zonal and vertical structure of the madden julian oscillation abstract a statistical study of the three dimensional structure of the madden julian oscillation mjo is carried out by projecting dynamical fields from reanalysis and radiosonde data onto space time filtered outgoing longwave radiation olr data mjo convection is generally preceded by low level convergence and upward motion in the lower troposphere while subsidence cooling and drying prevail aloft this leads to moistening of the boundary layer and the development of shallow convection followed by a gradual and then more rapid lofting of moisture into the middle troposphere at the onset of deep convection after the passage of the heaviest rainfall a westerly wind burst region is accompanied by stratiform precipitation where lower tropospheric subsidence and drying coincide with continuing upper tropospheric upward motion the evolution of the heating field leads to a temperature structure that favors the growth of the mjo the analysis also reveals distinct differences in the vertical structure

fine structure of the landers fault zone segmentation and the rupture process observations and modeling of 3 to 6 hertz seismic shear waves trapped within the fault zone of the 1992 landers earthquake series allow the fine structure and continuity of the zone to be evaluated the fault to a depth of at least 12 kilometers is marked by a zone 100 to 200 meters wide where shear velocity is reduced by 30 to 50 percent this zone forms a seismic waveguide that extends along the southern 30 kilometers of the landers rupture surface and ends at the fault bend about 18 kilometers north of the main shock epicenter another fault plane waveguide disconnected from the first exists along the northern rupture surface these observations in conjunction with surface slip detailed seismicity patterns and the progression of rupture along the fault suggest that several simple rupture planes were involved in the landers earthquake and that the inferred rupture front hesitated or slowed at the location where the rupture jumped from one to the next plane reduction in rupture velocity can tentatively be attributed to fault plane complexity and variations in moment release can be attributed to variations in available energy

propagating diurnal disturbances embedded in the madden julian oscillation 1 fine structure of large scale intraseasonal disturbance associated with the madden julian oscillation mjo was analyzed using the 3 hourly 3b42 trmm rainfall data over the maritime continent diurnal cycle becomes pronounced during the passage of mjo and the eastward propagating diurnal disturbances pdds dominate as an internal structure of large scale convection system of mjo importantly fast pdds that penetrate through the islands are observed within the slowly propagating mjo system this eastward penetration of pdds through the islands result in a sudden shift of the convection center from the western part of the islands to the east causing an overall propagation of the mjo from the indian ocean to the pacific our results demonstrate that the diurnal cycle of convection over and around the major islands thus plays an active role in the propagation of the mjo over the maritime continent

high resolution imaging of the bear valley section of the san andreas fault at seismogenic depths with fault zone head waves and relocated seismicity summary detailed imaging of fault zone fz material properties at seismogenic depths is a difficult seismological problem owing to the short length scales of the structural features seismic energy trapped within a low velocity damage zone has been utilized to image the fault core at shallow depths but these phases appear to lack sensitivity to structure in the depth range where earthquakes nucleate major faults that juxtapose rocks of significantly different elastic properties generate a related phase termed a fault zone head wave fzhw that spends the majority of its path refracting along the fault we utilize data from a dense temporary array of seismometers in the bear valley region of the san andreas fault to demonstrate that head waves have sensitivity to fz structure throughout the seismogenic zone measured differential arrival times between the head waves and direct p arrivals and waveform modelling of these phases provide high resolution information on the velocity contrast across the fault the obtained values document along strike fault normal and downdip variations in the strength of the velocity contrast ranging from 20 to 50 per cent depending on the regions being averaged by the ray paths the complexity of the fz waveforms increases dramatically in a region of the fault that has two active strands producing two separate bands of seismicity synthetic waveform calculations indicate that geological observations of the thickness and rock type of the layer between the two strands are valid also for the subsurface structure of the fault the results show that joint analysis of fzhws and direct p arrivals can resolve important smallscale elements of the fz structure at seismogenic depths detailed characterization of material contrasts across faults and their relation to earthquake ruptures is necessary for evaluating theoretical predictions of the effects that these structures have on rupture propagation

winter monsoon convection in the vicinity of north borneo part i structure and time variation of the clouds and precipitation abstract radar and satellite observations in the vicinity of northern borneo obtained during the international winter monsoon experiment wmonex showed that the convection in that region underwent an extremely regular diurnal cycle over the sea to the north of borneo the general level of convective activity was increased during monsoon surges and during the passages of westward propagating near equatorial disturbances convective activity was decreased during monsoon lulls the diurnal cycle was well defined regardless of whether the general level of convective activity was enhanced or suppressed by synoptic scale events the cycle of convection over the sea was especially well documented it was typically initiated at about midnight when an offshore low level wind began where this wind met the monsoonal northeasterly flow usually just off the coast convective cells formed after midnight the convection continued to develop and by 0800 lst it had evolved into an organized mesoscale system with a

a shallow fault zone structure illuminated by trapped waves in the karadere duzce branch of the north anatolian fault western turkey summary we discuss the subsurface structure of the karadere duzce branch of the north anatolian fault based on analysis of a large seismic data set recorded by a local passcal network in the 6 months following the mw 7 4 1999 izmit earthquake seismograms observed at stations located in the immediate vicinity of the rupture zone show motion amplification and long period oscillations in both p and s wave trains that do not exist in nearby off fault stations examination of thousands of waveforms reveals that these characteristics are commonly generated by events that are well outside the fault zone the anomalous features in fault zone seismograms produced by events not necessarily in the fault may be referred to generally as fault zone related site effects the oscillatory shear wave trains after the direct s arrival in these seismograms are analysed as trapped waves propagating in a low velocity fault zone layer the time difference between the s arrival and trapped waves group does not grow systematically with increasing source receiver separation along the fault these observations imply that the trapping of seismic energy in the karadere duzce rupture zone is generated by a shallow fault zone layer traveltime analysis and synthetic waveform modelling indicate that the depth of the trapping structure is approximately 3 4 km the synthetic waveform modelling indicates further that the shallow trapping structure has effective waveguide properties consisting of thickness of the order of 100 m a velocity decrease relative to the surrounding rock of approximately 50 per cent and an s wave quality factor of 10 15 the results are supported by large 2 d and 3 d parameter space studies and are compatible with recent analyses of trapped waves in a number of other faults and rupture zones the inferred shallow trapping structure is likely to be a common structural element of fault zones and may correspond to the top part of a flower type structure the motion amplification associated with fault zone related site effects increases the seismic shaking hazard near fault zone structures the effect may be significant since the volume of sources capable of generating motion amplification in shallow trapping structures is large

diurnally modulated cumulus moistening in the preonset stage of the madden julian oscillation during dynamo abstractatmospheric soundings radar and air sea flux measurements collected during dynamics of the madden julian oscillation dynamo are employed to study mjo convective onset i e the transition from shallow to deep convection in the tropical indian ocean the findings indicate that moistening of the low midtroposphere during the preonset stage of the mjo is achieved by simultaneous changes in the convective cloud population and large scale circulation namely cumuliform clouds deepen and grow in areal coverage as the drying by large scale subsidence and horizontal westerly advection wane the reduction of large scale subsidence is tied to the reduction of column radiative cooling during the preonset stage which ultimately links back to the evolving cloud population while net column moistening in the preonset stage is tied to large scale circulation changes a new finding of this study is the high degree to which the locally driven diurnal cycle invigorates convective clouds and cumulus moiste

