tide gage response to tsunamis part ii other oceans and smaller seas abstract extending previous work in the north pacific tsunami response was examined in the atlantic and indian oceans and in three smaller seas with the objective of exploring scale effects energy diffusing from the chilean tsunami of 22 may 1960 was tracked through windows around antarctica into all three oceans simultaneously reaching maximum intensity about 39 h after quake time in smaller seas spectral response was again characteristically an exacerbation of normal background with principal energy in the fundamental pumping mode of the local coastal shelf subsequent to diffusion isotropic energy decay was uniformly exponential except that the diffusion and decay e folidng times were different in each sea an ad hoc energy flux decay model with a constant linear friction coefficient suffices to explain the observed decay times in terms of basin geometries the model has several spinoffs it accounts for about half the observed coastwise variation in tsunami intensity it may possibly

some tsunami characteristics deducible from tide records abstract after an initial 40 hour diffusion period the time decay of tsunami variance was found to be uniformly exponents for 28 events among eight pacific tide stations thew results essentially confirm munk s acoustic deny hypothesis except that the decay e folding time 22 h more nearly equated the ocean s normal mode transit time 21 h than munk s mean collision time 14 h relative tsunami energy obtained by extrapolating exponential decay back to t 0 was found to be similarly ranked among tsunamis at all stations and roughly proportional to seismic energy a total energy estimate for the tsunami of 9 march 1957 obtained by correcting the observed energy decay at wake island for instrument and island response provided normalized total energy estimates for all tsunamis that were consistent with independent estimates by kajiura and by aida similarities between power spectra computed from these time series suggests that station response is primarily linear normal mode forcing of the conti

variable density flow and solute transport simulation of regional aquifers containing a narrow freshwater saltwater transition zone variable density flow and solute transport simulation of aquifer systems containing narrow transition zones between freshwater and saltwater requires particular attention to certain aspects of the numerical method and its application to be successful typically only cases involving wide transition zones have been simulated with variable density transport models possibly because of inaccuracies in the modeling approaches used the major components of a successful approach are threefold first functionally consistent approximation of terms involved in fluid velocity calculations is necessary in the case of galerkin finite element methodology a significant modification is required to the standard approach in order to achieve consistency second the simulator must be verified in a particular series of tests the usual tests using henry s problem for verification of density dependent transport simulators are inadequate to check for consistency of the velocity approximations and for the accuracy of simulating flow driven by bouyancy forces third adequately fine spatial discretization is required when applying the simulator for spatial stability of the numerical transport solution and to allow accurate representation of narrow transition zones and the effects of low transverse dispersivity the effectiveness of this approach is demonstrated through simulation of the flow of fresh and saline groundwater in the layered basalt aquifer of southern oahu hawaii the transition zone in this regional flow system is narrow except near the discharge area where it is broadly dispersed simulation of this common situation with an inconsistent approximation gives grossly incorrect results while simulation with a consistent model provides a robust tool for analysis of system hydrology

the dual source region for the 2004 sumatra tsunami 1 wave arrival times obtained from coastal tide gage and satellite altimetry records for the indian ocean are used to delineate the source region for the december 26 2004 sumatra tsunami findings define a curved 250 km wide 1000 km long tsunami source region centered over the sunda subduction zone which closely matches the seismic source estimated from broadband geophysical data imbedded in this general region are hot spots associated with the southern fast slip and northern slow slip domains which served as distinct source areas for the destructive waves that inundated the coast of the indian ocean

extracting the 2004 indian ocean tsunami signals from sea surface height data observed by satellite altimetry 1 altimeter equipped satellites flew over the propagating area of the indian ocean tsunami caused by the 2004 sumatra andaman earthquake on 26 december 2004 tsunami signals can be detected as differences in sea level changes of multiple tracks however observed changes in sea level differences involve not only tsunami signals but also effects from various ocean phenomena and errors due to observation technology and data processing a multisatellite time spatial interpolation method is performed to define reference sea surface heights after applying the method to the products on sea level anomalies along tracks of altimeter equipped satellites quality tsunami height profiles with only 4 to 5 cm root mean square errors were obtained for the indian ocean tsunami along five tracks from four satellites jason 1 topex poseidon envisat and geosat follow on maximum tsunami height in the open ocean for the 2004 indian ocean tsunami as observed from satellite altimetry was 1 1 m trough to crest 115 min after the main shock reliable tsunami height profiles from satellite altimetry were extracted for the first time the method employed in this study has the potential to extract tsunami signals of 0 1 m or greater trough to crest height from satellite altimetry observation data on the deep sea by ongoing satellite missions

tide gauge observations of the indian ocean tsunami december 26 2004 the magnitude 9 0 earthquake centered off the west coast of northern sumatra 3 307 n 95 947 e on december 26 2004 at 00 59 utc united states geological survey usgs 2005 usgs earthquake hazards program latest earthquakes earthquake hazards program http earthquake usgs gov eqinthenews 2004 usslav 2005 generated a series of tsunami waves that devastated coastal areas throughout the indian ocean tide gauges operated on behalf of national and international organizations recorded the wave form at a number of island and continental locations this report summarizes the tide gauge observations of the tsunami in the indian ocean available as of january 2005 and provides a recommendation for the use of the basin wide tide gauge network for future warnings

