relationships for non darcy flow in rockfill this paper describes a synthesis of various studies on non darcy flow in rockfill material based on pipe theory and taylor s 1948 definition for mean hydraulics radius in rockfill material theoretical relationships between friction coefficient and reynolds number and relationships between hydraulic gradient and bulk seepage velocity have been obtained the new relationships between hydraulic gradient and bulk velocity are then compared to the various formulas for rockfill available in the literature by computer simulation

source parameters and scaling relations for small earthquakes in the matsushiro region southwest honshu japan abstract using near field broadband data from a suite of crustal earthquakes which occurred in a small homogeneous source region we examine the scaling relationships among source parameters for earthquakes in the critical 1 5 to 4 5 magnitude range we take special precautions to insure that our conclusions are not biased by local structure seismic moment fault radius and stress drop relations were determined for 32 small shallow strike slip earthquakes 1 6 m l 4 3 in the matsushiro region of southwest honshu japan spectral and cepstral analyses of short period arrivals exhibit structure interpreted as resulting from reverberations within thin low velocity surface layers below the recording site furthermore calculated crustal transfer functions for sh predict a peak over the range of 2 to 4 hz this type of site response can bias estimates of spectral parameters particularly corner or characteristic frequencies for simple sources such a bias can be reduced by filtering in the cepstral domain the effect of cepstral filtering on corner frequency determinations is generally less than 20 per cent and tends to decrease them particularly for larger events where the structurally induced spectral enhancement is at frequencies above the source related corner frequencies estimates of the seismic moment brune stress drop and fault radius for each event were calculated from sh displacement amplitude spectra the seismic moments range from 10 18 to 10 22 dyne cm the stress drops range from 0 008 to 16 bars the relationship between log stress drop and log moment is approximately linear with a slope of 1 up to a moment of 2 10 21 dyne cm but for higher moments the slope is not significantly different from zero fault radii range from 0 3 to 1 2 km there is a physical scatter in radius for any given moment up to a factor of 1 5 for moments less than 2 10 21 dyne cm there is no significant trend in the radius as a function of moment but for higher moments the radius increases with moment the main conclusion is that the stress drop is the dominant scaling factor for moments less than 10 21 dyne cm for higher moment the source dimension becomes the controlling factor

precursory seismic quiescence before the 1994 kurile earthquake mw 8 3 revealed by three independent seismic catalogs we have found that the m w 8 3 kurile earthquake on october 4 1994 followed an outstanding seismic quiescence starting 5 6 years before the mainshock near the ruptured area we have analyzed three independent seismic catalogs institute of seismology and volcanology hokkaido university isv japan meteorological agency jma and international seismology center isc in spite of selecting different magnitude bands and time windows all three catalogs presented the common feature of the seismic quiescence this fact strongly suggests that the seismic quiescence should not be a man made change but actually occurred moreover we have confirmed that the seismic quiescence was the most significant and the earthquake was the largest in the past twenty five years in this region therefore we confidently interpret this seismic quiescence as an indication of a preparation process for the m w 8 3 kurile earthquake

estimating mean velocity in mountain rivers it is often necessary to estimate the mean velocity in ungaged mountain rivers but the flow resistance equations available for this purpose require further testing and development such rivers are characterized by coarse bed materials steep slopes and low depths for these conditions boulders protrude well into or completely through the flow and bed roughness is said to be large scale recently three equations specifically intended for large scale roughness have been developed to address this problem data from a mountain river were used to test the equations all were prone to errors of the order of 30 the errors were systematic all the equations tending to overestimate mean velocity compared to observed values an investigation of the possible sources of error suggested that sampling error in the knowledge of bed material size was a major source of uncertainty in the predicted velocities but that this and discharge errors could not wholly account for the observed discrepancies boulder shape is not represented in the equations but this was discounted as an important parameter on the basis of a flume study it was concluded that further research is required to produce a reliable process based flow resistance equation for mountain rivers

precursory seismic quiescence a preliminary assessment of the hypothesis numerous cases of precursory seismic quiescence have been reported in recent years some investigators have interpreted these observations as evidence that seismic quiescence is a somewhat reliable precursor to moderate or large earthquakes however because failures of the pattern to predict earthquakes may not in general be reported and because numerous earthquakes are not preceded by quiescence the validity and reliability of the quiescence precursor have not been established

rheology of bimodal crystals suspensions results from analogue experiments and implications for magma ascent 1 the effect of crystal size of bimodal suspensions on rheology of magmas at strain rates between 0 and 1 s 1 is studied suspensions consist of silicon oil and two populations of natural crystals with size 63 125 and 250 500 m mixed in different proportions the total solid fraction of the mixtures is between 0 25 and 0 5 at 0 4 finer coarser and bimodal suspensions display comparable viscosities at 0 4 the viscosity of the bimodal suspensions is larger than that of the unimodal ones the bimodal suspension made mainly of finer crystals shows a stronger increase of viscosity with the addition of finer crystals to a suspension of coarser ones produces a more pronounced increase of viscosity with respect to suspensions of coarse or fine crystals alone and of finer crystals with added coarser ones the bimodal suspensions of coarser crystals develops yield stress at 0 25 the others at 0 4 it is modeled the ascent velocity in a 20 m wide dike of magmas with bimodal and unimodal populations of crystals of different size for 0 4 the crystal size has not effects on the ascent velocity of magmas for 0 4 the velocity of a magma with growing phenocrystals decreases as increases less than that of a magma with forming microlites and more of a magma with microlites and growing phenocrystals a magma with phenocrystals and forming microlites has the lowest ascent velocity