observation of a quasi 2 day wave during toga coare abstract detailed structure of the quasi 2 day oscillation observed in the active phase of the madden julian oscillations during the intensive observation period of tropical ocean and global atmosphere coupled ocean atmosphere response experiment toga coare iop was described a variety of observational platforms is used including high resolution gms infrared histogram rain rate estimate from toga and mit radar measurements upper air soundings and boundary layer profiler winds from the integrated sounding system and surface data from the imet buoy the quasi 2 day mode had a westward propagation speed of 12 15 day 1 a horizontal wavelength of 25 30 longitude a coupling with the westward propagating n 1 inertio gravity waves was hypothesized from the space time power spectral distribution of the cloud field the wind disturbance structure was consistent with the hypothesis the vertical wave structure had an eastward phase tilt with height below 175 hpa and vice versa above indicating the wav

the diurnal cycle of precipitation over the maritime continent in a high resolution atmospheric model climate models can exhibit systematic errors in their mean precipitation over the maritime continent of the indonesian archipelago at the heart of the tropical warm pool these can often be traced back to an erroneous simulation of the diurnal cycle and can lead to errors in global climate through planetary wave propagation here we examine the simulation of the diurnal cycle over the maritime continent in a series of high resolution integrations of the uk met office atmospheric model with horizontal resolutions of 40 and 12 km where the convection is parametrised and 4 km where the convection is explicitly resolved as part of the cascade project in these models the vertical heating profile over the islands changes from a convective profile with a mid tropospheric maximum in the early afternoon to a more stratiform profile with upper tropospheric heating and mid tropospheric cooling later the convective heating profile forces a first internal mode gravity wave that propagates rapidly offshore the deep warm anomalies behind its downwelling wavefront suppress convection offshore during early afternoon the stratiform heating profile forces a gravity wave with a higher order vertical mode that propagates slowly offshore later in the afternoon this mode has a negative destabilising temperature anomaly in the mid troposphere together with the convergence zone between the wave fronts of the two modes favourable conditions are created for offshore convection in the 4 km explicit convection model the offshore convection responds strongly to this gravity wave forcing in agreement with observations supporting a gravity wave convection paradigm for the diurnal cycle over the maritime continent however the convective response in the lower resolution models is much less coherent leading to errors in the diurnal cycle and mean precipitation hence to improve climate model simulations sensitivity to gravity wave forcing should be a factor in future convective parametrisation schemes copyright c 2011 royal meteorological society

numerical simulation of fault zone guided waves accuracy and 3 d effects fault zones are thought to consist of regions with reduced seismic velocity when sources are located in or close to these low velocity zones guided seismic head and trapped waves are generated which may be indicative of the structure of fault zones at depth observations above several fault zones suggest that they are common features of near fault radiation yet their interpretation may be highly ambiguous analytical methods have been developed to calculate synthetic seismograms for sources in fault zones as well as at the material discontinuities these solutions can be used for accurate modeling of wave propagation in plane parallel layered fault zone structures however at present it is not clear how modest deviations from such simplified geometries affect the generation efficiency and observations of trapped wave motion as more complicated models cannot be solved by analytical means numerical methods must be employed in this paper we discuss 3 d finite difference calculations of waves in modestly irregular fault zone structures we investigate the accuracy of the numerical solutions for sources at material interfaces and discuss some dominant effects of 3 d structures we also show that simple mathematical operations on 2 d solutions generated with line sources allow accurate modeling of 3 d wave propagation produced by point sources the discussed simulations indicate that structural discontinuities of the fault zone e g fault offsets larger than the fault zone width affect significantly the trapping efficiency while vertical properly gradients fault zone narrowing with depth small scale structures and moderate geometrical variations do not the results also show that sources located with appropriate orientations outside and below a shallow fault zone layer can produce considerable guided wave energy in the overlying fault zone layer

seismic and geodetic evidence for extensive long lived fault damage zones during earthquakes slip is often localized on preexisting faults but it is not well understood how the structure of crustal faults may contribute to slip localization and energetics growing evidence suggests that the crust along active faults undergoes anomalous strain and damage during large earthquakes seismic and geodetic data from the calico fault in the eastern california shear zone reveal a wide zone of reduced seismic velocities and effective elastic moduli using seismic traveltimes trapped waves and interferometric synthetic aperture radar observations we document seismic velocities reduced by 40 50 and shear moduli reduced by 65 compared to wall rock in a 1 5 km wide zone along the calico fault observed velocity reductions likely represent the cumulative mechanical damage from past earthquake ruptures no large earthquake has broken the calico fault in historic time implying that fault damage persists for hundreds or perhaps thousands of years these fi ndings indicate that faults can affect rock properties at substantial distances from primary fault slip surfaces and throughout much of the seismogenic zone a result with implications for the amount of energy expended during rupture to drive cracking and yielding of rock and development of fault systems

propagating and nonpropagating mjo events over maritime continent abstractthe observed outgoing longwave radiation olr and era interim data during 1979 2008 from november to april were analyzed to reveal fundamental differences between eastward propagating ep and nonpropagating np mjo events across the maritime continent mc it was found that when the maximum mjo convection arrives near 120 e a positive moisture tendency lies in a longitudinal zone 10 s 10 n 130 170 e for the ep cases whereas a negative tendency appears in the same region for the np cases in the latter cases there are clearly detectable westward propagating rossby wave type dry signals over the equatorial central western pacific the dry rossby wave signal may hinder the development of new convection to the east of the mjo convective center preventing the eastward propagation of the mjo a moisture budget analysis shows that the positive tendency of specific humidity in the ep composite is mainly attributed to the advection of the mean moisture by an intraseasonal ascending motion ano

properties of seismic fault zone waves and their utility for imaging low velocity structures a two dimensional solution for the scalar wave equation in a model of two vertical layers between two quarter spaces is used to study properties of seismic waves in a laterally heterogeneous low velocity structure the waves referred to as seismic fault zone waves include head waves internal fault zone reflections and trapped waves the analysis aims to clarify the dependency of the waves on media velocities media attenuation coefficients layer widths and source receiver geometry additional calculations with extreme low velocity layers provide examples that may be relevant for volcanic and geothermal domains the interference patterns controlling seismic fault zone waves change with the number of internal reflections in the low velocity structure this number increases with propagation distance along the structure decreases with fault zone width and increases for given length scales with the velocity contrast the relative lateral position of the source within the low velocity layer modifies die length scales associated with internal reflections and influences the resulting interference pattern low values of q affect considerably the dominant period and overall duration of the waves thus there are significant tradeoffs between propagation distance along the structure fault zone width velocity contrast source location within the fault zone and q the lateral and depth receiver coordinates determine the particular point where the interference pattern is sampled and observed motion is a strong function of both coordinates the zone connecting sources generating fault zone waves and observation points with appreciable wave amplitude can be over an order of magnitude larger than the fault zone width calculations for cases with layer p wave velocity of 200 m s 1 modeling a vertical dike or crack with fluid and gas show conspicuous persisting oscillations the results resemble aspects of seismic data in volcanic domains if these waves exist in observed records their explicit recognition and modeling will help to separate source and structural effects and aid in the interpretation of volcano seismology signals although the tradeoffs in parameters governing seismic fault zone waves are significant each variable has its own signature and the parameters may be constrained by additional geophysical data simultaneous modeling of many waveforms with an appropriate solution can resolve the various parameters and provide a high resolution structural image