a 3 d prognostic numerical model study of the georges bank ecosystem part i physical model abstract the influence of tidal forcing and tidal and wind mixing on circulation and stratification over georges bank and adjacent regions in the gulf of maine has been examined using the 3 d semi implicit version of the blumberg and mellor 1987 primitive equation ocean circulation model the numerical domain covered the gulf of maine georges bank region with an open boundary starting at the new jersey coast and ending at the nova scotia coast with increased spatial resolution over georges bank numerical experiments were conducted using both smoothed and non smoothed high resolution 15 s bottom topography the model was forced by specifying the m 2 elevation and phase on the open boundary and several forms of the bottom roughness parameter z o were used the model provided a reasonable simulation of the m 2 tidal elevations and currents the model when run as an initial value problem with early summer stratification exhibited tidal mixing fronts around the 40 60 m isobath over georges bank and nantucket shoals and 100 m isobath on brown bank the formation of these tidal mixing fronts significantly enhanced the along isobath tidal rectified current over georges bank and the other two shoal regions a cool water band developed within the frontal zone along the eastern and southern flanks of georges bank and nantucket shoal and it became cooler owing to wind mixing and upwelling as a mean summer wind stress was added tidal mixing and turbulent dissipation varied in time asymmetrically over georges bank over georges bank tidal mixing was generally characterized as a local 1 d balance between turbulent shear production and dissipation the spatial structure of the tidal residual flow and local turbulent dissipation rate depended critically on the spatial resolution of the bottom topography and the spatial distribution of z 0 analysis of the 3 d momentum balance and the residual flow over the center of georges bank indicates that earlier results based on a 2 d cross bank model correctly captured the basic dynamics of stratified tidal rectification and tidal mixing in this idealized model setting

vertical structure of turbulence on the southern flank of georges bank microstructure and acoustic doppler current profiler measurements were taken at two sites on georges bank in a shallow 45 m well mixed region on top of the bank and in a deeper 75 m more stratified region on the southern flank each site was visited twice april 25 to may 3 1995 and june 6 16 1995 at both sites the dominant variability in the turbulent kinetic energy dissipation rate e was related to the semidiurnal m2 tide in the well mixed lower portions of the water column a phase delay was observed between e and the current speed the delay increased with height above the bottom there was also a depth dependent phase delay in the square of the vertical shear of horizontal velocity s2 of the m2 component this phase lag has a depth dependence similar to that found for e which suggests that the turbulent mixing is locally generated by the current shear as opposed to having propagated from the boundary

comment on the great sumatra andaman earthquake of 26 december 2004 lay et al research articles 20 may 2005 p 1127 estimated a 600 km length for the tsunami source region adding tide gauge data from paradip the northernmost of the indian east coast stations and therefore the most critical constraint on the northern extent of the source we estimate that its length was greater by 30

the vertical structure of turbulent dissipation in shelf seas abstract the free fall fly profiler has been used to determine the variation in energy dissipation in the water column over a tidal cycle at mixed and stratified sites in the irish sea it was found that exhibits a strong m4 variation with a pronounced phase lag that increases with height above the bed in mixed conditions this m4 signal which extends throughout the water column is reasonably well reproduced by turbulent closure models of the vertical exchange in the summer stratified situation the m4 signal in is confined to about 40 m above the seabed with phase delays of more than 4 h relative to the seabed the lowest levels of dissipation 10 5 w m 3 measured in the pycnocline are significantly above the system noise level and much higher than predicted by a model using the mellor yamada level 2 closure scheme my2 0 however when allowance is made for the diffusion of tke the model my2 2 simulates the depth time distribution of dissipation in the stratified case satisfactorily if

karst aquifer evolution in fractured porous rocks the evolution of flow in a fractured porous karst aquifer is studied by means of the finite element method on a two dimensional mesh of irregularly spaced nodal points flow within the karst aquifer is driven by surface recharge from the entire region simulating a precipitation pattern and is directed toward an entrenched river as a base level during the early phase of karstification both the permeable rock matrix modeled as triangular elements and fractures within the rock matrix modeled as linear elements carry the flow as the fractures are enlarged with time by chemical dissolution within the system calcite carbon dioxide water flow becomes more confined to the fractures this selective enlargement of fractures increases the fracture conductivity by several orders of magnitude during the early phase of karstification thus flow characteristics change from more homogeneous pore controlled flow to strongly heterogeneous fracture controlled flow we study several scenarios for pure limestone aquifers mixed sandstone limestone aquifers and various surface recharge conditions as well as the effect of faulting on the aquifer evolution our results are sensitive to initial fracture width faulting of the region and recharge rate

a numerical study of stratified tidal rectification over finite amplitude banks part ii georges bank abstract tidal rectification over a two dimensional finite amplitude symmetrical bank is studied using the blumberg and mellor primitive equation coastal ocean circulation model ecom si in the homogeneous case the nonlinear interaction of tidal currents with the variable bottom topography generates an along isobath residual circulation over the bank which tends to increase as either the slope or height of the bank is increased in the stratified case internal waves at tidal and higher frequencies are generated over the sloping sides of the bank tidal mixing occurs in the bottom boundary layer leading to horizontal tidal mixing fronts the resulting stratified tidal rectification associated with the tidal mixing front the generation of internal tides and the modification of internal friction due to stratification leads to a subsurface intensification of the along isobath residual current at the front and at the top of the bottom mixed layer over the slope and a cross bank double cell circulation

the landslide tsunami of november 3 1994 skagway harbor alaska we show that the tsunami of november 3 1994 in skagway alaska was generated by an underwater landslide formed during the collapse of a cruise ship wharf undergoing construction at the head of taiya inlet this event occurred at a time of extreme low tide and was not associated with a regional seismic event or incoming oceanic tsunami persistent wave motions with an amplitude of 1 m and a period of 3 min recorded by a tide gauge in skagway harbor following the landslide are linked to the formation of a cross inlet seiche and quarter wave resonance within the harbor the high q factor for the harbor q 20 indicates weak dissipation and strong resonance within the harbor

exchange of water between conduits and matrix in the floridan aquifer flow through carbonate aquifers may be dominated by conduits where they are present by intergranular or fracture porosity where conduits are missing or may occur in conduits and matrix porosity where both are well developed in the latter case the exchange of water between conduits and matrix could have important implications for water management and hydrodynamic modeling an extensive conduit system has been mapped by dye trace studies and cave diving exploration at the santa fe sinkrrise system located in largely unaltered rocks of the floridan aquifer of north central florida in this area the santa fe river flows underground at the river sink and returns to the surface 5 km to the south at a first magnitude spring called the river rise limited data show that discharge is greater by 27 96 at the river rise than at the sink and that the downstream increase in discharge is inversely related to discharge of the river natural so 2y 4 concentrations indicate that 25 of the water discharging from the rise originates from the sink during low flow conversely so 2y and other solute concentrations indicate that most of the water discharging from the rise originates from 4 the sink during floods ar 40 decrease in na q and cl y concentrations over a 5 1r2 month period at a down gradient water supply well may reflect flow of dilute flood water from the conduits into and through the matrix at rates estimated to be between 9 and 65 mrday calcium concentrations remain constant through time at the well although flood waters have 90 lower ca 2q concentrations than ground water perhaps reflecting dissolution of the matrix rocks this apparent exchange of water between matrix and conduits is important for regional ground water quality and dissolution reactions q 2001 published by elsevier science b v