the influence of crystal size distributions on the rheology of magmas new insights from analog experiments this study examines the influence of particle size distributions on the rheology of particle suspensions by using analogue experiments with spherical glass beads in silicone oil as magma equivalent the analyses of 274 individual particle bearing suspensions of varying modality uni bi tri and tetramodality as well as of polymodal suspensions with specific defined skewness and variance are the first data set of its kind and provide important insights in the relationship between the solid particles of a suspension and its rheological behaviour since the relationship between the rheology of particle bearing suspensions and its maximum packing fraction m is well established by several theoretical models the results of the analogue experiments of this study reveal that the polydispersity exerts the largest influence on m consequently the estimation of the polydispersity of a particle size distribution is essential for estimating the viscosity of that given suspension

viscosity of hydrous etna basalt implications for plinian style basaltic eruptions water dissolved in a silicate melt can strongly influence its physical properties and thus magma behavior during crystallization degassing foaming and fragmentation etna is a basaltic volcano whose activity is dominated by effusive eruptions which have long represented a threat to the densely populated surrounding area recently recognition of the products of a plinian eruption 122 b c has raised further issues for hazard assessment at etna and other basaltic volcanoes constraining the behavior of etna magma under conditions relevant to both effusive and explosive hazards requires viscosity data under conditions near the glass transition here we have investigated the viscosity of hydrous etna lava in order to better understand eruptive processes which characterize this volcano the experimental methods which have been used include piston cylinder synthesis of the hydrated melts micropenetration viscometry for low temperature viscosity measurements and near infrared spectroscopy for the evaluation of sample homogeneity and measurements of water content additionally scanning calorimetric determinations were performed to check whether incipient crystallization had occurred sample compositions were determined using electron microprobe analysis and 57fe mossbauer spectroscopy results from this study are compared with previous reports of trachytic phonolitic and model calc alkaline rhyolite hpg8 compositions the viscosity of the basaltic melt dry and wet has been parameterized in terms of temperature and water content via the non arrhenian equation log10 4 643 5 812 44 427 04 h2o t k 499 31 28 74 ln h2o where is the viscosity in pa s h2o is the water content in wt and t is the temperature in kelvin we observe that the viscosity of alkali basalt at more than 0 5 wt h2o is similar to that of an alkaline trachyte agnano monte spina eruption phlegrean fields and much higher than that of a peralkaline phonolite teide tenerife at similar silica contents and nbo t for water contents above 1 5 wt the viscosity of the basalt is similar to that of rhyolitic melts with similar water contents at temperatures ranging from 1 050 to 1 150 c and with water contents between 0 5 and 2 3 wt eruptive conditions the viscosities calculated using the equation defined in this study are 1 in reasonable agreement with those calculated using shaw s model and 2 much lower than those experimentally determined in a previous study however outside these temperature and water content ranges the agreement with shaw s model 1972 breaks down

placed rock as protection against erosion by flow down steep slopes the additional resistance to erosion due to flows down steep slopes that can be achieved by placing rock instead of dumping randomly has been quantified during a large scale flume investigation testing was undertaken for slopes of 0 2 0 3 and 0 4 with two layers of armor overlying a filter consistent with conventional rock protection designs two sizes of sandstone with mean diameters of 76 and 109 mm and basalt with a mean diameter of 94 mm were tested placing rock to achieve maximum bulk density mass per unit in situ volume increased failure flow flow at exposure of the filter by 30 of that achieved with the same type of randomly dumped material but the total armor mass per unit surface area increased by 35 a damage approach to steep erosion protection that is similar to that used for coastal breakwater design is presented an improved method of partition between the aerated flow over as well as flow through both random and placed rock has also been quantified better characterization of aer

air water flows in the presence of staggered and row boulders under macroroughness conditions 1 free surface flow over a rough bed at steep slopes entrains large amounts of air bubbles due to the high interaction between the free surface and the bed materials the assessment of mixed air water flow features in the presence of a three dimensional bed configuration from macroroughness to intermediate roughness conditions can hardly be accomplished with aeration models developed for smooth or stepped bed configurations two phase flow properties were measured over rough bed materials in a setup assembled at the pitlab center at the university of pisa pisa italy coarser protruding materials were incorporated over the rough bed to intensify the aeration in the mixed air water flow flow discharges ranging between 0 02 and 0 09 m2 s and slopes between 0 18 and 0 44 were tested a detailed study of the air water inner layer and flow features over staggered and row coarser material arrangement over the base material was carried out results were compared with literature data on free surface flow over smooth and stepped beds

rigid migration of unzen lava rather than flow abstract we have reassessed the mode of advance of lava erupted in the 1990s from unzen fugen dake volcano in northwestern kyushu japan the apparent viscosity of unzen lava had been estimated to be 0 9 4 2 1010 pa s from the observed lava surface velocity in 1991 using jeffreys model based on the assumption that the lava was a newtonian or bingham fluid in contrast the viscosity of synthetic groundmass glass derived from unzen lava had been measured in the laboratory at expected lava temperatures 780 c 880 c to be 1011 1013 pa s considerably higher than the viscosity based on field observation if the suspension effect of crystals is taken into consideration for groundmass glass several orders of magnitude higher viscosity than observed should be expected for unzen lava to seek the source of the disparity in viscosity estimates we first performed uniaxial compression viscometry on natural unzen lava samples collected in 1991 and thereby confirmed that the lava viscosity was actually higher than determined by field observations and equal to or higher than the fluid solid threshold viscosity 1012 pa s this suggests that the observational viscosity had been underestimated from reanalysis of the lava migration using video and photographs contemporaneous with the field based viscosity estimation we found that the lava behavior was far from that of a fluid apparently the lava lobe lost its fluidity at the flow front and instead advanced rigidly thereby indicating that the application of jeffreys model had incorrectly led us to underestimate viscosity although we used only the 1991 lava samples and image data we infer that rigid migration was common for all exogenous lava lobes during the 1991 1995 activity our comparative study demonstrates that cooled and or degassed lavas could show higher mobility than expected from experiment or model based viscosity apparently this occurs when the frictional force is smaller between lobe base and underlying slope than the viscous resistance inherent in lava