multiple fault rupture of the m7 1 hector mine california earthquake from fault zone trapped waves 1 we studied the complex multiple faulting pattern of the 40 km long rupture zone of the 1999 m7 1 hector mine california earthquake with fault zone trapped waves generated by near surface explosions and aftershocks and recorded by linear seismic arrays deployed across the surface rupture the explosion excited trapped waves with relatively large amplitudes at 3 5 hz and a long duration of s coda waves are similar to those observed for aftershocks but have lower frequencies and travel more slowly three dimensional finite difference simulations of fault zone trapped waves indicate a 75 to 100 m wide low velocity and low q zone waveguide along the rupture surface on the lavic lake fault llf in the bullion mountains the s velocity within the waveguide varies from 1 0 to 2 5 km s at depths of 0 8 km reduced by 35 45 from the wall rock velocity and q is 10 60 the pattern of aftershocks for which we observed trapped waves shows that this low velocity waveguide has two branches in the northern and southern portions of the rupture zone indicating a multiple fault rupture at seismogenic depth north of the bullion mountains although only the rupture segment on the northwest llf broke to the surface a rupture segment on a buried fault also extended 15 km in the more northerly direction from the main shock epicenter to the south the rupture on the llf intersected the bullion fault bf and bifurcated the rupture on the south llf extended 10 km from the intersection and diminished while there was minor rupture on the southeast bf which dips to the northeast and disconnects from the llf at depth thus the analysis of fault zone trapped waves helps delineate a more complex set of rupture planes than the surface breakage in accord with the complex pattern of aftershock distribution and geodetic evidence that the hector mine event involved several faults which may also rupture individually our simulations of dynamic rupture using a finite element code show that generic models are able to produce the general features of the northern part of the rupture including slips on subparallel fault segments the models indicate that such a faulting pattern is physically plausible and consistent with observations

effect of dry large scale vertical motions on initial mjo convective onset anomalies of eastward propagating large scale vertical motion with 30 day variability at addu city maldives move into the indian ocean from the west and are implicated in madden julian oscillation mjo convective onset using ground based radar and large scale forcing data derived from a sounding array typical profiles of environmental heating moisture sink vertical motion moisture advection and eulerian moisture tendency are computed for periods prior to those during which deep convection is prevalent and those during which moderately deep cumulonimbi do not form into deep clouds convection with 3 7 km tops is ubiquitous but present in greater numbers when tropospheric moistening occurs below 600 hpa vertical eddy convergence of moisture in shallow to moderately deep clouds is likely responsible for moistening during a 3 7 day long transition period between suppressed and active mjo conditions although moistening via evaporation of cloud condensate detrained into the environment of such clouds may also be important reduction in large scale subsidence associated with a vertical velocity structure that travels with a dry eastward propagating zonal wavenumbers 1 1 5 structure in zonal wind drives a steepening of the lapse rate below 700 hpa which supports an increase in moderately deep moist convection as the moderately deep cumulonimbi moisten the lower troposphere more deep convection develops which itself moistens the upper troposphere reduction in large scale subsidence associated with the eastward propagating feature reinforces the upper tropospheric moistening helping to then rapidly make the environment conducive to formation of large stratiform precipitation regions whose heating is critical for mjo maintenance

winter monsoon convection in the vicinity of north borneo part ii effects on large scale fields abstract an observational study of the thermodynamic and kinematic structure and properties of monsoon convective systems and their large scale environment over the southern south china sea during the field phase december 1978 of the winter monsoon experiment wmonex has been carried out the primary observations used are from three soviet research vessels positioned in a triangular array off the north coast of borneo during the period 6 28 december computations of thermodynamic fields divergence and vertical motion have been made for the duration of the field phase based on six hourly rawinsonde releases at the ship sites analysis of the data indicates that the degree of convective activity over the southern south china sea is modulated by long period synoptic forcing monsoon surges easterly waves and also significantly by diurnal forcing land sea breeze circulations a diurnal cycle of convection persists in the region whether the synoptic scale forcing is weak or strong convection over wate

depth dependent structure of the landers fault zone from trapped waves generated by aftershocks we delineate the internal structure of the johnson valley and kickapoo faults landers southern rupture at seismogenic depth using fault zone trapped waves generated by aftershocks trapped waves recorded at the dense linear seismic arrays deployed across and along the surface breaks of the 1992 m7 5 landers earthquake show large amplitudes and dispersive wave trains following the s waves group velocities of trapped waves measured from multiple band pass filtered seismograms for aftershocks occurring at different depths between 1 8 km and 8 2 km show an increase in velocity with depth velocities range from 1 9 km s at 4 hz to 2 6 km s at 1 hz for shallow events while for deep events velocities range from 2 3 km s at 4 hz to 3 1 km s at 1 hz coda normalized amplitude spectra of trapped waves peak in amplitudes at 3 4 hz for stations located close to the fault trace the amplitude decays rapidly with the station offset from the fault zone normalized amplitudes also decrease with distance along the fault giving an apparent q of 30 for shallow events and 50 for deep events we evaluated depth dependent fault zone structure and its uncertainty from these measurements plus our previous results from near surface explosion excited trapped waves li et al 1999 in a systematic model parameter searching procedure using a three dimensional 3 d finite difference computer code graves 1996 our best model of the landers fault zone is 250 m wide at the surface tapering to 100 150 m at 8 2 km depth the shear velocity within the fault zone increases from 1 0 to 2 5 km s and q increases from 20 to 60 in this depth range fault zone shear velocities are reduced by 35 to 45 from those of the surrounding rock and also vary along the fault zone with an increase of 10 near ends of the southern rupture zone

fault zone trapped seismic waves two instances of fault zone trapped seismic waves have been observed at an active normal fault in crystalline rock near oroville in northern california trapped waves were excited with a surface source and recorded at five near fault borehole depths with an oriented three component borehole seismic sonde at parkfield california a borehole seismometer at middle mountain recorded at least two instances of the fundamental and first higher mode seismic waves of the san andreas fault zone at oroville recorded particle motions indicate the presence of both love and rayleigh normal modes the love wave dispersion relation derived for an idealized wave guide with velocity structure determined by body wave travel time inversion yields seismograms of the fundamental mode that are consistent with the observed love wave amplitude and frequency applying a similar velocity model to the parkfield observations we obtain a good fit to the trapped wavefield amplitude frequency dispersion and mode time separation for an asymmetric san andreas fault zone structure a high velocity half space to the southwest a low velocity fault zone a transition zone containing the borehole seismometer and an intermediate velocity half space to the northeast in the parkfield borehole seismic data set the locations depth and offset normal to fault plane of natural seismic events which do or do not excite trapped waves are roughly consistent with our model of the low velocity zone we conclude that it is feasible to obtain near surface borehole records of fault zone trapped waves because trapped modes are excited only by events close to the fault zone proper thereby fixing these events in space relative to the fault a wider investigation of possible trapped mode waveforms recorded by a borehole seismic network could lead to a much refined body wave tomographic velocity model of the fault and to a weighting of events as a function of offset from the fault plane it is an open question whether near surface sensors exist in a stable enough seismic environment to use trapped modes as an earth monitoring device