early development of karst systems 2 turbulent flow a simulation model developed to explore patterns of fracture enlargement within incipient limestone karst aquifers has been extended to turbulent flow in contrast to the highly selective passage enlargement that occurs early in cave network development under laminar flow the transition to turbulent flow results in more general passage enlargement leading to maze networks when initial fractures are large and hydraulic gradients are high these results support previously published hypotheses for the development of maze patterns including formation within structural settings that have created initially large fractures or within flow systems periodically inundated by flooding maze development is also favored under turbulent flow when passages are entirely water filled and where the groundwater flow system is long lived by contrast branched patterns are most common when passages become free surface subterranean streams because depression of the piezometric surface along main passages downcutting along main passages and possible infilling with sediment of side passages limit the sharing of discharge among interconnected fractures or bedding planes that promote maze development

spectral analysis of tsunami waves separation of source and topography effects a new approach is proposed to separate the influence of source and topography in observed tsunami spectra and to reconstruct the initial source spectrum the method assumes a linear tide gauge response to external forcing and is based on comparative analysis of tsunami and background spectra evaluation of the ratio of tsunami to background spectra gives functional characteristics that are invariant of station location and dependent only on the source parameters three events the urup tsunami of december 22 1991 northwest pacific the hokkaido southwest okushiri tsunami of july 12 1993 sea of japan and the shikotan tsunami of october 4 1994 northwest pacific are used as examples of the proposed approach the source spectra reconstructed from the analysis of different tide gauges were found to be in good agreement with each other and with the seismological geodetic and field survey data

the significance of turbulent flow representation in single continuum models 1 karst aquifers exhibit highly conductive features caused from rock dissolution processes flow within these structures can become turbulent and therefore can be expressed by nonlinear gradient functions one way to account for these effects is by coupling a continuum model with a conduit network alternatively turbulent flow can be considered by adapting the hydraulic conductivity within the continuum model consequently the significance of turbulent flow on the dynamic behavior of karst springs is investigated by an enhanced single continuum model that results in conduit type flow in continuum cells ctfc the single continuum approach ctfc represents laminar and turbulent flow as well as more complex hybrid models that require additional programming and numerical efforts a parameter study is conducted to investigate the effects of turbulent flow on the response of karst springs to recharge events using the new ctfc approach existing hybrid models and modflow 2005 results reflect the importance of representing 1 turbulent flow in karst conduits and 2 the exchange between conduits and continuum cells more specifically laminar models overestimate maximum spring discharge and underestimate hydraulic gradients within the conduit it follows that aquifer properties inferred from spring hydrographs are potentially impaired by ignoring flow effects due to turbulence the exchange factor used for hybrid models is necessary to account for the scale dependency between hydraulic properties of the matrix continuum and conduits this functionality which is not included in ctfc can be mimicked by appropriate use of the horizontal flow barrier package for modflow

submarine springs and coastal karst aquifers a review this article reports on current knowledge of coastal karst aquifers in which conduit flow is dominant and its aim is to characterise the functioning of these systems which are closely linked to the sea first earlier and recent studies of these aquifers are discussed on the basis of their findings it can be shown that two essential mechanisms are involved in the functioning of these systems i e aquifer discharge through submarine springs and saline intrusion through conduits open to the sea then the conditions that give rise to these aquifers are described and particular emphasis is placed on the influence of deep karstification when the sea level falls the base level variations are attributed to the glaciations or in the specific case of the mediterranean to the salinity crisis in the messinian period it is this inherited structure sometimes containing very deep conduits below sea level that today conditions the aquifer flow the flow in the conduits open to the sea depends on the hydraulic head gradient between the aquifer and the sea and is therefore a function of the water density and head losses in the aquifer this survey of coastal karst aquifers has revealed some common characteristics that show the development and or functional capacity of their karstic drainage networks a classification of such systems into three categories is proposed with the aim of assisting in the decision making concerning potential exploitation of water resources in coastal regions

modeling the salinity of an inland coastal brackish karstic spring with a conduit matrix model the salinity of an inland coastal brackish karstic spring is modeled on the basis of a simple concept of fluid exchange through head differences between a continuous porous matrix and a karst conduit the coastal aquifer is reduced to an equivalent porous medium matrix naturally invaded by seawater crossed by a single karst conduit where fresh water and brackish water mix in variable proportions and flow up into the spring a new numerical model with an upwind explicit finite difference scheme called salt water intrusion in karst conduits swikac was developed and successfully applied to the almyros spring of heraklio crete greece the good fit of the model to the observed salinity in the spring validates the proposed conceptual model of salinization it provides a quantitative description of the seawater intrusion inside the karst conduit the results open up new perspectives for managing the fragile and precious fresh water resources in karstic coastal zones

