircon during a medium grade garnet kyanite metamorphic event this was associated with a deformation d1 and with the emplacement of a basic and intermediate plutonic suite bip u pb dating of these zircon gave almost concordant pan african ages 630 ma which contribute to a solution of a major regional uncertainty about the age of the regional d1 event which in the mobile belt of central africa has been considered previously either as pan african or as lower to middle proterozoic a chronological framework is proposed for the evolution of northern cameroon

processes of soft sediment clast formation in the intertidal zone abstract muddy soft sediment clasts found on the sandy beach at formby point north west england are formed by wave erosion of late holocene intertidal sediments that are exposed during summertime ridge and runnel development break up processes of the intertidal sediments are strongly controlled by pre existing bedding and surface desiccation cracks erosion of the intertidal sediments and formation of soft sediment clasts contributes to the provision of fines into this dominantly sandy environment but loss of the archaeologically significant holocene intertidal sediments is a potentially important management issue along this coast

very long period conduit oscillations induced by rockfalls at kilauea volcano hawaii 1 eruptive activity at the summit of kilauea volcano hawaii beginning in 2010 and continuing to the present time is characterized by transient outgassing bursts accompanied by very long period vlp seismic signals triggered by rockfalls from the vent walls impacting a lava lake in a pit within the halemaumau pit crater we use raw data recorded with an 11 station broadband network to model the source mechanism of signals accompanying two large rockfalls on 29 august 2012 and two smaller average rockfalls obtained by stacking over all events with similar waveforms to improve the signal to noise ratio to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous medium that takes topography into account we apply a new waveform inversion method that accounts for the contributions from both translation and tilt in horizontal seismograms through the use of green s functions representing the seismometer response to translation and tilt ground motions this method enables a robust description of the source mechanism over the period range 1 1000 s the vlp signals associated with the rockfalls originate in a source region 1 km below the eastern perimeter of the halemaumau pit crater the observed waveforms are well explained by a simple volumetric source with geometry composed of two intersecting cracks including an east striking crack dike dipping 80 to the north intersecting a north striking crack another dike dipping 65 to the east each rockfall is marked by a similar step like inflation trailed by decaying oscillations of the volumetric source attributed to the efficient coupling at the source centroid location of the pressure and momentum changes induced by the rock mass impacting the top of the lava column assuming a simple lumped parameter representation of the shallow magmatic system the observed pressure and volume variations can be modeled with the following attributes rockfall volume 200 4500 m3 length of magma column 120 210 m diameter of pipe connecting the halemaumau pit crater to the subjacent dike system 6 m average thickness of the two underlying dikes 3 6 m and effective magma viscosity 30 210 pa s most rockfalls occur during episodes of sustained deflation of the kilauea summit the mass loss rate in the shallow magmatic system is estimated to be 1400 15 000 kg s 1 based on measurements of the temporal variation of vlp period in the two large rockfalls that occurred on 29 august 2012

armored mud balls from cabretta and sapelo barrier islands georgia abstract armored mud balls similar to ones previously studied on marine and lacustrine shorelines are now forming on sapelo and cabretta islands georgia this report constitutes the first study of armored mud ball formation in a harrier island environment small 0 3 1 5 m high sea cliffs of pleistocene marsh deposits in the lower foreshore erode to form the mud ball cores during transport to the upper foreshore beach sediment partially armors the surface of the mud cores predominance of sand size armor and rootbound cores set these samples apart from earlier studies intermittent rolling in the swash zone on the gently sloping beach flattens the core and concentrates armor on opposing sides no evenly armored very highly spherical mud halls common to fluvial environments were found in his study area because several armored mud balls were found buried in sand on the backshore it is likely that some will be preserved such lithified armored mud balls may be especially useful in determining seaward facies of ancient barrier island deposits