squall lines and convectively coupled gravity waves in the tropics why do most cloud systems propagate westward abstractthe coupling between tropical convection and zonally propagating gravity waves is assessed through fourier analysis of high resolution 3 hourly 0 5 satellite rainfall data results show the familiar enhancement in power along the dispersion curves of equatorially trapped inertia gravity waves with implied equivalent depths in the range 15 40 m i e pure gravity wave speeds in the range 12 20 m s 1 here such wave signals are seen to extend all the way down to zonal wavelengths of around 500 km and periods of around 8 h suggesting that convection wave coupling may be important even in the context of mesoscale squall lines this idea is supported by an objective wave tracking algorithm which shows that many previously studied squall lines in addition to 2 day waves can be classified as convectively coupled inertia gravity waves with the dispersion properties of shallow water gravity waves most of these disturbances propagate westward at speeds faster than the background flow to under

composition microstructures and petrophysics of the mozumi fault japan in situ analyses of fault zone properties and structure in sedimentary rocks from shallow crustal levels 1 we characterize the chemical microstructural and geophysical properties of fault related rock samples from the 80 100 m wide mozumi fault zone north central honshu japan the fault is exposed in a research tunnel 300 400 m below the ground and we combine geological data with borehole geophysical logs to determine the elastic and seismic properties of the fault zone detailed mapping within the tunnel reveals that the fault zone consists of two zones of breccia to foliated cataclasites 20 and 50 m thick two narrow tens of centimeters wide principal slip zones on which most of the slip occurred bound the central fault zone the dominant deformation mechanisms within the fault zone were brittle fracture brecciation slip localization plastic deformation and vein formation in a sericite calcite rich matrix clay alteration patterns are complex within the fault zone with clay rich fault breccia enriched in smectite illite and kaolinite relative to the kaolinite and illite dominant in the host rock whole rock geochemical analyses show that the fault related rocks are depleted in fe na k al mg and si relative to the host rock the fault zone exhibits depressed electrical resistivity values by 10 100 ohm m relative to the wall rock values of vp and vs values that are 0 30 and 0 40 km s 10 20 less than protolith values the spontaneous potential logs indicate that the fault zone has increased freshwater content relative to formation waters wellbore based measurements of vp and vs in fault related rocks to enable us to calculate values of young s modulus from 16 2 to 44 9 gpa and poisson s ratio for the fault zone of 0 263 to 0 393 the protolith has young s modulus of 55 4 gpa and a poisson s ratio of 0 242 lowest calculated values of young s modulus and highest calculated values of poisson s ratio correspond to fault breccia with increased porosity high fluid content and low resistivity values taken together these data show that the shallow portion of the mozumi fault consists of a complex zone of anastomosing narrow slip zones that bound broad zones of damage fluid rock alteration and deformation created altered fault related rocks which have resulted in overall reduced interval velocities of the fault zone these data indicate that seismic waves traveling along the interface or internally reflected in the fault zone would encounter rocks of differing and reduced elastic properties relative to the host rocks but that in detail material properties within the fault may vary

topographic effects on the tropical land and sea breeze abstractthe effect of an inland plateau on the tropical sea breeze is considered in terms of idealized numerical experiments with a particular emphasis on offshore effects the sea breeze is modeled as the response to an oscillating interior heat source over land the parameter space for the calculations is defined by a nondimensional wind speed a scaled plateau height and the nondimensional heating amplitude the experiments show that the inland plateau tends to significantly strengthen the land breeze part of the circulation as compared to the case without terrain the strengthening of the land breeze is tied to blocking of the sea breeze density current during the warm phase of the cycle the blocked sea breeze produces a pool of relatively cold stagnant air at the base of the plateau which in turn produces a stronger land breeze density current the following morning experiments show that the strength of the land breeze increases with the terrain height at least for moderate values of the height

horizontal polarization of ground motion in the hayward fault zone at fremont california dominant fault high angle polarization and fault induced cracks summary we investigate shear wave polarization in the hayward fault zone near niles canyon fremont ca waveforms of 12 earthquakes recorded by a seven accelerometer seismic array around the fault are analysed to clarify directional site effects in the fault damage zone the analysis is performed in the frequency domain through h v spectral ratios with horizontal components rotated from 0 to 180 and in the time domain using the eigenvectors and eigenvalues of the covariance matrix method employing three component records the near fault ground motion tends to be polarized in the horizontal plane at two on fault stations where the local strike is n160 ground motion polarization is oriented n88 19 and n83 32 respectively at a third on fault station the motion is more complex with horizontal polarization varying in different frequency bands however a polarization of n86 7 similar to the results at the other two on fault stations is found in the frequency band 6 8 hz the predominantly high angle polarization from the fault strike at the hayward fault is consistent with similar results at the parkfield section of the san andreas fault and the val d agri area a quaternary extensional basin in italy in all these cases comparisons of the observed polarization directions with models of fracture orientation based on the fault movement indicate that the dominant horizontal polarization is near orthogonal to the orientation of the expected predominant cracking direction the results help to develop improved connections between fault mechanics and near fault ground motion

thermodynamic and circulation characteristics of winter monsoon tropical mesoscale convection abstract during the december 1978 field phase of the international winter monsoon experiment winter monex a regular diurnal cycle of deep convective activity occurred over the south china sea immediately to the north of borneo the convection was initiated during the late night hours by convergence of the low level northeast monsoon flow with the land breeze along borneo s north coast the precipitation feature that developed was characterized during its mature stage by a nearly continuous stratiform cloud referred to here as a mesoscale anvil of 100 500 km dimension extending from the mid troposphere 5 km to near the tropopause 17 km using rawinsonde data from the sounding network thermodynamic and circulation characteristics of the convection are documented mesoscale upward motion is found to within the anvils with a mcsomc downdraft below producing a warm dry region over a lame area just above the boundary layer air flow relative to the anvil on both its leading and trailing edges i

discontinuity of the mozumi sukenobu fault low velocity zone central japan inferred from 3 d finite difference simulation of fault zone waves excited by explosive sources abstract we delineate shallow structures of the mozumi sukenobu fault central japan using fault zone waves generated by near surface explosions and detected by a seismometer array two explosive sources s1 and s2 were placed at a distance of about 2 km from the array and the other two s3 and s4 were at a distance of about 4 km fault zone head waves and fault zone trapped waves following direct p wave arrivals were clearly identified in the seismograms recorded by a linear seismometer array deployed across the fault in a research tunnel at a depth of 300 m synthetic waveforms generated by a 3 d finite difference 3 d fd method were compared with observed fault zone waves up to 25 hz the best fitting model indicates a 200 m wide low velocity zone extending at least to shot site s1 located 2 km east of the seismic array with a 20 decrease in the p wave velocity relative to the wall rock the width of the low velocity zone is consistent with the fault zone defined by direct geological observation in the research tunnel however the low velocity zone should disappear just to the east of the site s1 to explain the observed fault zone waves for shot s3 and s4 located 4 km east of the seismometer array yet the observation and the simulation show notable trapped wave excitation even though shots s3 and s4 are outside the fault zone these results indicate that 1 the effective waveguide for seismic waves along the fault does not exist east of source site s1 although the surface traces of the fault are observed in this region and 2 considerable trapped waves can be excited by sources well outside the fault zone these results highlight the along strike variability in fault zone structure