effects of dynamically variable saturation and matrix conduit coupling of flow in karst aquifers 1 well developed karst aquifers consist of highly conductive conduits and a relatively low permeability fractured and or porous rock matrix and therefore behave as a dual hydraulic system groundwater flow within highly permeable strata is rapid and transient and depends on local flow conditions i e pressurized or nonpressurized flow the characterization of karst aquifers is a necessary and challenging task because information about hydraulic and spatial conduit properties is poorly defined or unknown to investigate karst aquifers hydraulic stresses such as large recharge events can be simulated with hybrid coupled discrete continuum models since existing hybrid models are simplifications of the system dynamics a new karst model modbrac is presented that accounts for unsteady and nonuniform discrete flow in variably saturated conduits employing the saint venant equations model performance tests indicate that modbrac is able to simulate 1 unsteady and nonuniform flow in variably filled conduits 2 draining and refilling of conduits with stable transition between free surface and pressurized flow and correct storage representation 3 water exchange between matrix and variably filled conduits and 4 discharge routing through branched and intermeshed conduit networks subsequently modbrac is applied to an idealized catchment to investigate the significance of free surface flow representation a parameter study is conducted with two different initial conditions 1 pressurized flow and 2 free surface flow if free surface flow prevails the systems is characterized by 1 a time lag for signal transmission 2 a typical spring discharge pattern representing the transition from pressurized to free surface flow and 3 a reduced conduit matrix interaction during free surface flow

seismology speed and size of the sumatra earthquake we now have a clearer picture of the seismic features of last year s gigantic event our seismological results reveal that indonesia s devastating sumatra andaman earthquake on 26 december 2004 was 2 5 times larger than initial reports suggested second only to the 1960 chilean earthquake in recorded magnitude they indicate that it slowly released its energy by slip along a 1 200 km fault generating a long rupture that contributed to the subsequent tsunami now that the entire rupture zone has slipped the strain accumulated from the subduction of the indian plate beneath the burma microplate has been released and there is no immediate danger of a similar tsunami being generated on this part of the plate boundary although large earthquakes on segments to the south still present a threat

multiple cmt source analysis of the 2004 sumatra earthquake while it is agreed that the great sumatra earthquake of december 26 2004 was among the largest earthquakes of the past century there has been disagreement on how large it was which part of the fault ruptured and how the rupture took place we present a centroid moment tensor cmt analysis of the earthquake in which multiple point sources are used in the inversion to mimic a propagating slip pulse the final model consists of five point sources with the southernmost sources accounting for the majority of the moment release the presumed fault planes of the southern sources strike northwest while those in the north strike northeast consistent with the geometry of the subduction trench slip on the fault is found to be more oblique in the north than in the south the inversion with five sources leads to a moment magnitude for the sumatra earthquake of m w 9 3 consistent with estimates from long period normal mode amplitudes

tsunami magnitudes determined from ocean bottom pressure gauge data around japan 1 we develop a method to calculate tsunami magnitude from ocean bottom pressure gauge data around japan direct application of abe s equations to ocean bottom pressure gauge data underestimates tsunami magnitudes by about an order of magnitude this is because abe s equations were derived only from tsunami amplitudes measured at coastal tide gauges where tsunamis are amplified by the shoaling of waves and reflection at the coastline for offshore bottom pressure records we introduce correction factors to abe s original equations to account for tsunami amplitudes measured in open oceans the modified equations produce pressure gauge determined tsunami magnitudes close to those determined using coastal tide gauges

early development of karst systems 1 preferential flow path enlargement under laminar flow modeling of flow and solutional processes within networks of interconnected conduits in limestone aquifers indicates that enlargement occurs very selectively during the early stages of karst aquifer development under laminar flow if initial flow paths are uniform in size almost all enlargement occurs along a single set of connected conduits that lie along a direct path between recharge and discharge locations and are aligned along the hydraulic gradient with a sufficiently large variation in initial aperture widths enlargement occurs along the flow path offering the least resistance to flow but since flow rates in laminar flow are proportional to the fourth power of diameter but only linearly proportional to hydraulic gradient the preferentially enlarged set of fractures may follow an indirect path results disfavor earlier suggestions that nonselective cave patterns result from artesian flows at least under laminar flow conditions and that all passages should be competitive until the onset of turbulent flow

numerical modeling of the great 2004 indian ocean tsunami focus on the mascarene islands on 26 december 2004 the m w 9 2 sumatra earthquake triggered the greatest tsunami ever observed in recent times the unprecedented quality and variety of observations on modern instruments provide opportunities to refine modeling techniques as well as our perception of tsunami hazard in oceanic regions where historical events are not as frequent as in the pacific ocean we present a numerical modeling of the 2004 tsunami on the mascarene islands with refined computations on la reunion island where postevent survey observations and one tide gauge record are available we use two different source models models a and b to account for the observations and we also test an additional source model model c to study the effect of a tsunami originating in the 1833 epicentral area southern sumatra a wave trapped on the edge of la reunion may explain the greatest water heights reached in the western coastline of the island the observed tide gauge data are reasonably well fit models a and b the run up data can also be explained with our models late disturbances observed in la pointe des galets may be explained by a late tsunami reflection from madagascar or by harbor resonances finally we also show that model c 1833 like strikes la reunion more heavily than models a and b

rupture process of the 2004 sumatra andaman earthquake the 26 december 2004 sumatra andaman earthquake initiated slowly with small slip and a slow rupture speed for the first 40 to 60 seconds then the rupture expanded at a speed of about 2 5 kilometers per second toward the north northwest extending 1200 to 1300 kilometers along the andaman trough peak displacements reached 15 meters along a 600 kilometer segment of the plate boundary offshore of northwestern sumatra and the southern nicobar islands slip was less in the northern 400 to 500 kilometers of the aftershock zone and at least some slip in that region may have occurred on a time scale beyond the seismic band

the great sumatra andaman earthquake of 26 december 2004 the two largest earthquakes of the past 40 years ruptured a 1600 kilometer long portion of the fault boundary between the indo australian and southeastern eurasian plates on 26 december 2004 seismic moment magnitude mw 9 1 to 9 3 and 28 march 2005 mw 8 6 the first event generated a tsunami that caused more than 283 000 deaths fault slip of up to 15 meters occurred near banda aceh sumatra but to the north along the nicobar and andaman islands rapid slip was much smaller tsunami and geodetic observations indicate that additional slow slip occurred in the north over a time scale of 50 minutes or longer