proterozoic history of the borborema province ne brazil correlations with neighboring cratons and pan african belts and implications for the evolution of western gondwana 1 geological and geochronological correlations between borborema province ne brazil and neighboring cratons and brasiliano pan african belts indicate that the amazonian west african and sao francisco congo cratons and the basement of the araguaia borborema nigerian and cameroon provinces were part of the atlantica supercontinent this continent was established at the end of the transamazonian eburnean cycle 2 0 ga and apart from ubiquitous taphrogenesis in the 1 8 1 7 ga interval remained largely unaffected for the following 1 ga around 1 ga an important magmatic event in borborema province correlates with rifting episodes and anorogenic magmatism in the sao francisco congo and amazonian cratons these events are interpreted as failed attempts to break up atlantica which at this time may have been part of the larger rodinia supercontinent renewed extensional conditions in borborema province during the middle and late neoproterozoic are attributed to far field stresses transmitted to the interior of atlantica by outwardly dipping subduction zones that encircled its northern present day coordinates portion the rarity of petrotectonic assemblages typical of subduction zone environments indicates that extension did not evolve enough to form large oceans basins and thus that the borborema province essentially includes reworked intracontinental domains regional deformation and metamorphism starting at 650 640 ma and shear zone development beginning at 590 595 ma were continuously developed through time and were synchronous throughout most of the borborema araguaia cameroon and nigerian provinces postorogenic conditions were reached 540 530 myr ago while active deformation was still occurring in other belts that accreted around atlantica to form western gondwana

are microseismic ground displacements a significant geomorphic agent this paper considers the role that microseismic ground displacements may play in fracturing rock via cyclic loading and subcritical crack growth using a coastal rock cliff as a case study we firstly undertake a literature review to define the spatial locations that may be prone to microseismic damage it is suggested that microseismic weakening of rock can only occur in damage accumulation zones of limited spatial extent stress concentrations resulting from cliff height slope angle and surface morphology may nucleate and propagate a sufficiently dense population of microcracks that can then be exploited by microseismic cyclic loading we subsequently examine a 32 day microseismic dataset obtained from a coastal cliff top location at staithes uk the dataset demonstrates that microseismic ground displacements display low peak amplitudes that are punctuated by periods of greater displacement during storm conditions microseismic displacements generally display limited preferential directivity though we observe rarely occurring sustained ground motions with a cliff normal component during storm events high magnitude displacements and infrequently experienced ground motion directions may be more damaging than the more frequently occurring reduced magnitude displacements characteristic of periods of relative quiescence as high magnitude low frequency events exceed and then increase the damage threshold these extremes may also render intervening reduced magnitude microseismic displacements ineffective in terms of damage accumulation as a result of crack tip blunting and the generation of residual compressive stresses that close microcracks we contend that damage resulting from microseismic ground motion may be episodic rather than being continuous and in quasi proportional and cumulative response to environmental forcing a conceptual model is proposed that describes when and where microseismic ground motions can operate effectively we hypothesise that there are significant spatial and temporal limitations on effective microseismic damage accumulation such that the net efficacy of microseismic ground motions in preparing rock for fracture and hence in enhancing erosion may be considerably lower than previously suggested in locations where high magnitude displacements punctuate standard displacement conditions determining and measuring the exact effects of microseismic ground displacement on damage accumulation and as a trigger to macro scale fracture in the field is not currently possible though our model remains consistent with field observations and conceptual models of controls on rockfall activity

the effects of seismic rotations on inertial sensors summary with the important increase in the number of instruments especially in the near field of quite significant earthquakes unsaturated traces have led seismologists to question what they are really measuring we have performed a review of previous studies related to the effects of rotations on both horizontal and vertical components of various sensors illustrations of near field records show that the recovering static displacement requires an accurate rotation estimation that present day seismometers cannot achieve estimations of coseismic tilts rotation around an horizontal axis using seismometers cannot be achieved independently of translational motion therefore for specific configurations such as near field or long period far field reconstruction of the ground motion requires specific rotation measurements effects of the chi chi earthquake 1999 on accelerograms make the static displacement estimation unreliable for long period background noise far field horizontal seismic signals present unexpected n45 polarization which is explained by the similar influence of the rotation around the vertical axis on the two horizontal components for the geoscope network this feature has been seen for stations with a streckeisen sts 1 sensor while those with a streckeisen sts 2 sensor do not show this polarization feature this study suggests that sensor installation should follow a protocol that will better guarantee the verticality of the sensors moreover rotational recordings with ad hoc sensors are necessary and by adequately correcting the traces they will enable us to reconstruct the translational motion from recorded seismic signals