hydrodynamics of steep streams with planar coarse grained beds turbulence flow resistance and implications for sediment transport the hydraulics of steep mountain streams differ from lower gradient rivers due to shallow and rough flows energetic subsurface flow and macro scale form drag from immobile boulders and channel and bed forms heightened flow resistance and reduced sediment transport rates in steep streams are commonly attributed to macro scale form drag however little work has explored steep river hydrodynamics in the absence of complex bed geometries here we present theory for the vertical structure of flow velocity in steep streams with planar rough beds that couples surface and subsurface flow we test it against flume experiments using a bed of fixed cobbles over a wide range of bed slopes 0 4 30 experimental flows have a nearly logarithmic velocity profile far above the bed flow velocity decreases less than logarithmically towards the bed and is non zero at the bed surface velocity profiles match theory derived using a hybrid eddy viscosity model in which the mixing length is a function of height above the bed and bed roughness subsurface flow velocities are large 1 m s and follow a modified darcy brinkman forchheimer relation that accounts for channel slope and shear from overlying surface flow near bed turbulent fluctuations decrease for shallow rough flows and scale with the depth averaged flow velocity rather than bed shear velocity flow resistance for rough planar beds closely matches observations in natural steep streams despite the lack of bed or channel forms in the experiments suggesting that macro scale form drag is smaller than commonly assumed in stress partitioning models for sediment transport

effects of crystal shape and size modality on magma rheology erupting magma often contains crystals over a wide range of sizes and shapes potentially affecting magma viscosity over many orders of magnitude a robust relation between viscosity and the modality of crystal sizes and shapes remains lacking principally because of the dimensional complexity and size of the governing parameter space we have performed a suite of shear viscosity measurements on liquid particle suspensions of dynamical similarity to crystal bearing magma our experiments encompass five suspension types each consisting of unique mixtures of two different particle sizes and shapes the experiments span two orthogonal subspaces of particle concentration as well as particle size and shape for each suspension type thereby providing insight into the topology of parameter space for each suspension type we determined the dry maximum packing fraction and measured shear rates across a range of applied shear stresses the results were fitted using a herschel bulkley model and augment existing predictive capabilities we demonstrate that our results are consistent with previous work including friction based constitutive laws for granular materials we conclude that predictions for ascent rates of crystal rich magmas must take the shear rate dependence of viscosity into account shear rate dependence depends first and foremost on the volume fraction of crystals relative to the maximum packing fraction which in turn depends on crystal size and shape distribution

precursory seismic quiescence seventeen cases of precursory seismic quiescence to mainshocks with magnitudes fromml 4 7 toms 8 0 are summarized the amount of rate decrease ranges from 45 to 90 the significance of these changes varies between 90 and 99 99 the assumption that the background rate is approximately constant is fulfilled in most crustal volumes studied all quiescence anomalies seem to have abrupt beginnings and the rate during the anomalous period is fairly constant the duration of the precursors ranges from 15 to 75 months and it is not clear what factors determine that time at least three successful predictions have been based on seismic quiescence these cases have shown that mainshocks can be predicted based on quiescence but they have also shown that the interpretation of the data in real time is difficult and nonunique if a false alarm is defined as a period of quiescence with a significance level larger than a precursory quiescence in the same tectonic area then we estimate based on searches in four areas that the false alarm rate may be on the order of 50 failure to predict may be expected in perhaps 50 of mainshocks even in carefully monitored areas quiescence cannot be used as a precursor in tectonic environments with low seismic activity most characteristics of the phenomenon are still poorly defined but data exist which probably permit at least a doubling of the presently available data on case histories

ultrafine spherical quartz formation during seismic fault slip natural and experimental evidence and its implications abstract in recent works on the determination of pseudotachylyte within the principal slip zone psz of the chelungpu fault taiwan we demonstrated that frictional melting occurred at shallow depths during the 1999 mw 7 6 chi chi earthquake thus the characteristics of melts are of paramount importance to investigate processes controlling dynamic fault mechanics during seismic slips we conducted rock friction experiments on siltstone recovered from the taiwan chelungpu fault drilling project tcdp at a slip rate of 1 3 m s and a normal stress of 1 mpa here we not only target to characterize experimental pseudotachylyte and evaluate the associated frictional behavior but also compare it with natural frictional melts of tcdp our results show that 1 initial shear stress drop was related to the generation of low viscosity melt patches 2 the evolution of shear stress in the postmelting regime was congruent with frictional melt rheology and 3 the slip strengthening presumably resulted from the extremely low content of water of the frictional melt in particular the state of art of in situ synchrotron analyses x ray diffraction and transmission x ray microscope determine the presence of ultrafine spherical quartz usq grains 10 nm to 50 nm in the glassy matrices presumably produced at high temperature our observations confirm that the usq grains formed in rock friction experiments do occur in natural faults we surmise the usq is the result of frictional melting on siltstone and represents the latest slip zones of the chelungpu fault and further infer that the viscous melts may terminate seismic slips at shallow crustal conditions