georges bank residual circulation during weak and strong stratification periods prognostic numerical model results the seasonal extremes of the three dimensional residual circulation on georges bank are studied by numerically computing the circulation during weakly march april and strongly july august stratified periods the computations are performed using a prognostic i e including tidal time advection of the density field free surface nonlinear finite element model on realistic georges bank topography the dynamics considered result from the dominant m 2 tide baroclinic pressure gradients wind stress upstream boundary conditions and advanced turbulence closure comparison of these solutions with earlier diagnostic model results illustrates the importance of processes which could not be included in these earlier simulations such as density evolution and advanced turbulence closure in tidal time inclusion of nonlinear baroclinic effects improved treatment of other nonlinearities etc during the strongly stratified july august period the newly modeled processes intensify the residual circulation and result in recirculating transport on georges bank of 0 25 sv which is twice the diagnostic result the level of agreement between modeled and observed residual circulation improves very significantly for this period with the prognostic model predicting around bank currents as high as 46 cm s 1 in the frontal zone on the northeast peak analysis of the tidal time density and current structure in the frontal zone on the northeast peak indicates important tidal frequency dynamics and features which are supported by observational evidence during the weakly stratified march april period the dynamical impact of the newly modeled processes is small hence the prognostic and diagnostic models predict similar global structure with a recirculating transport on georges bank of 0 05 sv although there are local differences which result in the prognostic simulation agreeing more closely with the observed circulation

observations of the 2004 and 2006 indian ocean tsunamis from a pressure gauge array in indonesia 1 five shallow pressure gauges located in straits in the southern indonesian islands were used to evaluate tsunami signals triggered by the earthquakes off the northwest coast of sumatra in december 2004 and the south coast of java in july 2006 tsunami waves reached the pressure gauges around 5 to 6 hours after the 2004 earthquake the largest waves arrived 10 to 23 hours later with amplitudes ranging from 9 to 25 cm after the 2006 earthquake tsunami arrivals were only evident at the ashmore and roti pressure gauges in timor passage at these two gauges the first waves arrived around 2 25 hours after the earthquake and the largest waves arrived 2 to 3 hours later with amplitudes of 6 and 18 cm spectral analysis shows an increase of energy in the 40 to 80 min period band during the 2004 tsunami and at periods of 10 to 20 min in 2006 a simple ray tracing model of both the 2004 and 2006 events which approximates the tsunami as a shallow water wave was used to evaluate the effect of topography on tsunami propagation in order to provide a physical explanation for the features observed in the pressure gauge data

shallow water equations for equatorial tsunami waves we present derivations of shallow water model equations of korteweg de vries and boussinesq type for equatorial tsunami waves in the f plane approximation and discuss their applicability this article is part of the theme issue nonlinear water waves

meteorological tsunami of 19 march 2017 in the persian gulf observations and analyses on 19 march 2017 destructive tsunami like waves impacted the northeast shore of the persian gulf pg the maximum surveyed runup of about 3 m was observed at dayyer in southern iran where damaging waves inundated the land for a distance of 1 km and resulted in the deaths of five people because the pg has always been considered safe from extreme oceanic waves the event was totally unexpected in this study we examined sea level data from 12 stations across the pg and a variety of meteorological information including satellite imagery high altitude isohypse maps and high resolution air pressure records from 47 instruments along the pg our results show that the event was very local with recorded maximum trough to crest wave heights of 197 cm at dayyer and 234 cm at asaluyeh near field cities in iran located 80 km apart the dominant wave periods were in the range of 15 20 min at all distant tide gauges the observed wave heights were 35 cm no earthquakes or landslides were evident at the time of the event on the other hand atmospheric processes during 18 22 march were very active and 10 distinctive tsunamigenic air pressure disturbances were observed propagating over the pg suggesting that the event of 19 march 2017 was a meteorological tsunami atmospheric conditions over the pg were highly favourable for the generation of meteotsunamis and very similar to those that caused a chain of strong meteotsunamis in the mediterranean and black sea regions during 23 27 june 2014 based on the 500 hpa wind we evaluated that the disturbances had propagation speeds of 21 38 m s with the disturbance at dayyer having a speed of 26 m s toward 77 true the froude number fr estimated as the ratio of the air disturbance speed to the long wave speed on 19 march 2017 in the dayyer asaluyeh region was close to resonance fr 0 9 to 1 1 which is highly favourable for meteotsunami generation our findings indicate that the dayyer asaluyeh area is a hot spot that is highly vulnerable to extreme weather induced tsunami like waves

simulating long term nitrate n contamination processes in the woodville karst plain using cfpv2 with umt3d summary a research version of cfp conduit flow process code cfpv2 is applied with umt3d to simulate long term 1966 2018 nitrate n contamination transport processes in the woodville karst plain wkp northern florida where karst conduit networks are well developed groundwater flow in the wkp limestone porous matrix is simulated using darcy s law and non laminar flow within conduits is described by darcy weisbach equation nitrate n conduit transport and advective exchanges of groundwater and nitrate n between conduits and limestone matrix are calculated by cfpv2 and umt3d instead of modflow and mt3dms since reynolds numbers for flows in conduits are over the criteria of laminar flow the developed numerical model is calibrated by field observations and then applied to simulate nitrate n transport in the wkp the numerical simulations verify the theories that two sprayfields near the city of tallahassee and septic tanks in the rural area are major nitrate n point sources within the wkp high nitrate n concentrations occur near lost creek sink and conduits of wakulla spring and spring creek springs where aquifer discharge groundwater conduit networks control nitrate n transport and regional contaminant distributions in the wkp as nitrate n is transported through conduits rapidly and spread over large areas

source of the july 2006 west java tsunami estimated from tide gauge records 1 the source of the west java tsunami of july 17 2006 which was generated during a large earthquake near the sunda trench is constrained by tsunami waveforms that were recorded on six tide gauges around the indian ocean the tsunami travel times poorly constrain the source area probably because shallow bathymetry near these gauges is not well known inversion of tsunami waveforms however reveals that the tsunami source was about 200 km long the largest slip about 2 5 m for instantaneous rupture model was located about 150 km east of the epicenter most of the slip occurred on shallow parts of the fault indicating that this earthquake shares the same characteristics with tsunami earthquakes which generate abnormally large tsunamis compared with ground shaking the slip distribution yields a total seismic moment of 7 0 1020 nm mw 7 8