tilt change recorded by broadband seismometer prior to small phreatic explosion of meakan dake volcano hokkaido japan 1 we discovered an anomalous very long period vlp signal duration about 60 s in the broadband seismic record of the precursory swarm of a small phreatic explosion at the meakan dake volcano hokkaido japan in 2006 this signal was masked by a short period tremor in the original velocity waveform but a considerable dc step appeared in the displacement trace since such a step results from a tilt change we interpreted the observed trace as being a combination of rotational tilt and translational displacement motions the apparent displacement step in the vlp signal indicates subsidence of the summit crater owing to limited data we attempted deflating the mogi source and simulating the seismic record including both motions when only rotational motion is considered the simulated waveform explains well the general features of the observed trace however the combined trace has incompatible phases suggesting that a more complicated source process should be considered

strain transfer at continental scale from a transcurrent shear zone to a transpressional fold belt the patos serido system northeastern brazil during the brasiliano pan african orogeny a complex continental scale pattern of east west transcurrent shear zones and northeast trending fold belts formed in the northern and central borborema province of northeastern brazil the east west shear zones have been usually regarded as slightly younger features but the study of the most spectacular case of intersection between these two structures the patos shear zone and the serido transpressional belt leads to a different tectonic model satellite imagery and structural petro logical and geophysical data support the interpretation that these structures 1 are in structural continuity and 2 formed simultaneously under amphibolite facies metamorphic conditions that led to partial melting this suggests a model of strain transfer at the scale of the orogen at the eastern end of the patos east west dextral shear zone the strain that accommodated the relative motion of the northern block was transferred to the northeast trending serido belt where it resulted in folding strike slip faulting and stretching parallel to the strike of the belt

beaches and beach related facies holocene barrier islands of georgia the mesotidal coast of georgia encompasses diverse sedimentary features and depositional environments most of which typify major facies of the entire georgia bight a broad embayment on the southeastern u s shelf barrier island strandline environments especially include tidal inlets and shoals the beach shoreface foreshore and backshore and dunes and washover fans low energy beach segments may grade directly into small seaside tidal flats relict salt marsh deposits crop out on erosional beaches all deposits are in dynamic equilibrium with fluctuating coastal conditions and a gradual rise in sea level most of these facies are important in interpreting ancient epeiric transgressive regressive coastal sequences pronounced local variations in the overall sequence result from complex latero vertical relationships between 1 the shoreface foreshore and shoals and 2 the shoals low energy beaches and beach related tidal flats washover fans and relict deposits on erosional beaches cause perturbations within present day lateral relationships but are normal in transgressive facies tracts along such coasts close stratigraphic control of outcrops or cores would be necessary for detailed reconstructions of or correlations among ancient analogs

large scale silicate liquid immiscibility a possible example from northeastern brazil abstract ultrapotassic peralkalic silica saturated plutons 580 ma are widespread in the cachoeirinha salgueiro foldbelt northeastern brazil they consist of alkali feldspar syenites with pyroxenite as co magmatic inclusions and syn plutonic or late stage dikes pyroxenite and syenite have the same mineral phases aegirine augite microcline sphene apatite blue amphibole magnetite but only in different proportions rare inclusions of a mixed rock about 60 syenite 40 pyroxenite in an emulsion like texture are also present pyroxenes in the three units are all only slightly zoned silica saturated and extremely low in al2o3 0 2 1 4 amphiboles are mostly k rich richterite characterized by high sio2 low al2o3 and tio2 contents and low mg the three rock types have similar ree chondrite normalized patterns with negative slopes and lack of eu anomaly with the total ree in the pyroxenite greater than that of the syenite trace element patterns for the mixed rock are intermediate between those for the pyroxenite and syenite major element partitioning between pyroxenite and syenite has the same sense as that one observed between immiscible liquids in volcanic lavas and trace element partitioning is similar to the experimentally determined partition of immiscible liquid pairs the rocks have similar high 18o values avg w r 8 smow corrected from pyroxene high initial 87 sr 86 sr ratios about 0 710 and low 143 nd 144 nd avg 0 51104 field and geochemical characteristics indicate chemical equilibrium among the three rock types and suggest liquid immiscibility between syenite and pyroxenite the mixed rock representing the original magma composition