propagation of the madden julian oscillation through the maritime continent and scale interaction with the diurnal cycle of precipitation the convectively active part of the madden julian oscillation mjo propagates eastward through the warm pool from the indian ocean through the maritime continent the indonesian archipelago to the western pacific the maritime continent s complex topography means the exact nature of the mjo propagation through this region is unclear model simulations of the mjo are often poor over the region leading to local errors in latent heat release and global errors in medium range weather prediction and climate simulation using 14 northern winters of trmm satellite data it is shown that where the mean diurnal cycle of precipitation is strong 80 of the mjo precipitation signal in the maritime continent is accounted for by changes in the amplitude of the diurnal cycle additionally the relationship between outgoing long wave radiation olr and precipitation is weakened here such that olr is no longer a reliable proxy for precipitation the canonical view of the mjo as the smooth eastward propagation of a large scale precipitation envelope also breaks down over the islands of the maritime continent instead a vanguard of precipitation anomalies of 2 5 mm day 1 over 10 6 km 2 jumps ahead of the main body by approximately 6 days or 2000 km hence there can be enhanced precipitation over sumatra borneo or new guinea when the large scale mjo envelope over the surrounding ocean is one of suppressed precipitation this behaviour can be accommodated into existing mjo theories frictional and topographic moisture convergence and relatively clear skies ahead of the main convective envelope combine with the low thermal inertia of the islands to allow a rapid response in the diurnal cycle which rectifies onto the lower frequency mjo hence accurate representations of the diurnal cycle and its scale interaction appear to be necessary for models to simulate the mjo successfully

spatial variations in fault zone structure along the nojima fault central japan as inferred from borehole observations of fault zone trapped waves abstract we investigated the fault zone structures fault zone width shear wave velocity and q s of the nojima fault japan using the love wave type fault zone trapped waves ltws recorded at two borehole stations tos2 and hrb located along the fault tos2 depth 1673 m is located at an end of the fault while hrb depth 600 or 720 m is located in the middle section of the fault where the greatest surface displacement of 2 m was recorded during the 1995 kobe earthquake the distance between the two stations is about 4 km we found 22 records that exhibit typical ltw we assumed the fault zone structure to be a 2d uniform low velocity wave guide and estimated the averaged fault zone structure from the hypocenter to receiver by modeling the ltws because we can infer the low velocity fault zone to a depth of 8 km by observing the duration of ltws we obtain the average fault zone structure from the borehole stations to a depth of approximately 8 km the width shear wave velocity and q s of the fault zone beneath hrb are 100 m 2 9 km sec and 60 respectively on the other hand the average width of the fault zone beneath tos2 is 220 m which is larger than that beneath hrb we also conducted 3d finite difference modeling of ltws to confirm the spatial variations in the fault zone structure to a depth of 8 km the numerical simulation suggests that the nojima fault has uniform elastic and attenuation properties along the fault zone to a depth of 8 km while the width of the fault zone increases with the distance from the hrb to the south

diurnal patterns of rainfall in northwestern south america part i observations and context one of the rainiest areas on earth the panama bight and pacific western littoral of colombia is the focal point for a regional modeling study utilizing the fifth generation pennsylvania state university ncar mesoscale model mm5 with nested grids in this first of three parts the observed climatology of the region is presented the seasonal march of rainfall has a northwest southeast axis with western colombia near the center receiving rain throughout the year this study focuses on the august september season the diurnal cycle of rainfall over land exhibits an afternoon maximum over most of south and central america typically composed of relatively small convective cloud systems over some large valleys in the andes and over lake maracaibo a nocturnal maximum of rainfall is observed a strong night morning maximum of rainfall prevails over the coastal ocean propagating offshore and westward with time this offshore convection often takes the form of mesoscale convective systems with sizes comparable to the region s coastal concavities and other geographical features the 10 day period of these model studies 28 august 7 september 1998 is shown to be a period of unusually active weather but with a time mean rainfall pattern similar to longer term climatology it is concluded that the rain producing processes during this time period are likely to be typical of those that shape the seasonal climatology

a delineation of the nojima fault ruptured in the m7 2 kobe japan earthquake of 1995 using fault zone trapped waves we used four linear seismic arrays of portable seismometers at the northern awaji island japan to record fault zone trapped waves from aftershocks of the 1995 m7 2 hyogoken nanbu kobe earthquake from april to june 1996 three arrays were deployed across the nojima fault which ruptured during the mainshock while one array was deployed across the higashiura fault which did not break recently we observed significant fault zone trapped waves with relatively large amplitudes and the long wave train following s waves only when both the stations and aftershocks were located close to the nojima fault the coda normalized spectral amplitudes of trapped waves show a maximum peak at 4 7 hz which decreases rapidly with distance from the fault trace the normalized amplitudes of trapped waves also show a decrease with hypocentral distance along the fault giving an apparent q of approximately 25 at 4 7 hz in comparison the array across the higashiura fault recorded much shorter wave trains with higher frequencies after s arrivals for the same events we simulate these trapped waves as s waves guided in a low velocity waveguide sandwiched between high velocity wall rocks we find an adequate fit by using a waveguide 60 m wide at the northern site and 30 40 m wide elsewhere along the nojima fault a waveguide s velocity of 1 5 1 7 km s and a q value of 25 for the higashiura fault the s velocity is 2 5 km s and the q value is 80 the locations of aftershocks for which we observed fault zone trapped waves show that the nojima waveguide is 9 km long and dips southeastward at 80 85 to a depth of 16 km it extends 6 km farther south westward along the asano fault though there are no obvious surface breaks along it however the waveguide is disconnected from the suma fault on the main island which was also ruptured during the kobe earthquake possibly because of the existence of an offset between the nojima fault and the suma fault

observation of quasi 2 day convective disturbances in the equatorial indian ocean during dynamo abstractthis study examines the westward propagating convective disturbances with quasi 2 day intervals of occurrence identified over gan island in the central indian ocean from mid to late octobe