use of chemical and isotopic tracers to assess nitrate contamination and ground water age woodville karst plain usa concerns regarding ground water contamination in the woodville karst plain have arisen due to a steady increase in nitrate n concentrations 0 25 0 90 mg l during the past 30 years in wakulla springs a large regional discharge point for water 9 6 m3 s from the upper floridan aquifer ufa multiple isotopic and chemical tracers were used with geochemical and lumped parameter models exponential mixing em dispersion and combined exponential piston flow to assess 1 the sources and extent of nitrate contamination of ground water and springs and 2 mean transit times ages of ground water delta 15n no3 values 1 7 13 8 indicated that nitrate in ground water originated from localized sources of inorganic fertilizer and human animal wastes nitrate in spring waters 15n no3 5 3 8 9 originated from both inorganic and organic n sources nitrate n concentrations 1 0 mg l were associated with shallow wells open intervals less than 15 m below land surface elevated nitrate concentrations in deeper wells are consistent with mixtures of water from shallow and deep zones in the ufa as indicated from geochemical mixing models and the distribution of mean transit times 5 90 years estimated using lumped parameter flow models ground water with mean transit times of 10 years or less tended to have higher dissolved organic carbon concentrations lower dissolved solids and lower calcite saturation indices than older waters indicating mixing with nearby surface water that directly recharges the aquifer through sinkholes significantly higher values of ph magnesium dolomite saturation index and phosphate in springs and deep water 45 m relative to a shallow zone 45 m were associated with longer ground water transit times 50 90 years chemical differences with depth in the aquifer result from deep regional flow of water recharged through low permeability sediments clays and clayey sands of the hawthorn formation that overlie the ufa upgradient from the karst plain

response to comment on the great sumatra andaman earthquake of 26 december 2004 we support the revised estimate of tsunami source length 800 km obtained by neetu et al sea level monitoring with a high sampling rate good azimuthal coverage and real time access along with detailed bathymetry data around the stations would improve source region estimation from tsunami arrival times

tsunami source of the 2004 sumatra andaman earthquake inferred from tide gauge and satellite data tsunami source of the 2004 sumatra andaman earthquake was esti mated from a joint inversion of tsunami waveforms recorded on tide gauges and sea surface heights captured by satellite altimetry measurements the earthquake the largest in the past 40 years caused devastating tsunami damage to countries around the indian ocean but the tsunami source in particular its northern end was not well resolved although aftershocks and crustal deformation extended from off north western sumatra island through the nicobar islands to the andaman islands some seismic wave analyses indicated a shorter source length several hundred kilometers we used tsunami waveforms recorded at 12 tide gauge stations around the source and the sea surface heights measured by three satellites jason1 topex poseidon and envisat we numerically computed tsunami propagation using realistic bathym etry more than 66 000 depth points were digitized from nautical charts and combined with the etopo2 data inversion of satellite data indicates that the tsunami source extended to the andaman islands with a total length of 1 400 km but such a model produces much larger tsunami waveforms than observed at indian tide gauge stations inversion of tide gauge records and the joint inversion indicate that the tsunami source was about 900 km long the largest slip about 13 to 25 m was located off sumatra island and the second largest slip up to 7 m near the nicobar islands the slip distribution is similar for different rupture velocities and rise times with a slow velocity of 1 km sec and a rise time of 3 min yielding the largest variance reduction

the 2010 chilean tsunami off the west coast of canada and the northwest coast of the united states the major m w 8 8 chilean earthquake of 27 february 2010 generated a trans oceanic tsunami that was observed throughout the pacific ocean waves associated with this event had features similar to those of the 1960 tsunami generated in the same region by the great m w 9 5 1960 chilean earthquake both tsunamis were clearly observed on the coast of british columbia the 1960 tsunami was measured by 17 analog pen and paper tide gauges while the 2010 tsunami was measured by 11 modern digital coastal tide gauges four neptune canada bottom pressure recorders located offshore from southern vancouver island and two nearby open ocean dart stations the 2010 records were augmented by data from seven noaa tide gauges on the coast of washington state this study examines the principal characteristics of the waves from the 2010 event height period duration and arrival and travel times and compares these properties for the west coast of canada with corresponding properties of the 1960 tsunami results show that the 2010 waves were approximately 3 5 times smaller than the 1960 waves and reached the british columbia coast 1 h earlier the maximum 2010 wave heights were observed at port alberni 98 4 cm and winter harbour 68 3 cm the observed periods ranged from 12 min at port hardy to 110 120 min at prince rupert and port alberni and 150 min at bamfield the open ocean records had maximum wave heights of 6 11 cm and typical periods of 7 and 15 min coastal and open ocean tsunami records revealed persistent oscillations that rang for 3 4 days tsunami energy occupied a broad band of periods from 3 to 300 min estimation of the inverse celerity vectors from cross correlation analysis of the deep sea tsunami records shows that the tsunami waves underwent refraction as they approached the coast of vancouver island with the direction of the incoming waves changing from an initial direction of 340 true to a direction of 15 true for the second train of waves that arrived 7 h later after possible reflection from the marquesas and hawaiian islands

development of a discrete continuum vdfst cfp numerical model for simulating seawater intrusion to a coastal karst aquifer with a conduit system a hybrid discrete continuum numerical model variable density flow and solute transport conduit flow process vdfst cfp is developed to simulate seawater intrusion to a coastal karst aquifer with a conduit network the darcy weisbach equation is applied to simulate the nonlaminar groundwater flow in the conduit system that is conceptualized as pipes while the darcy equation is used for laminar groundwater flow in the continuum porous medium density dependent groundwater flow with appropriate additional density terms in the conduit is analytically derived the flow and transport equations are coupled and numerically solved by the finite difference method with an implicit iteration procedure two synthetic benchmarks are developed to compare the vdfst cfp model results with other numerical models such as the variable density seawat constant density continuum modflow mt3dms and constant density discrete continuum cfpv2 umt3d models the vdfst cfp model compares reasonably well with the other model results in both conduit and porous medium domains and well describes water and salt exchange between the two systems under turbulent flow conditions within the conduit the darcy weisbach equation calculates the flow rate more accurately without overestimation by the darcy equation sensitivity analysis indicates that conduit diameter friction factor matrix hydraulic conductivity and effective medium porosity are important parameters in the vdfst cfp model the pros and cons of the vdfst cfp model are discussed including the model assumptions and simplifications limitations of the discrete continuum modeling method and the convergence criteria in general the newly developed vdfst cfp model provides a new numerical modeling method for simulating seawater intrusion in a coastal karst aquifer with conduits