cross shore decay of cliff top ground motions driven by local ocean swell and infragravity waves 1 ground motions at the frequencies between 0 01 and 0 1 hz of ocean infragravity and swell waves were observed on a cross shore transect extending landward from the edge of a southern california coastal cliff cliff top ground motions are coherent and in phase with water level fluctuations at the cliff base vertical ground motions at infragravity and single frequencies decay rapidly with inland distance from the cliff edge e folding scale is about 12 m and at the edge decrease by several orders of magnitude between high tide when waves reach the cliff base and low tide when the waterline is about 50 m from the cliff base the observed cross shore decay scales are qualitatively consistent with gravitational loading and attraction of water waves at tidally modulated distances from the cliff base at approximately constant distance from the waterline ground motions vary roughly linearly with nearshore swell wave energy in contrast to these locally forced ground motions double frequency band 0 1 0 2 hz cliff top vertical ground motions are remotely generated with spatially uniform magnitudes approximately equal to those observed 14 km inland near the cliff edge ground tilt dominates the observed large relative to vertical cross shore acceleration at infragravity frequencies contributes significantly to cross shore acceleration at swell frequencies and is a small fraction of cross shore acceleration at higher frequencies

seismic source dynamics of gas piston activity at kilauea volcano hawai i since 2008 eruptive activity at the summit of kilauea volcano hawai i has been confined to the new overlook pit crater within the halema uma u crater among the broad range of magmatic processes observed in the new pit are recurring episodes of gas pistoning the gas piston activity is accompanied by seismic signals that are recorded by a broadband network deployed in the summit caldera we use raw data recorded with this network to model the source mechanism of representative gas piston events in a sequence that occurred on 20 25 august 2011 during a gentle inflation of the kilauea summit to determine the source centroid location and source mechanism we minimize the residual error between data and synthetics calculated by the finite difference method for a point source embedded in a homogeneous medium that takes topography into account we apply a new waveform inversion method that accounts for the contributions from both translation and tilt in horizontal seismograms through the use of green s functions representing the seismometer response to translation and tilt ground motions this method enables a robust description of the source mechanism over the period range 1 10 000 s most of the seismic wavefield produced by gas pistoning originates in a source region 1 km below the eastern perimeter of the halema uma u pit crater the observed waveforms are well explained by a simple volumetric source with geometry composed of two intersecting cracks featuring an east striking crack dike dipping 80 to the north intersecting a north striking crack another dike dipping 65 to the east each gas piston event is marked by a similar rapid inflation lasting a few minutes trailed by a slower deflation ramp extending up to 15 min attributed to the efficient coupling at the source centroid location of the pressure and momentum changes accompanying the growth and collapse of a layer of foam at the top of the lava column assuming a simple lumped parameter representation of the shallow magmatic system the observed pressure and volume variations can be modeled with the following attributes foam thickness 10 50 m foam cell diameter 0 04 0 10 m and gas injection velocity 0 01 0 06 m s 1 gas piston activity occurs in a narrow pipe with diameter of 6 m connecting the halema uma u pit crater to the subjacent dike system the height of the magma column is estimated at 104 m at the start of the sequence based on the period of very long period vlp oscillations accompanying the onset of the gas piston signal based on the change in the period of vlp oscillations and tilt evidence the height of the magma column is inferred to have risen by up to 23 m by the end of the 5 day long sequence a penny shaped crack model of the dike geometry yields effective diameters of 1 2 2 9 km for the east dike and 0 7 km for the north dike the shallower north dike segment is embedded in a relatively weak medium compatible with expected mechanical properties in the hydrothermal environment of this dike