seismic quiescence before the urakawa oki earthquake abstract there were significant changes in seismicity preceding a large earthquake the urakawa oki earthquake of 21 march 1982 this event a m jma 7 1 thrust fault crustal earthquake is the largest from a data set of 35 000 earthquakes beneath the southeastern corner of hokkaido island japan during the period july 1976 through december 1986 there was a quiescence for the 2 years preceding the main shock surrounding but not including the immediate epicenter and only for magnitudes 3 during the same time span there was an increase in the number of small magnitudes 2 4 events restricted to the general focal region of the main shock the magnitude dependence of the precursory seismicity patterns is a departure from self similarity one of the currently prevalent assumptions in earthquake source models these seismicity anomalies can be seen using conventional methods such as cumulative number versus time for selected magnitudes in a bounded geographical region however such displays require a priori knowledge or assumptions about the prospective target region and magnitude range for this anomaly there was no reason to target the epicentral region in advance and the usual assumption that quiescence should be most evident at small magnitudes was not appropriate here we have developed an efficient objective procedure for alerting one to the possible existence of a developing anomaly and then analyzing its spatial bounds and its magnitude dependence this procedure has potential value as a general monitoring tool

flow resistance estimation in mountain rivers examination of the flow resistance of high gradient gravel and boulder bed rivers using data collected in british mountain rivers with slopes of 0 4 4 shows that there are differences in resistance variation between mountain and lowland rivers and that between site variations do not necessarily reflect at a site variations comparison of data with the familiar resistance equation relating the dracy weisbach friction factor to the logarithm of relative submergence shows that the equation tends to overestimate the resistance in uniform flow the equation also tends to underestimate the rate of change of resistance at a site as discharge varies with high gradients the influences of nonuniform channel profile sediment size distribution channel slope and sediment transport are reviewed but the data do not allow any quantification of these effects instead an empirical approach based on the available data is presented allowing the friction factor to be calculated from the relative submergence with an error of up to n25 to n35 a summary of the field data is included

rheology of crystal bearing silicate melts an experimental study at high viscosities the viscosity of partially crystallized mg3al2si3o12 melts has been measured under uniaxial compression in the interval 1010 1013 poise as a function of the volume fraction of crystals these inclusions are well rounded spherulites of aluminous enstatite having the same composition as the melt and whose growth rate is negligible at the temperature of the measurements the viscosity increases by less than 1 order of magnitude for crystal fractions of 40 vol and remains newtonian up to the maximum stress exerted namely 1 kbar the einstein roscoe equation 0 1 m n provides very good fits to the measurements only if either the m or n parameter is allowed to depend on temperature for modeling of magmatic processes however the widely recommended constant values m 0 6 and n 2 5 should be adequate the rheology changes abruptly when the clustered spherulites begin to oppose shear deformation at a crystal fraction of about 40 vol the viscosity becomes non newtonian with yield strengths of a few tens of bars at temperatures at which the viscosity of the melt is higher than 1010 poise as long as the crystal fraction remains lower than 70 vol the deformation proceeds in an irregular manner with a nonuniform distribution of crystals and melt the deformation becomes again regular at low stresses with lower melt fractions but samples undergo extensive fracturation along the direction of uniaxial stress similar rheology changes have been observed during the isothermal crystallization of li2si2o5 melts which produces small ellipsoidal inclusions these results suggest that the influence of solid suspensions on the rheology of magmas is primarily determined by the crystal fraction even though additional measurements would be useful to determine the possible influence of other factors such as the size distribution or the shape of the inclusions

magnitude frequency relation for small earthquakes a clue to the origin of ƒmax of large earthquakes in order to test the hyothesis that the max of large earthquakes is due to the source effect and is causally related to the corner frequency of small earthquakes when it becomes constant below magnitude about 3 we constructed the frequency magnitude relation for earthquakes with magnitude range from 1 3 to 4 recorded at a borehole seismograph station operated by the university of southern california at baldwin hills in the middle of the newport inglewood fault a procedure was developed for an accurate estimation of moment magnitude from the measurement of coda amplitude as a function of lapse time the cumulative number of earthquakes per unit time period and area was estimated by finding the detection limit for ts p for each magnitude we found a clear depature of the observed log frequency magnitude relation for m 3 the observed frequency of earthquakes with m 0 5 is almost 10 times less than that expected from the extrapolation of empirical relation for earthquakes with magnitudes larger than 3 we conclude that the observed frequency magnitude relation departs from self similarity for earthquakes with magnitude smaller than about 3 this departure coincides with the widely observed departure of the moment corner frequency relation from self similarity these observations are consistent with the interpretation of max of large earthquakes in terms of the slip weakening instability model in which the critical slip may be a few tenths of a meter to a few meters and the cohesive zone size may be a few hundred meters to a few kilometers

characteristics of the seismic quiescence and activation patterns before the m 7 2 kobe earthquake january 17 1995 abstract we investigated the characteristics of the seismicity changes associated with the m 7 2 kobe japan earthquake january 17 1995 by applying the region time length rtl algorithm to the earthquake catalog of the japan meteorological agency jma the weighted coefficients associated with all three parameters time place and magnitude of earthquakes are taken into account in this algorithm the jma catalog after eliminating aftershocks is complete for events with m 3 in most parts of the japanese islands during 1977 1995 the rtl parameters at the epicenter indicated that a seismic quiescence a decrease of seismicity compared to the preceding background rate started in 1993 and reached its bottom in may 1994 an activation stage an increase of seismicity compared to the preceding background rate with duration of about seven months followed our detailed investigations indicated that the rtl anomaly during 1993 1994 would not be an artificial effect due to the influence of the changes of some threshold parameters or the changes of the jma seismological network the spatial distribution of quiescence during 1993 1994 revealed a significant anomaly in a broad region around the epicenter of the kobe earthquake following the quiescence stage an activation zone which was in order of the rupture length was obtained around the epicenter during may december 1994 the evolutions of spatial distributions of seismic quiescence and activation suggested that above anomalies around the epicentral zone would have reasonable correlation with the preparation of the kobe earthquake the primary characteristics of the seismicity changes prior to the kobe earthquake are similar to those obtained for other large earthquakes in kamchatka and hokkaido therefore the seismicity changes revealed in this study may give better understanding of the seismogenic process of the kobe earthquake and provide useful information for seismic risk estimation