detection of karst conduit patterns via hydraulic tomography a synthetic inverse modeling study abstract karst aquifers are geologic media that consist of enlarged solution conduits the geometry of such conduits is very difficult to delineate and its hydraulic parameters such as hydraulic conductivity k and specific storage ss are difficult to estimate hydraulic tomography ht shown to successfully map the hydraulic heterogeneity of porous and fractured rock aquifers may also be effective in karst aquifers in this study we utilize two synthetic karst aquifers with the branchwork and network conduit patterns bcp and ncp to explore the ability of ht to map conduit patterns and their hydraulic parameters prior to the ht analysis forward models are built to study groundwater flow through synthetic karst aquifers to generate data and to gain insights into flow patterns forward modeling results reveal that 1 flow rates at the outlet of the bcp model is higher than the ncp model even when the same water injection rates are applied at the wells 2 the location of the injection well has a significant impact on the flow rate at the outlet and 3 flow lines mainly follow the conduit pattern these results suggest that the accurate mapping of karst networks is critical next the ht analysis of these data is conducted using a set of six models bcp and ncp to map the heterogeneity of different conduit systems under steady state and transient flow conditions inverse modeling results reveal that the estimated k maps become more reliable as the number of injection tests and the corresponding monitoring data are increased in the ht analysis moreover the results of the bcp model is closer to the original conduit pattern in comparison to the ncp model a comparative study of three inverse models with different number of observation wells and assuming the availability of geological data has shown that a more reliable pattern of the conduits can be mapped by adding geological information even when a small number of observation wells are available overall our results confirm the feasibility of ht in detecting major conduits as well as being able to differentiate between the bcp and ncp network types

influence of model geometrical fitting and turbulence parameterization on phytoplankton simulation in the gulf of maine abstract numerical experiments were made to examine the influences of model geometrical fitting and turbulence parameterization on the temporal and spatial distributions of simulated phytoplankton in the gulf of maine the assessment of the role of geometrical fitting was made by running a state of the art nutrient phytoplankton zooplankton npz model with physical fields provided from unstructured grid finite volume coastal ocean model fvcom and structured grid finite difference coastal ocean model ecom si respectively the impact of turbulence parameterization was studied by running a coupled npz fvcom system with various vertical turbulence modules implemented in the general ocean turbulence model gotm comparisons were focused on three large tidal dissipation regions georges bank characterized by strong tidal rectification over steep bottom topography and tidal mixing fronts bay of fundy featuring large semidiurnal tidal oscillations due to the gulf scale resonance and nantucket shoals a tidal energy flux convergence zone for the same given tidal forcing and initial physical and biological conditions the ability of a model to accommodate the irregular coastal geometry and steep bottom topography is critical in determining the robustness of the simulated spatial and temporal structure of n and p for the same given external forcing in fvcom turbulence parameterizations have less impact on n and p in mixed regions than in stratified regions in mixed regions both q e and q ql models reproduced the observed vertical mixing intensity since biological variables remained vertically mixed in these regions their structures were little affected by turbulence closure schemes in stratified regions q e models predicted stronger mixing than q ql models which produced more nutrient fluxes over the slope and thus influenced the growth and distribution of p around the tidal mixing front a direct comparison between observed and model predicted turbulence dissipation rates suggests that q e models with a mixing cutoff at richardson number of 1 0 predict more realistic mixing intensity than q ql models in stratified regions on georges bank

the 26 december 2004 sumatra tsunami analysis of tide gauge data from the world ocean part 1 indian ocean and south africa the m w 9 3 megathrust earthquake of december 26 2004 off the northwest coast of sumatra in the indian ocean generated a catastrophic tsunami that was recorded by a large number of tide gauges throughout the world ocean part 1 of our study of this event examines tide gauge measurements from the indian ocean region at sites located from a few hundred to several thousand kilometers from the source area statistical characteristics of the tsunami waves including wave height duration and arrival time are determined along with spectral properties of the tsunami records

the global reach of the 26 december 2004 sumatra tsunami numerical model simulations combined with tide gauge and satellite altimetry data reveal that wave amplitudes directionality and global propagation patterns of the 26 december 2004 sumatra tsunami were primarily determined by the orientation and intensity of the offshore seismic line source and subsequently by the trapping effect of mid ocean ridge topographic waveguides

double jeopardy concurrent arrival of the 2004 sumatra tsunami and storm generated waves on the atlantic coast of the united states and canada 1 a detailed analysis of over one hundred tide gauge records from the atlantic coast of north america reveals that the arrival of the 26 december 2004 sumatra tsunami on this coast coincided with the presence of tsunami like waves being generated by a major storm tracking northward along the eastern seaboard of the united states according to the tide gauge records waves from the two events coalesced along the shores of maine and nova scotia on 27 december where they produced damaging waves with heights in excess of 1 m tsunami waves were identified in almost all outer tide gauges from florida to nova scotia with maximum tsunami heights for the northern regions estimated to be 32 39 cm in the south maximum tsunami wave heights were in the range of 15 to 33 cm