thermal history of the pan african brasiliano borborema province of northeast brazil deduced from 40ar 39ar analysis abstract detailed step heating 40 ar 39 ar analyses were performed on different minerals from magmatic and metamorphic rocks of the borborema province this region located in northeast brazil belongs to the pan african brasiliano belt which is about 1000 km wide and 600 km long twenty six single grains of amphibole muscovite and biotite were extracted from eighteen samples selected in an area of about 17 500 km 2 250 km by 70 km in the patos region this region has been affected by a continental scale shear zone system well defined 40 ar 39 ar plateau ages and an u pb analysis on zircon leterrier j jardim de sa e f bertrand j m and pin c 1994 ages u pb sur zircon de granitoides brasilianos de la ceinture du serido province borborema ne bresil c r acad sci paris 318 1505 1511 allow the definition of a homogeneous and unusual slow cooling history 3 4 c ma and suggest a rather slow uplift rate between 580 and 500 ma followed by a fast cooling of the whole studied area around 500 ma rapid cooling is suggested by concordant plateau ages on muscovite and biotite the existence of such an event at the end of the belt history is in agreement with data obtained on other major belts such as the alpine himalayan system or the hercynian belt

crustal evolution of the pernambuco alagoas complex borborema province ne brazil nd isotopic data from neoproterozoic granitoids the borborema province in northeast brazil forms the western part of a major 600 ma brasiliano pan african mobile belt that extends from brazil through central africa in a pre drift reconstruction of gondwanaland the pernambuco alagoas peal complex is a large area within the borborema province and consists of high grade migmatitic gneisses and granitic batholiths although the peal complex has previously been called a massif or terrane in reality it comprises many different types of protoliths or plutons the protoliths for many of the migmatitic gneisses are difficult to decipher due to the varied deformation and metamorphism during the cariris velhos and brasiliano orogenies nd isotopic data discriminate two major crustal domains in the peal complex the garanhuns and the agua branca domains rocks of the garanhuns domain have nd tdm in the range of 1 8 to 2 4 ga indicating that most of it is underlain by paleoproterozoic crust and does not include significant mesoproterozoic or neoproterozoic crustal additions the marimbondo correntes batholith is inside the garanhuns domain but includes younger tdm ages similar to those found in the agua branca domain this batholith includes contributions from younger sources and may intrude a block of younger allocthonous crust thrust over the older crust of the garanhuns domain rocks of the agua branca domain show tdm within the range of 0 90 to 2 10 ga with most nd model ages between 1 5 and 1 0 ga the pre brasiliano crust in this domain thus includes substantial amounts of mesoproterozoic to neoproterozoic additions the presence of some older model ages suggests that the aguas belas domain may have some vertical crustal zonation with paleoproterozoic and neoproterozoic crustal segments tectonically interleaved during successive accretional or collisional episodes including the ultimate brasiliano collision at 600 ma the mesoproterozoic nd model ages therefore represent mixing of different crustal and mantle sources rather than a discrete episode of mesoproterozoic crustal formation various metaluminous or peraluminous granitoids of brasiliano age from the buique paulo afonso aguas belas caninde and marimbondo correntes batholiths show tdm ranging from 0 90 ga to 1 10 ga suggesting that they either were wholly derived from juvenile material of the 1 0 ga cariris velhos orogeny or contain substantial contributions of juvenile material from the 0 6 ga brasiliano cycle some high k to shoshonitic granitoids from the aguas belas domain show mesoproterozoic 1 4 ga tdm model ages the model ages recorded in these plutons could suggest either that the magma was derived from enriched lithospheric mantle associated with the cariris velhos orogeny or that it was a mixture between enriched lower crust of transamazonian age and juvenile material from the cariris velhos or brasiliano orogenies

ground rotational motions recorded in near source region of earthquakes large rotational motions excited by earthquakes are recorded during an earthquake swarm of march 1997 offshore ito in izu peninsula japan the largest rotational velocity recorded at kaw is 2 6 10 2 rad s around the north south axis during an earthquake of magnitude 5 2 at 14 09 gmt on march 3 the rotational motions around the vertical axis excited by the largest event is 3 3 10 3 rad s considering a spatial variation of slip velocity which directly relates to excitation of a rotational motion we apply a simple point source model to the largest event and succeed in explaining the observed rotational motion around the vertical axis