crystal fabric evolution in lava flows results from numerical simulations abstract the analysis of the preferred orientation of crystals crystal fabric in magmatic rocks has become a widely used technique for the reconstruction of the flow history however little is known about the evolution of the fabric during flow here numerical simulations are used to study the fabric evolution of low concentration laminar magmatic flows e g lava flows the fabric evolution of a particle populations with a specified shape cube tablet prism and transitional shape and b crystal populations from a lava flow is analyzed in different flow geometries simple shear hyperbolic and pure shear flows assuming plane strain results show that fabric analysis of the whole crystal population gives little information about flow kinematics whereas the comparative analyses of crystal sub populations with different shapes allow us to recognize the flow geometry simple shear flow produces oscillating to pseudo stable fabrics the fabric strength is lower with respect to that of hyperbolic and pure shear flows and the preferred orientation of crystals does not coincide with the flow direction except for large strain and specified shapes sub fabrics with opposite sense of shear may also develop depending on the crystal shape and finite strain pure shear and hyperbolic flows show stable to pseudo stable fabrics the preferred crystal orientation may or may not coincide with the flow direction according to whether flow is in pure or hyperbolic shear results from numerical simulations are comparable with those from experimental models and natural examples the fabric strength depends on the number of crystals and caution must be used in extrapolating the results beyond the scale of observation the finite strain in a sample from a lava flow from the aeolian islands is determined by the comparative analysis of the calculated and measured fabric parameters fabric intensity and crystal preferred orientation criteria to discriminate among fabrics produced by different flow types are also provided

nonlinear frequency magnitude relationships for the hokkaido corner japan abstract frequency magnitude relationships are determined for a source region defined by a circular epicentral area of 50 km radius centered on the carnegie broadband seismograph at kmu in the southeast corner of hokkaido island japan within this region bounded by a maximum depth of 125 km more than 11 100 earthquakes were detected and cataloged by the hokkaido university network during the period july 1976 through january 1987 the seismicity is divided into two effectively decoupled suites crustal eurasian plate and subduction pacific plate the frequency magnitude recurrence distributions exhibit departures from linearity which are statistically significant below m d 2 5 for the crustal data suite and m d 3 5 for the subduction data suite three independent tests show the nonlinearity is not caused by incompleteness the catalog is complete down to magnitude 2 0 or less for both data suites these observations are therefore inconsistent with the linear gutenberg richter relationship which is assumed to be valid over any magnitude range for which the data are complete there are relatively more large events and fewer small events in the subduction suite the logarithm of the ratio of the number of crustal events to the number of subduction events versus magnitude is monotonically decreasing and remarkably linear over the magnitude range 1 0 to 5 0 this suggests that the observed nonlinearity of these two frequency magnitude relationships has a common origin

self aeration and friction over rock chutes in uniform flow conditions interaction between the free surface and the bed material in flow over rock chutes under macroroughness conditions leads to a high air entrainment into the flow the note reports on an experimental study about air diffusion features in the flow over a long rock chute air concentration profiles and water depths over a uniform bed material were measured an empirical equation for the average air concentration in macroroughness condition for steep slopes is proposed a new darcy weisbach equivalent friction factor for long chutes as a function of the slope and the relative equivalent depth has also been found

discussion of placed rock as protection against erosion by flow down steep slopes by w l peirson j figlus s e pells and r j cox

round shaped riprap stabilization in overtopping flow a series of 26 tests was performed on a riprap layer in which median round shaped stones ranging from 32 3 to 99 1 mm from 1 27 to 3 90 in were subjected to overtopping flow conditions embankment slopes range from 10 to 45 with median stone sizes ranging from 23 9 to 104 2 mm from 0 94 to 4 1 in the database was analyzed yielding a unique expression in which the median size of a round shaped stone can be predicted as a function of the unit discharge embankment slope and coefficient of uniformity it was determined that the requisite round shaped stones range from 5 to 42 larger than angular stones to stabilize the riprap layer for similar flow conditions with unit flows of 0 2 cm s and slopes of 40 the maximum deviation between rounded and angular shaped stone may approach 70 as flow and bed conditions are extrapolated

seismic quiescence before the m 7 1988 spitak earthquake armenia a detailed analysis of the 35 yr of seismicity between 1962 and 1997 using a gridding technique shows that the m7 spitak earthquake of 1988 december 7 was preceded by a quiescence anomaly that started at approximately 1984 0 5 and lasted about 5 0 5 yr up to the main shock this quiescence anomaly had a radius of about 20 3 km estimated from circular areas with 75 per cent rate decrease centred at the point of maximum significance of the anomaly the quiescence was clearly present in the aftershock volume during the 5 yr before the 1988 main shock but its statistically strongest expression was located 30 km nw of the epicentre this anomaly fulfills the association rules between precursory quiescence anomalies and main shocks even for a tight definition and is therefore proposed as a case of precursory quiescence the largest value of the standard deviate z found by random selection of samples by gridding was z 14 for a time window of tw 3 yr using a sample size of n 300 events this makes this anomaly the strongest observed so far and it is the first documented in an environment of continental collision there are no false alarms exceeding in significance the precursor the armenian earthquake catalogue used for this study had 4600 earthquakes with m mmin 2 2 in the area bounded by 39 5 to 42 n 42 5 to 47 e from the point of view of homogeneous reporting this is the best catalogue we have analysed so far the limits of the data used and the density of the grid are dictated by the data and have no influence on the results the choice of free parameters does not influence the results significantly within the following limits 100 n 500 2 tw 7 2 2 mmin 2 8