evolution of the population of precipitating convective systems over the equatorial indian ocean in active phases of the madden julian oscillation three dimensional radar reflectivity fields from a dual wavelength doppler polarimetric radar s polka deployed in the equatorialindian ocean are used to evaluate the composition of the populationof convective cloud elements during active phases of the mjo rainfall in active periods was intermittent occurring in 11 episodesofabout 2 4days separated byseveralnonrainydays dataforthese 2 dayperiodswerecomposited relative to the time of maximum rainfall analysis of the s polka data shows the makeup of the convective population during the rainfall episodes four types of echo structures were analyzed statistically for the 11 rainfallepisodes shallowconvectiveechoes sce deepconvectivecores dcc wideconvectiveechocores wcc and broad stratiform bsr echo regions sce and dcc events were most frequent before the maximum rainfall with the peak frequency of sce leading that of dccs wccs were most frequent during therainfallmaximum and bsr regionswere most frequentinthe later part oftherainfallepisode composited ecmwf interim re analysis era interim data and 3 hourly atmospheric soundings indicate that the 2 4 day episodes were related to the passage of equatorial waves in the early part of a rainfall episode the wave passageconditionswereunstable favoringdeeppenetratingconvectiveelements whileinthelaterperiod the wave divergence profile was commensurate with convective systems in late anvil producing stages these results support the stretched building block notion of the life cycle of tropical convection and confirm satellitebased interpretations of sce dcc wcc and bsr statistics in the composition of the convective population

time space characteristics of diurnal rainfall over borneo and surrounding oceans as observed by trmm pr abstract five years of tropical rainfall measuring mission trmm precipitation radar pr data were used to investigate the time and space characteristics of the diurnal cycle of rainfall over and around borneo an island in the maritime continent the diurnal cycle shows a systematic modulation that is associated with intraseasonal variability in the large scale circulation pattern with regimes associated with low level easterlies or westerlies over the island the lower tropospheric westerly easterly components correspond to periods of active inactive convection over the island that are associated with the passage of intraseasonal atmospheric disturbances related to the madden julian oscillation a striking feature is that rainfall activity propagates to the leeward side of the island between midnight and morning the inferred phase speed of the propagation is about 3 m s 1 in the easterly regime and 7 m s 1 in the westerly regime propagation occurs over the entire island causing a leeward enhan

san andreas fault zone head waves near parkfield california microearthquake seismograms from the borehole seismic network on the san andreas fault near parkfield california provide three lines of evidence that first p arrivals are head waves refracted along the cross fault material contrast first the travel time difference between these arrivals and secondary phases identified as direct p waves scales linearly with the source receiver distance second these arrivals have the emergent wave character associated in theory and practice with refracted head waves instead of the sharp first breaks associated with direct p arrivals third the first motion polarities of the emergent arrivals are reversed from those of the direct p waves as predicted by the theory of fault zone head waves for slip on the san andreas fault the presence of fault zone head waves in local seismic network data may help account for scatter in earthquake locations and source mechanisms the fault zone head waves indicate that the velocity contrast across the san andreas fault near parkfield is approximately 4 percent further studies of these waves may provide a way of assessing changes in the physical state of the fault system

convectively coupled equatorial waves 1 convectively coupled equatorial waves ccews control a substantial fraction of tropical rainfall variability their horizontal structures and dispersion characteristics correspond to matsuno s 1966 solutions of the shallow water equations on an equatorial beta plane namely kelvin equatorial rossby mixed rossby gravity and inertio gravity waves because of moist processes the tilted vertical structures of ccews are complex and their scales do not correspond to that expected from the linear theory of dry waves the dynamical structures and cloud morphology of ccews display a large degree of self similarity over a surprisingly wide range of scales with shallow convection at their leading edge followed by deep convection and then stratiform precipitation mirroring that of individual mesoscale convective complexes ccews have broad impacts within the tropics and their simulation in general circulation models is still problematic although progress has been made using simpler models a complete understanding of ccews remains a challenge in tropical meteorology

quantifying near field and off fault deformation patterns of the 1992 mw 7 3 landers earthquake coseismic surface deformation in large earthquakes is typically measured using field mapping and with a range of geodetic methods e g insar lidar differencing and gps current methods however either fail to capture patterns of near field coseismic surface deformation or lack preevent data consequently the characteristics of off fault deformation and the parameters that control it remain poorly understood we develop a standardized method to fully measure the surface near field coseismic deformation patterns at high resolution using the cosi corr program by correlating pairs of aerial photographs taken before and after the 1992 m w 7 3 landers earthquake cosi corr offers the advantage of measuring displacement across the entire zone of surface deformation and over a wider aperture than that available to field geologists for the landers earthquake our measured displacements are systematically larger than the field measurements indicating the presence of off fault deformation we show that 46 of the total surface displacement occurred as off fault deformation over a mean deformation width of 154 m the magnitude and width of off fault deformation along the rupture is primarily controlled by the macroscopic structural complexity of the fault system with a weak correlation with the type of near surface materials through which the rupture propagated both the magnitude and width of distributed deformation are largest in stepovers bends and at the southern termination of the surface rupture we find that slip along the surface rupture exhibits a consistent degree of variability at all observable length scales and that the slip distribution is self affine fractal with dimension of 1 56

barrier effect of the indo pacific maritime continent on the mjo perspectives from tracking mjo precipitation abstractexplanations for the barrier effect of the indo pacific maritime continent mc on the mjo should satisfy two criteria first they should include specific features of the mc namely its intricate land sea distributions and elevated terrains second they should include mechanisms for both the barrier effect and its overcoming by some mjo events guided by these two criteria a precipitation tracking method is applied to identify mjo events that propagate across the mc mjo c and those that are blocked by the mc mjo b about a half of mjo events that form over the indian ocean propagate through the mc most of them 75 become weakened over the mc the barrier effect cannot be explained in terms of the strength horizontal scale or spatial distribution of mjo convection when it approaches the mc from the west a distinction between mjo b and mjo c is their precipitation over the sea versus land in the mc region mjo c events rain much more over the sea than over land whereas rainfall over

regional simulation of the october and november mjo events observed during the cindy dynamo field campaign at gray zone resolution abstractthis study investigates the october and november mjo events observed during the cooperative indian ocean experiment on intraseasonal variability in the year 2011 cindy dynamics of the mjo dynamo field campaign through cloud permitting numerical simulations the simulations are compared to multiple observational datasets the control simulation at 9 km horizontal grid spacing captures the slow eastward progression of both the october and november mjo events in surface precipitation outgoing longwave radiation zonal wind humidity and large scale vertical motion the vertical motion shows weak ascent in the leading edge of the mjo envelope followed by deep ascent during the peak precipitation stage and trailed by a broad second baroclinic mode structure with ascent in the upper troposphere and descent in the lower troposphere both the simulation and the observations also show slow northward propagation components and tropical cyclone like vortices after the passage of the mjo active phase