on baseline corrections and uncertainty in response spectrafor baseline variations commonly encounteredin digital accelerograph records most digital accelerograph recordings are plagued by long period drifts best seen in the velocity and displacement time series obtained from integration of the acceleration time series these drifts often result in velocity values that are nonzero near the end of the record this is clearly unphysical and can lead to inaccurate es timates of peak ground displacement and long period spectral response the source of the long period noise seems to bevariations in the acceleration baseline in many cases these variations could be due to true ground motion tilting and rotation as well as local permanent ground deformation instrumental effects or analog to digital con version very often the trends in velocity are well approximated by a linear trend after the strong shaking subsides the linearity of the trend in velocity implies that no vari ations in the baseline could have occurred after the onset of linearity in the velocity time series this observation combined with the lack of any trends in the pre event motion allows us to compute the time interval in which any baseline variations could occur we then use several models of the variations in a monte carlo procedure to derive a suite of baseline corrected accelerations for each noise model using records from the 1999 chi chi earthquake and several earthquakes in turkey comparisons of the mean values of the peak ground displacements spectral displacements and resid ual displacements computed from these corrected accelerations for the different noise models can be used as a guide to the accuracy of the baseline corrections for many of the records considered here the mean values are similar for each noise model giving confidence in the estimation of the mean values the dispersion of the ground motion measures increases with period and is noise model dependent the dispersion of in elastic spectra is greater than the elastic spectra at short periods but approaches that of the elastic spectra at longer periods the elastic spectra from the most basic proces sing in which only the pre event mean is removed from the acceleration time series do not diverge from the baseline corrected spectra until periods of 10 20 sec or more for the records studied here implying that for many engineering purposes elastic spec tra can be used from records with no baseline correction or filtering

obliquely convergent tectonics and granite emplacement in the trans saharan belt of eastern nigeria a synthesis abstract the eastern nigeria terrane belongs to the 3000 km long trans saharan belt which was formed in the neoproterozoic between 750 and 500 ma by continental collision between the converging west african craton congo craton and east saharan block the study area consists mostly of gneisses and migmatites that underwent granulite facies metamorphism 800 c 800 mpa in contrast with western nigeria and cameroon no basement cover relationship has been identified which is in agreement with a monocyclic metamorphic history around 640 ma the area underwent a nappe tectonics with eastward displacement emplacement of bt ms granites and granulite facies peak later on around 615 ma nappes were towards the north numerous hbl bt granite plutons were emplaced around 585 ma during north south strike slip regional deformation the anisotropy of magnetic susceptibility fabric helps in defining strain localization along narrow north south to nne ssw vertical shear zones during the exhumation history exhumation of the terrane assessed using u pb ar ar and rb sr methods was presumably slow with uplift rates around 0 2 0 5 mm year preliminary estimates of contemporaneous horizontal movements suggest that they were one order of magnitude larger

morphology and palaeoenvironmental interpretation of deformed soft sediment clasts examples from within late pleistocene glacial outwash tempo valley northern ireland abstract glacial outwash deposited during deglaciation of the late devensian ice sheet is present as a flat topped valley fill in the tempo valley on the southern flanks of the fintona hills northern ireland sedimentologically the outwash comprises well sorted and interbedded rippled to massive sands which record distal deposition within a proglacial water body beds of ripple drift cross laminated sands contain deformed folded and contorted soft sediment clasts which are composed mainly of silt and clay the soft sediment clasts were deformed prior to final deposition because clast a b planes lie conformable to sand laminae which are undeformed morphological characteristics of the soft sediment clasts and their facies context provide evidence for transport mechanisms depositional environment and processes of clast deformation the soft sediment clasts were transported into a proglacial water body by unidirectional water currents 1 5 2 5 m s 1 sediment transport processes include sediment bypassing within the water column a low bedload component and grain flow activity during waning flow stages the overall morphology of soft sediment clasts records between 1 and 3 distinct phases of hydroplastic deformation prior to emplacement the deformation phases are recognised on the basis of morphologically unrolling the superimposed folds of the soft sediment clasts deformation structures i e fold style and direction of the principal stress axis relative to clast axes suggest that clasts were reoriented with respect to water flow direction following each deformation phase processes of deformation include folding over of the clast along its b axis into two or more components crumpling and abrasion of the outer margins of the b plane and squashing of the clast c axis some of which may be post depositional deformation the presence of silt and clay rich soft sediment clasts within the outwash succession suggests that they were ripped up from shallow and irregular pools on the glacier forefield into which fine sediments accumulated after flood or meltwater events and transported distally into a proglacial water body these inferences based on facies evidence and styles of hydroplastic deformation impact on reconstructions of local palaeogeography and the wider interpretation of similar soft sediment clasts in the geological record