evidence for aseismic deformation rate changes prior to earthquakes abstractfor ten earthquakes in nonmagmatic settings there are credible published accounts of pre earthquake deformation rate changes lasting hundreds of seconds to more than a decade although most m 7 5 earthquakes have occurred without detectable pre earthquake deformation the detection threshold for aseismic deformation remains high in that aseismic slip with moment equivalent to an m5 earthquake would in most although not all cases have been missed interseismic deformation rates vary without being followed by earthquakes and a strain rate change prior to the 1989 mw6 9 loma prieta california earthquake is shown to be similar in size to many other rate changes that have occurred since that time most examples of pre earthquake aseismic deformation lasting hundreds of seconds or more probably originate adjacent to or downdip of the seismic rupture plane rather than within the zone that undergoes seismic failure

the rheology of crystal bearing basaltic magmas from stromboli and etna abstract our ability to forecast volcanic hazards at active volcanoes stems from our knowledge of parameters affecting eruption dynamics persistent activity displayed by basaltic volcanic systems such as etna and stromboli is governed mainly by the textural evolution and rheological properties of eruptive products here we investigate the high temperature 1131 c

an expanded model and application of the combined effect of crystal size distribution and crystal shape on the relative viscosity of magmas abstract this study examines the combined effect of crystal size distributions csd and crystal shape on the rheology of vesicle free magmatic suspensions and provides the first practical application of an empirical model to estimate the relative effect of crystal content and csd s on the viscosity of magma directly from textural image analysis of natural rock samples in the form of a user friendly texture rheology spreadsheet calculator we extend and apply established relationships between the maximum packing fraction m of a crystal bearing suspension and both its rheological properties and the polydispersity of a csd by using analogue rotational rheometric experiments with glass fibres and glass flakes in silicone oil acting as magma equivalent this study also provides new insights in the relationship between m and the aspect ratio rp of suspended particles

estimation of flow through and over armored slopes models developed for the transient routing of intense rainfall on small armored slopes depend on expressions for flow resistance below and above the surface of the armored layer a series of 52 experiments are conducted in two flumes to collect data on the basic relationships of flow resistance crushed rock of 26 155 mm median diameter is placed on embankments with slopes ranging from 0 01 to 0 2 and subjected to steady flow in the flumes flow through the rock layer is found to be approximately proportional to the rock layer porosity the square root of the slope and the mean diameter of the rock and weakly proportional to the stage the portion of flow through the filter layer generally cannot be neglected flow resistance decreases and conveyance greatly increases when the stage exceeds the depth of the rock layer a model for flow both beneath and above the rock surface on an armored slope is synthesized from formulas developed for flow in rubble dams and darcy weisbach formulas developed for flow

mapping seismic quiescence in california the decrease of microearthquake activity is a controversial possible precursor for mainshock prediction the calculation of seismic quiescence is a convenient tool to quantify this decrease however the actual size of an anomaly significantly depends on the calculation parameters the necessary averaging over space and time acts as 3d lowpass filter the sliding statistics windows introduce highpass behavior and the magnitude threshold shall ensure catalog completeness but also biases the data selection to argue on any claimed anomaly the only conclusive solution would be an exhaustive search over all parameters over an area significantly larger than just the epicenter region and against a test of the null hypothesis qmap is a new mapping approach to process full catalogs that is some twenty years of data for areas of one million km 2 with one fixed set of parameters it utilizes fractil statistics to avoid errors otherwise induced by clusters of aftershock series qmap features two different scaling modes one to display absolute decrease and a second for weighted anomalies by erosion filtering applied to california one can recognize quiescence anomalies of regional scale prior to the coalinga and loma prieta earthquakes but there are more and greater anomalies distributed all along the san andreas fault system without further criteria to understand these patterns the additional anomalies degrade seismic quiescence to an observation with high false alarm rate for earthquake prediction

riprap design for overtopping flow near prototype flume studies were conducted in which riprap protected embankments were subjected to overtopping flows embankment slopes of 1 2 8 10 and 20 were covered with riprap layers with median stone sizes of 1 2 4 5 and or 6 in each riprap layer was tested by slowly increasing the discharge to failure riprap design criteria for overtopping flows were developed for estimating incipient stone movement and riprap layer failure as a function of the unit discharge stone shape median stone size and embankment slope incipient stone movement occurred at approximately 74 of the riprap layer failure unit discharge it was determined that rounded shape stone should be oversized approximately 40 to provide comparable protection of an angular shape stone flow channelization was observed to occur at approximately 88 of the unit discharge at failure a flow concentration factor of approximately 1 to 3 was introduced for sizing stone