diversity of fault zone damage and trapping structures in the parkfield section of the san andreas fault from comprehensive analysis of near fault seismograms summary we perform comprehensive analyses of trapped waves and signals of damaged fault zone rocks associated with time delays of body waves along the parkfield section of the san andreas fault saf waveforms generated by thousands of earthquakes and recorded by near fault stations in several permanent and temporary deployments are examined with attention to the possible influence of a lithology contrast across the fault on signals of the low velocity damage zone clear candidate trapped waves are identified at only three stations mmnb and two of the other near fault stations flip and pies further to the nw clear candidate trapped waves are not seen at any of the near fault stations to the se of mmnb the locations of the events generating good candidate trapped waves at mmnb and the other two stations are not distributed broadly in space but clustered in a small number of locations moreover events that generate clear candidate trapped waves at one station do not typically generate trapped waves at the other two stations these observations imply that the damage zone is highly variable along strike and that a coherent connected waveguide does not exist for distances along strike larger than at most 3 5 km the distance between stations synthetic waveform fits for observed trapped waves at stations mmnb and flip indicate that the most likely parameters of the trapping structures at these locations are widths of about 150 m depths of about 3 km velocity reductions of 30 40 per cent and q values of 10 40 synthetic calculations of trapped waves demonstrate that if there is a contrast of seismic velocity across the fault the trapped waves are delayed relative to the s wave arrival trapped waves at station mmnb and to a lesser extent also at stations flip and pies in the nw section show this characteristic this suggests a lithology contrast in the top few km at these locations in agreement with results from tomography and studies of head waves in the parkfield area at several mini across fault arrays where trapped waves are not observed a low velocity damage zone is detected from the delay in the arrival time of body wave phases relative to a nearby off fault station the observed delay of the s wave is greater than the p wave delay consistent with the existence of a damage zone with poisson ratio of about 0 33 the observations of time delays without trapped waves indicate that parts of the damage zone are insufficiently coherent to generate trapped waves a broader damage zone may exist in the region between the saf and the south west fracture zone the results highlight the diversity of damage structures along the 40 km of the saf examined in this study and imply that fault imaging based on data at single sites does not necessarily apply to a larger section

recurrence interval of big earthquakes along the atotsugawa fault system central japan results of seismo geological survey 1 the atotsugawa fault system afs characterized by high seismicity of micro earthquakes is an active zone of right lateral strike slip faults in central japan we carried out seismo geological studies of three sites on the system one is in the middle of the master atotsugawa fault agf one is at the end and another is on a branching mozumi sukenobe fault msf trenching surveys demonstrated a maximum recurrence interval of 3 000 years which is similar to that of the central agf 2 500 years this might indicate a uniform behavior in the seismogenic zone despite the apparent segmentation in the shallower agf another geo slicing survey at msf depicted a scarce interval of 13 500 years about six times longer than that of the master fault two simultaneous events on both agf and msf occurred in 1858 a d and at about 17 300 years ago suggesting an intermittent cooperation between the master and branch faults of afs

diurnal forcing and phase locking of gravity waves in the maritime continent abstractan unfiltered zonal hovmoller depiction of rainfall in the maritime continent mc reveals remarkable spatiotemporal continuity of zonally propagating disturbances with a diurnal period wh

joint inversion of fault zone head waves and direct p arrivals for crustal structure near major faults a newly recognized class of seismic phases namely fault zone head waves arising from refraction at a transfault velocity contrast provides additional constraints to direct p waves in inversions of near fault arrival time data for earthquake location and velocity structure incorporation of fault zone head waves in the inversion process increases the available data and broadens the spatial coverage of ray paths between sources and receivers equally important the explicit recognition of fault zone head waves eliminates a source of error resulting from misidentifying head wave first arrivals as direct p waves a simple algorithm for the joint inversion of fault zone head waves and direct p phases is illustrated with observed and synthetic data application to a small data set recorded by the borehole seismic network at parkfield california provides separate seismic velocity depth profiles for the crustal blocks on the two sides of the san andreas fault for depths less than 3 km the obtained velocity contrast is 10 20 for greater depths it decreases to 3 7 numerical tests with synthetic data show that for sources with known locations and for well located local earthquakes randomized mislocation errors of up to 600 m proper use of fault zone head waves can significantly improve the accuracy of the fitted velocity structure the results of this work motivate the inclusion of fault zone head waves in state of the art joint structure hypocenter inversions using high quality near fault data

fault zone waves observed at the southern joshua tree earthquake rupture zone waveform and spectral characteristics of several aftershocks of the m 6 1 22 april 1992 joshua tree earthquake recorded at stations just north of the indio hills in the coachella valley can be interpreted in terms of waves propagating within narrow low velocity high attenuation vertical zones evidence for our interpretation consists of 1 emergent p arrivals prior to and opposite in polarity to the impulsive direct phase these arrivals can be modeled as headwaves indicative of a transfault velocity contrast 2 spectral peaks in the s wave train that can be interpreted as internally reflected low velocity fault zone wave energy and 3 spatial selectivity of event station pairs at which these data are observed suggesting a long narrow geologic structure the observed waveforms are modeled using the analytical solution of ben zion and aki 1990 for a plane parallel layered fault zone structure synthetic waveform fits to the observed data indicate the presence of ns trending vertical fault zone layers characterized by a thickness of 50 to 100 m a velocity decrease of 10 to 15 relative to the surrounding rock and a p wave quality factor in the range 25 to 50

why does the mjo detour the maritime continent during austral summer eastward propagation of the madden julian oscillation mjo detours the maritime continent mc region southward during austral summer exhibiting enhanced convective activity preferentially in the southern part of the mc area with much weaker anomalies in the central mc area column integrated moist static energy budget of the mjo is analyzed to understand the processes responsible for the mjo detouring results show that zonal and meridional moisture advection is the essential process to the mjo detouring causing the difference between the southern and central mc regions in the moisture recharge before and during the mjo onset further analysis reveals that moisture advection by mjo perturbation winds acting upon the background moisture gradient has the dominant contribution to the regional contrast between the central and southern mc areas the zonal moisture advection is greater in the southern mc region because the zonal gradient of the background moisture field is much steeper in the southern mc area than in the central mc area the onset of the australian monsoon in austral summer contributes to the establishment of the sharp zonal moisture gradient in the southern mc region the meridional moisture advection is weaker in the central mc area because meridional wind anomalies associated with the mjo vary regionally presumably through interactions with the topography and land sea contrast

diabatic divergence profiles in western pacific mesoscale convective systems abstract heating in the atmosphere can be expressed as diabatic divergence d which is nearly equal to the actual horizontal divergence in tropical convection high quality profile measurements from airborne doppler radar purls in ten mesoscale convective systems mcs observed during toga coare are examined and the mean profile is compared with rawinsonde array measurements young convective features have strong near surface convergence while older cells with better developed downdrafts and stratiform precipitation areas have their peak convergence aloft in the mean then surface flow is only weakly convergent or oven divergent so that the main convergence into mcss is deep and peaked aloft with a sharp melting convergence at 0 c divergence prevails above 10 km altitude but was undersampled by the radar unusual but well sampled observations in the purl dataset include a persistent widespread profile feature in one well sampled mcs a cyclone rainband oscillatory reverberations c

diurnal patterns of rainfall in northwestern south america part ii model simulations abstract this second paper of a three part series documents the ability of the fifth generation pennsylvania state university ncar mesoscale model mm5 to successfully replicate some known aspects of the rainfall of northwestern south america the success of the control simulation justifies the use of the model in part iii for sensitivity experiments and more detailed diagnosis the simulation is produced using multiply nested grids with grid increments from 72 km down to 2 km three coarser resolution grids are integrated for a period of 10 days with the finest resolution grid run for a 2 day subset of that period several features of the rainfall field are examined as metrics of the model s performance on the largest scales the model reasonably simulates easterly waves in the western atlantic and caribbean although it tends to develop them into tropical cyclones too readily over the amazon river basin diurnally initiated rainbands are observed to propagate westward crossing the basin in 2 3 day