effect of baseline corrections on displacements and response spectra for several recordings of the 1999 chi chi taiwan earthquake displacements derived from many of the accelerogram recordings of the 1999 chi chi taiwan earthquake show drifts when only a simple baseline de rived from the pre event portion of the record is removed from the records the appearance of the velocity and displacement records suggests that changes in the zero level of the acceleration are responsible for these drifts the source of the shifts in zero level are unknown but in at least one case it is almost certainly due to tilting of the ground this article illustrates the effect on the ground velocity ground dis placement and response spectra of several schemes for accounting for these baseline shifts a wide range of final displacements can be obtained for various choices of baseline correction and comparison with nearby gps stations none of which are colocated with the accelerograph stations do not help in choosing the appropriate baseline correction the results suggest that final displacements estimated from the records should be used with caution the most important conclusion for earthquake engineering purposes however is that the response spectra for periods less than about 20 sec are usually unaffected by the baseline correction although limited to the analysis of only a small number of recordings the results may have more general significance both for the many other recordings of this earthquake and for data that will be obtained in the future from similar high quality accelerograph networks now being installed or soon to be installed in many parts of the world

ultra long period seismic signals and cyclic deflation coincident with eruptions at santiaguito volcano guatemala abstract broadband seismic observations made near the active vent at santiaguito provide constraints on changing pressures inside the edifice during january 2009 we recorded episodic ultra long period signals ulps 30 s that were coincident with eruptive activity centered on the active el caliente vent these signals lasted 2 5 min and corresponded to depressurization of a volume beneath the dome coincident shorter period seismic signals 0 5 hz appeared to be associated with shallow level pyroclastic emissions and dome surface motions these shorter period signals varied significantly from event to event unlike the ulp waveforms which were self similar as opposed to the short period signals which were recorded across the network the ulps were only recorded on the horizontal channels of 3 stations that were within 1 1 km of the vent this and other factors suggest that they were a result of long period rotational motion rather than horizontal translation ulp source locations derived from horizontal particle motions point to the northwestern part of el caliente 150 m from the vent axis the general locus of activity from 1967 until flank collapses in 1989 1990 we modeled the ulp signal as a mogi source and solved for three dimensional location and equivalent source strength through analysis of 78 events we identify a mean mogi source that is 200 m west of and 250 m beneath the centre of the vent with the peak volume changes accompanying eruptions ranging from 125 to 1825 m 3 these inferred volume losses coincide with the onset of gas venting and or explosive eruptions at the surface of caliente based upon these observations we develop a model to describe the pre eruptive eruptive and inter eruptive physical processes occurring at the surface and inside santiaguito

recovering coseismic point ground tilts from collocated high rate gps and accelerometers 1 rotational along with translational and strain measurements are essential for a complete description of the motion of a deformable body in a seismic event we propose a new seismogeodetic approach where collocated high rate gps and accelerometer measurements are combined to estimate permanent and dynamic coseismic ground tilts at a point whereas at present only dynamic tilts are measured with either a dense seismic array or an expensive ring laser gyroscope we estimate point tilts for a five story structure on a shake table subjected to 13 earthquake strong motion records of increasing intensity for the most intense record from the 2002 m7 9 denali earthquake we observe a peak to peak dynamic tilt of 0 12 and a permanent tilt of 0 16 for the structure s roof point tilts derived from networks of collocated gps and accelerometers can be used to estimate the rotational component of the seismic wavefield for improved earthquake source characterization