precursory seismic quiescence past present and future precursory seismic quiescence has played a major role in most of the succesful earthquake predictions made to date in addition to these successes the number of detailed post mainshock documentations of precursory quiescence is steadily growing these facts suggest that precursory quiescence will play an important role in earthquake prediction programs of the future for this reason it is important to critically evaluate the present state of knowledge concerning this phenomenon the history of observations of precursory seismic quiescence includes work on seismic gaps and seismic preconditions as well as actual studies of temporal quiescence these papers demonstrated the importance of quantitative evaluation of seismicity rates and the benefits of systematic analysis during the early 1980 s the impact of man made effects on seismicity rates was demonstrated for the first time despite progress in catalog understanding the identification and correction of man made seismicity changes remains as the major barrier to earthquake prediction using these data effects of man made changes are apparent in many past studies of seismicity patterns making the results difficult to evaluate recent experience with real time anomalies has demonstrated the necessity of determining the false alarm rates associated with quiescence precursors determination of false alarm rates depends on quantitative definitions of anomalies and statistical evaluations of their significance a number of successful predictions which have been made on the basis of seismic quiescence provide important lessons for present and future work there are many presently unanswered questions regarding seismic quiescence which must be answered before we can determine the reliability of this phenomena as a precursor

spatial temporal variations in seismicity preceding the may 1980 mammoth lakes california earthquakes abstract anomalous temporal variations in the southern part of the sierra nevada great basin boundary zone sngbz from 1977 to 1980 followed a pattern that several authors have identified as precursory to strong earthquakes from january 1977 to september 1978 a general decrease in seismicity was observed in the southern part of the zone followed by a burst of moderate earthquakes from doyle in the northern part of the sngbz to bishop in the south the 1977 to 1979 variations are particularly noteworthy because they occurred over the entire sngbz indicating a regional rather than local cause in the southern part of the zone a magnitude 5 7 shock 25 km northwest of bishop on 4 october 1978 was followed by an earthquake swarm in the mammoth lakes area with peaks in activity during late 1979 and the spring of 1980 the mammoth lakes activity spread gradually to the west during the first year of this sequence apparently involving several northerly trending fracture zones in an area of about 900 km 2 bursts of activity from december 1979 to april 1980 had increasingly dense spatial clustering temporal clustering showed monthly peaks in the spring of 1980 and intense swarming occurred in mid may about 10 days before the largest events in the sequence a search for changes in p wave velocity changes within the sngbz based on recordings of nevada test site explosions at pairs of stations has so far produced negative results

two current seismic quiescences within 40 km of tokyo summary two highly significant seismic quiescence anomalies that started in 1993 0 exist currently within about 40 km of tokyo they are located in central saitama province at 35 99 n 139 56 e and in tokyo bay south of funabashi at 35 59 n l39 94 e the radii of the anomalous volumes are approximately 15 km centred at about 25 and 20 km depth respectively the seismicity rate during the quiescence was less than 10 per cent background rate in both cases the significance of these quiescences measured by the standard deviate z test comparing the rate of the last three years to the backgound rate is higher than for any other rate changes present in the catalogue zmax 7 5 and 7 2 respectively however episodes of highly significant quiescences which could have been interpreted as precursors but were not followed by main shocks also exist in the data set a third seismic quiescence was found to be in progress since 1993 3 0 5 in nw saitama province at 36 18 n 139 22 e it has a radius of 14 km and is less significant than the other two anomalies zmax 6 8 in a polygon that covers the areas of all three quiescences defined above the seismicity rate since 1994 is only 30 per cent of the previous background rate i e 100 earthquakes that would normally have occurred did not this analysis is based on the earthquake catalogue of the national institute for earth science and disaster prevention for the years 1980 1996 2 and mmin 1 0 as well as for the years 1986 2 1996 2 with mmin 0 1 the anomalies are equally clear in the clustered and in the full catalogues to avoid contamination by explosions only nighttime data 19 00 to 7 00 hours local time were used the frequency magnitude distributions in the quiescent volumes at central saitama nw saitama and funabashi have b values of 1 3 1 5 and 1 1 respectively based on the hypothesis that crustal volumes with high b values may not be capable of m6 earthquakes these three quiescent volumes may be ruled out as source volumes for main shocks of these magnitudes using lilt seismic quiescence hypothesis alone it is a reasonable interpretation to suggest that m 6 5 0 5 earthquakes are expected to terminate each of the three quiescences within 1 year 1 year from now with a 50 per cent probability each the interpretation that all three quiet volumes could rupture together in a large earthquake seems less likely however based on the information that the quiescences are located in volumes with b values above the average b 0 8 it can be argued that the three current quiescences are false alarms the fact that these two lines of evidence allow opposing interpretations in these cases shows that neither hypothesis is sufficiently tested thus the quiescence hypothesis is not advanced enough for issuing earthquake predictions nevertheless it is important that scientific tests of prediction scenarios are formulated in real time so we can learn how to modify our hypotheses to make them useful for prediction in the future

seismicity in subduction zones from local and regional network observations the data provided by local and regional seismograph networks are essential for the solution of many problems of subduction zone seismology the capabilities of such networks are limited by the instrumentation currently in common use and the unfavorable source station geometry often imposed by the regional geography nevertheless important contributions have come from the data gathered in many of the earth s subduction zones the accuracy of hypocenter locations based on regional data is affected by the complex velocity structures characteristic of subduction zones but the problems are now well understood examples of numerous studies of the spatial configurations of the seismicity in subduction zones and consequent interpretations of seismogenesis and subduction processes are reviewed studies of the distributions of earthquakes in time and with magnitude for events down to the microearthquake level have the potential for clarifying the earthquake generating processes and possibly a basis for earthquake prediction other uses of local and regional network data have been for investigations of coda s and the identification of asperities in subduction zones