simulation of the development of karst aquifers using a coupled continuum pipe flow model 1 this paper is intended to provide insight into the controlling mechanisms of karst genesis based on an advanced modeling approach covering the characteristic hydraulics in karst systems the dissolution kinetics and the associated temporal decrease in flow resistance karst water hydraulics is strongly governed by the interaction between a highly conductive low storage conduit network and a low conductive high storage rock matrix under variable boundary conditions only if this coupling of flow mechanisms is considered can an appropriate representation of other relevant processes be achieved e g carbonate dissolution transport of dissolved solids and limited groundwater recharge here a parameter study performed with the numerical model carbonate aquifer void evolution cave is presented which allows the simulation of the genesis of karst aquifers during geologic time periods cave integrates several important features relevant for different scenarios of karst evolution 1 the complex hydraulic interplay between flow in the karst conduits and in the small fissures of the rock matrix 2 laminar as well as turbulent flow conditions 3 time dependent and nonuniform recharge to both flow systems 4 the widening of the conduits accounting for appropriate physicochemical relationships governing calcite dissolution kinetics this is achieved by predefining an initial network of karst conduits protoconduits which are allowed to grow according to the amount of aggressive water available due to hydraulic boundary conditions the increase in conduit transmissivity is associated with an increase in conduit diameters while the conductivity of the fissured system is assumed to be constant in time the importance of various parameters controlling karst genesis is demonstrated in a parameter study covering the recharge distribution the upgradient boundary conditions for the conduit system and the hydraulic coupling between the conduit network and the rock matrix in particular it is shown that conduit diameters increase in downgradient or upgradient direction depending on the spatial distribution local versus uniform of the recharge component which directly enters the conduit system

effects of bathymetry on tsunami propagation application of ray tracing to tsunamis ray tracing of seismic surface waves is applied to tsunami propagation to examine bathymetric effect along its propagation path computations are made for trans pacific tsunamis and for near field tsunamis in the japan sea for tsunamis across the pacific ocean the comparison to a uniform ocean shows that focusing and defocusing due to bathymetry are significant for some combinations of source and receiver for example the refraction of rays is predominant at the east pacific rise for the tsunami from chile the tsunamis in the japan sea are strongly affected by the shallow yamato rise the predicted arrival time and amplitude distribution generally agree with the observations from an actual tsunami since the computation can be made very quickly the method is useful for preliminary analysis of tsunami propagation such as in an operational warning system or in the determination of computational area for finite difference computation

waveform and spectral analyses of the 2011 japan tsunami records on tide gauge and dart stations across the pacific ocean we studied the 11 march 2011 tohoku tsunami through analysis of the sea level records from 21 tide gauge and 16 dart deep ocean assessment and reporting of tsunamis stations from across the pacific ocean the extreme power of this trans oceanic tsunami was indicated by the trough to crest heights of 3 03 m at arena cove on the western coast of the usa and 3 94 m at coquimbo on the southern coast of chile the average value of the maximum amplitude was 163 9 cm for the examined tide gauge records at many coastal tide gauge stations the largest wave arrived several hours after the first arrival of the tsunami wave and the tsunami lasted for a long time with an average duration of 4 days on the contrary at most of the dart stations in the deep ocean the first wave was the largest the tsunami amplitudes were smaller with an average maximum of 51 2 cm and the durations were shorter with an average of 2 days the two dominant tsunami periods on the dart records were 37 and 67 4 min which are possibly attributed to the width and length of the tsunami source fault respectively the dimensions of the tsunami source was estimated as 233 km 424 km wavelet analyses of tide gauge and dart records showed that most of the tsunami energy was distributed at the wide period band of around 10 80 min during the first hour after the tsunami arrival then it was concentrated in a relatively narrower band the frequency time plots showed the switches and lapses of tsunami energy at the 35 and 65 min period bands

recent observations of the mean circulation on georges bank abstract a clockwise circulation around georges bank was measured by means of moored current meters aircraft tracked surface drifters and satellite tracked drifters drogued at 10 m the strongest flow was in a narrow jetlike current 30 cm s 1 along the northern flank of the bank the flow of shelf water on the southern flank was westward 10 cm s 1 toward the middle atlantic bight some of this water flowed northward through the eastern side of great south channel and recirculated around georges bank the satellite tracked drifters and the moored observations indicate that the circulation around the bank was not completely closed and considerable variability occurs in the trajectory of an individual water particle

tsunami energy ocean bottom pressure and hydrodynamic force from stochastic bottom displacement tsunami generation and propagation due to a randomly fluctuating of submarine earthquake modeled by vertical time dependent of a stochastic bottom displacement are investigated the increase in oscillations and amplitude in the free surface elevation are controlled by the noise intensity parameter of the stochastic bottom displacement evolution of kinetic and potential energy of the resulting waves by the stochastic bottom displacement is examined exchange between potential and kinetic energy was achieved in the propagation process the dynamic ocean bottom pressure during tsunami generation is investigated as the vertical displacement of the stochastic bottom increases the peak amplitude of the ocean bottom pressure increases through the dynamic effect time series of the maximum tsunami wave amplitude kinetic and potential energy wave and ocean bottom pressure gauges and the hydrodynamic force caused by the stochastic source model under the effect of the water depth of the ocean are investigated

the great tsunami tsunami if that strange word doesn t sound too familiar join the club it s a foreign word coined by the japanese who live uneasily on that pacific rim of fire where all kinds of earth movements are common if a very strong earthquake for example so disrupts the seabed it may on rare occasion thrust the overlying water so sharply upward that a massive sea mount results on the ocean surface then that mountain dissipates in a tidal wave roaring outward in all directions such is a tsunami

slow slip below port blair andaman during the great sumatra andaman earthquake of 26 december 2004 1 although several studies suggest that a slow slip followed the seismic slip on the northern half of the 1300 km long plate interface that ruptured during the great sumatra andaman earthquake the onset and duration of the slow slip remain unresolved in this paper we analyze a tide gauge record at port blair situated about 1000 km north of the epicenter our preferred model which fits the observed data well consists of a mixed mode of slip half of the total slip occurring seismically in less than 5 min after the rupture arrival and the rest developing in the next 30 min a scenario of slow slip on the northern half of the rupture area that is consistent with seismic data and gps data consists of slip on the time scale of 1 hour over the rest