very long period pulses at asama volcano central japan inferred from dense seismic observations summary we observed seismic events consisting of several one sided velocity pulses with durations of 5 30 s hereafter called very long period or vlp pulses using up to 14 broad band seismometers installed near the summit area of asama volcano japan particle motions do not point to a single source location despite their rectilinearities suggesting a non isotropic source mechanism together with path effect we conducted moment tensor inversion analyses for these events using the green s functions of not only translational motions but also of tilt motions the best fitting source locations are located north of the crater centre at depths of 100 150 m below the crater bottom the principal value ratios of moment tensor solutions can be approximated as 5 3 2 which is indicative of a combination of a tensile crack and a cylinder with the strike and dip angle of the crack both being nearly 70 and symmetry axis of the cylinder being inclined by nearly 30 from the vertical the time histories of moment tensors are indicative of an initial sudden pressurization and subsequent gradual depressurization at the source region we sought to model vlp pulses at asama volcano by considering the inflow and outflow of gas at the source cavity compensated by boiling in another deeper reservoir

generation transport and preservation of armoured mudballs in an ephemeral gully system abstract armoured mudballs have been reported from modern fluvial catchments and preserved in ancient quaternary and older sedimentary sequences despite many descriptions of mudballs in the literature there is little systematic analysis of their physical properties genesis transport and deposition within alluvial sequences this study uses two adjacent catchments developed on identical geology in southeast spain that offer a unique opportunity to examine the key controls on armoured mudball development as one catchment produces armoured mudball whilst the second does not field survey using a total station together with laboratory tests for material composition and aggregate stability were used to examine the catchment and the armoured mudballs the results show that the generation of the armoured mudballs is heavily dependent on the correct sediment supply suitable aggregates to act as mudball seeds and suitable fragments to source the armour and good slope channel coupling within the catchment coupling is facilitated by steep gully sides which deliver the weathered blocks of marl mudball seeds to the gully floor the seeds form the core of the mudballs in the mudball factory zone if the seeds are subjected to sealing by moisture from rainfall the mudball will hold together through negative pore pressures and can be transported by the ensuing gully flow as the mudball rolls it picks up a surface armour which becomes embedded into the mudball with longer transport paths the turbulent nature of the flow creates spherical mudballs which are size sorted downstream by the hydraulics of the flow rather than attrition armoured mudball deposition occurs within unit braid bars in areas of waning flow due to transmission losses within vegetated point or mid channel bars the armoured mudballs are preferentially deposited within the coarser bar head of these depositional units with smaller marl fragments forming the finer bar tail trenching of the bars reveals that the armoured mudballs are preserved in the subsurface although they may become increasingly flattened upon burial at depth and may be difficult to recognise due to disaggregation by roots this study suggests that armoured mudballs recognised in ancient alluvial sequences imply seasonality of climate and good slope channel coupling within the catchment area and that they are capable of transporting delicate flora undamaged making them good targets for pollen recovery in ancient alluvial sequences where armoured mudballs were present but go unrecognised in the ancient record the mode and energy of transportation and deposition of the fine sediment may be misinterpreted as the fines are in fact being transported as bedload rather than suspended load the armoured mudballs have also been noted to transport pristine microfauna such as ostracod shells from the source area material this may provide challenges to palaeoenvironmental interpretations of the mud dominated unit as environmentally significant fauna may not be contemporaneous with the unit

armoured and unarmoured till balls from the greenland sea floor two cores recovered in the greenland sea contain aggregates up to 5 cm in diameter of poorly sorted coarse grained material their lithologic and biogenic content in addition to the grain size and grain shape indicate that they are related to till balls it is possible that they formed in a fluvial or nearshore environment perhaps in greenland or siberia were frozen into fast ice and were then transported by sea ice rafting to their present location since the balls were still partly frozen they could survive the 2000 m drop through the water column to the seafloor