key processes for the eastward propagation of the madden julian oscillation based on multimodel simulations as a prominent climate variability mode with widespread influences on global weather extremes the madden julian oscillation mjo remains poorly represented in the latest generation of general circulation models gcms with a particular challenge in simulating its eastward propagating convective signals in this study by analyzing multi model simulations from a recent global mjo model evaluation project an effort is made to identify key processes for the eastward propagation of the mjo through analyses of moisture entropy me processes under a moisture mode framework for the mjo the column integrated horizontal me advection is found to play a critical role for the eastward propagation of the mjo in both observations and good mjo models with a primary contribution through advection of the lower tropospheric seasonal mean me by the mjo anomalous circulations by contrast the horizontal me advection effect for the eastward propagation is greatly underestimated in poor mjo gcms due to model deficiencies in simulating both the seasonal mean me pattern and mjo circulations leading to a largely stationary mjo mode in these gcms these results thus pinpoint an important guidance towards improved representation of the mjo in climate and weather forecast models while this study mainly focuses on fundamental physics for the mjo propagation over the indian ocean complex influences by the maritime continent on the mjo and also me processes associated with the mjo over the western pacific warrant further investigations

shallow structure of the landers fault zone from explosion generated trapped waves with fault zone trapped waves generated by near surface explosions within the fault zone of the 1992 landers california earthquake and recorded by linear seismic arrays deployed along and across the fault we have delineated the shallow seismic structure near the 30 km long southern rupture on the johnson valley fault the explosion excited trapped waves with relatively large amplitude and long duration wave train after the s waves are similar to those generated by aftershocks li et al 1994a b but have lower frequencies and travel more slowly coda normalized amplitude spectra of explosion excited trapped waves show a maximum at 2 hz which decreases rapidly with the station offset from the fault trace on the cross fault profiles normalized amplitudes of trapped waves on the along fault profile also decreased with distance between the explosion and station giving an apparent q of 18 at 1 2 hz in the fault zone for the shot near the profile the dispersion of trapped waves from 0 6 to 2 5 hz recorded on this along fault profile implies a shear velocity of 1 0 km s for the fault zone and 1 8 km s for the wall rock while the data from the farther shot show an increase in velocity and q with depth measured group velocities and q values were used as constraints in the numerical modeling of trapped waves on cross fault and along fault profiles results reveal that the shallow johnson valley fault is marked by a zone 250 m wide where the shear velocity is 1 km s and q is 20 calculation of finite difference synthetics for a depth varying fault structure show that these model parameters apply to the depth of 1 km below which the fault zone shear velocity increases to 1 9 km s and q increases to 30

three dimensional calculations of fault zone guided waves in various irregular structures summary the detailed structure of fault zones fzs plays an important role in problems related to fault mechanics earthquake rupture wave propagation and seismic hazard fzs are thought to consist of an o 10 100 m wide region of decreased seismic velocity but structural details such as their depth extent lateral and vertical variations etc are elusive the small spatial scales involved make such structures difficult to image with ray theoretical methods such as tomography however seismic energy trapped inside fz layers can provide dispersive wave trains that carry information on the fz structure these waves can travel many kilometres inside the fz before reaching the surface and are therefore strongly altered by its properties candidate trapped waves have been observed above several active faults inversion algorithms exist that can model these observations in terms of planar fault zone structures however at present it is not clear how reliable these estimates are as the effects of even small 3 d variations on trapped waves are not well understood the goal of this study is to distinguish 3 d structures that do and do not significantly affect fz waves to achieve this we perform numerical calculations of wave propagation in various fz geometries and analyse the waveforms spectra and envelopes of the synthetic seismograms the main results are that 1 moderate changes of the shape of fz or 2 small scale heterogeneities or 3 depth dependent properties do not strongly affect the observed fz waves in contrast strong effects are to be expected from 4 breaks in the continuity of fz structure e g offsets which may at some point allow imaging of such features at depth

gregarious tropical convection abstract a beat source with a vertical profile like that of observed tropical mesoscale convective systems mcss is shown to cause through inviscid gravity wave dynamics upward displacement at low levels in a mesoscale region surrounding the heating typical values are 10 30 area contraction at the surface everywhere within 270 km of the heating 6 h after it starts as a result conditions near an existing mcs but beyond the area of mcs outflow become more favorable for the development of additional convection this theory predicts that cloud clusters should be gregarious infrared satellite imagery confirms that almost half of the cold cloudiness observed in a month over the oceanic warm pool region was contributed by just 14 objectively defined multiday supercluters

the role of global circumnavigating mode in the mjo initiation and propagation a series of convection permitting regional model simulations are used to study the influences of intraseasonal forcings from the periphery of the tropical indian ocean on the october 2011 mjo event well observed during the dynamics of the madden julian oscillation dynamo field campaign these sensitivity experiments demonstrate the predominant role of a global circumnavigating mode in the initiation and propagation of this mjo event although the regional framework would not completely rule out influences from the extratropics through the western boundary of the model domain it is found that filtering out intraseasonal forcing leads to the absence of kelvin waves which may reduce moisture transport and weakened lower level convergence at the leading edge of the westerlies and further leads to diminishing mjo signatures in these sensitivity experiments meanwhile for the same regional domain initiated two weeks before the onset of the mjo convection there is little impact of whether or not the global mjo signals retained in the initial conditions on the other hand the removal of the global mjo signals from the lateral boundary conditions will not affect the propagation of the mjo after it has been initiated in the regional model domain

study of the 1999 m 7 1 hector mine california earthquake fault plane by trapped waves we recorded fault zone trapped waves from aftershocks on portable seismometers in a tight linear array across the lavic lake fault which was one of several faults that ruptured in the m 7 1 hector mine california earthquake on 16 october 1999 trapped waves with large amplitudes and long duration at 4 to 7 hz produced by aftershocks occurring within the rupture zone were recorded at stations close to the fault trace however the s waves registered at stations farther from the rupture zone for the same events were much briefer trapped waves recorded at the hector mine rupture zone are similar to those observed in the landers rupture zone li et al 1994a b but show higher frequencies simulations of these trapped waves indicate a 75 to 100 m wide low velocity and low q waveguide along the hector mine rupture zone in which the s velocity is reduced by about 40 to 50 from wall rock velocities and q is 10 to 60 in the depth range from the surface to 10 km we interpret this low velocity waveguide as being a remnant of the process zone formed by inelastic deformation around the propagating crack tip during dynamic rupture in the 1999 hector mine earthquake the reductions of velocities and q within the hector mine rupture zone are similar to those within the landers rupture zone suggesting that the fault zone rock was damaged to the same degree in the two earthquakes the wave guide width 75 100 m on the hector mine rupture zone 40 km in the total length is half that 150 250 m of the landers rupture zone 80 km in the total length consistent with the scaling of process zone size to rupture length as predicted in some published dynamic rupture models locations of aftershocks for which we observed trapped waves show bifurcation of the northern hector mine rupture at depth although only the west rupture branch broke to the surface