viscosity measurements of subliquidus magmas alkali olivine basalt from the higashi matsuura district southwest japan abstract we carried out viscosity measurements and sampling of a crystal suspension derived from alkali olivine basalt from the matsuura district sw japan at subliquidus temperatures from 1230 c to 1140 c under 1 atm with nno oxygen buffered conditions viscosity increased from 31 to 1235 pa s with a decrease in temperature from 1230 to 1140 c on cooling olivine first appeared at 1210 c followed by plagioclase at 1170 c the crystal content of the sample attained 31 vol at 1140 c plagioclase 22 olivine 9 non newtonian behaviors including thixotropy and shear thinning were pronounced in the presence of tabular plagioclase crystals the cause of such behavior is discussed in relation to shear induced changes in melt crystal textures relative viscosities r s m where s and m are the viscosities of the suspension and the melt respectively were obtained by calculating melt viscosities from the melt composition and temperature at 1 atm using the equation proposed by giordano and dingwell giordano d dingwell d b 2003 non arrhenian multicomponent melt viscosity a model earth and planetary science letters 208 337 349 the obtained relative viscosities are generally consistent with the einstein roscoe relation which represents r for suspensions that contain equant and equigranular crystals even though the crystal suspension analyzed in the present experiments contained tabular plagioclase and granular olivine of various grain sizes this consistency is attributed to the fact that the effect of crystal shape was counterbalanced by the effect of the dispersion of crystal size the applicability of the einstein roscoe equation with respect to crystal shape is discussed on the basis of the present experimental results our experiments and those of sato sato h 2005 viscosity measurement of subliquidus magmas 1707 basalt of fuji volcano journal of mineralogical and petrological sciences 100 133 142 show that the relationship between relative viscosity and crystal fraction is consistent with the einstein roscoe relationship for axial ratios that are smaller than the critical value of 4 6 5 but discrepancies occur for higher ratios

roughness of loose rock riprap on steep slopes a study was conducted to determine the roughness of rock riprap laid on steep slopes tests were conducted in a 1 07 m wide flume and two 2 74 m wide field scale structures using angular riprap with median diameters d50 ranging from 52 to 278 mm and bed slopes s0 ranging from 0 028 to 0 333 m m empirical relationships were developed to predict the manning roughness coefficient as a function of d50 and s0 the darcy weisbach friction factor was predicted as a function of d d84 the relative submergence newly developed equations are applicable for riprap placed on slopes from 2 8 33 roughness coefficients calculated using the developed equations were compared with roughness coefficients calculated using equations developed from observations on natural mountain streams

the yield strength of subliquidus basalts experimental results yield strength is an important property of particle fluid suspensions in basaltic lavas that crystallize during flow emplacement the onset of yield strength may result in threshold transitions in flow behavior and flow surface morphology however yield strength crystallinity relations are poorly known particularly in geologic suspensions where difficulties of experimental and field measurements have limited data acquisition in the subliquidus temperature range here we describe two complementary experimental approaches designed to examine the effect of particle shape on the low shear yield strength of subliquidus basalts the first involves melting cubes of holocrystalline basalt samples with different initial textures to determine the temperature crystallinity at which these samples lose their cubic form these experiments provide information on the minimum crystal volume fractions 0 20 0 35 required to maintain the structual integrity of the cube the second set of experiments uses suspensions of corn syrup and neutrally buoyant particles to isolate the effect of particle shape on yield strength development from these experiments we conclude that the shape is important in determining the volume fraction range over which suspensions exhibit a finite yield strength as anisotropic particles may orient during flow the effect of particle shape will be controlled by the orientation distribution of the constituent particles we find that the so called excluded volume can be used to relate results of experiments on anisotropic particles to those of suspensions of spherical particles recent measurements of yield strength onset in basaltic melts at crystal volume fractions near 0 25 are consistent with our observations that crystal frameworks develop at low to moderate crystal volume fractions when crystals are anisotropic e g plagioclase we further suggest that conditions leading to yield strength onset at low crystallinities include rapid cooling increased crystal anisotropy heterogeneous nucleation which promotes extensive crystal clustering and large cluster anisotropy and static conditions random crystal orientations

flow resistance of rock chutes with protruding boulders steep and short rough channels such as rock chutes are used in river restoration as grade stabilization structures the stability of these channels can be increased using boulders placed over the base material the boulders can be placed with different configurations such as randomly or in rows in each case their presence affects the geometry of the channel and modifies the hydraulic resistance this paper shows the results of tests conducted on rough channels with or without the insertion of protruding boulders the parameters that influence the flow resistance such as slope relative submergence and blocks disposition were systematically investigated to describe the hydraulic behavior of the structure the aim is to define a relationship useful for practical design which relates the flow resistance in terms of both darcy weisbach friction factor and manning coefficient the results were combined with available data for loose rock riprap to determine new experimental relationships

two categories of earthquake precursors physical and tectonic and their roles in intermediate term earthquake prediction i suggest that earthquake precursors can be divided into two major categories physical and tectonic i define physical precursor to be a direct or indirect indication of initiation or progression of an irreversible rupture generating physical process within the preparation zone of a forthcoming earthquake tectonic precursor is defined as a manifestation of tectonic movement which takes place outside the preparation zone of an impending earthquake as a link in a chain of particular local tectonism in each individual area preceding the earthquake most intermediate term short term and immediate precursors of various disciplines within the source regions of main shocks are considered physical ones some precursory crustal deformations around the source regions are however possibly tectonic precursors because they may be caused by episodic plate motions or resultant block movements in the neighboring regions of the fault segments that will break a possible example of this phenomena is the anomalous crustal uplift in the izu peninsula japan before the 1978 izu oshima earthquake ofm s 6 8 some precursory changes in seismicity patterns in wide areas surrounding source regions also seem to be tectonic precursors because they were probably caused by the particular tectonic setting of each region a typical example is a so called doughnut pattern before the 1923 kanto japan earthquake ofm s 8 2 although most studies on earthquake precursors so far seem to regard implicitly all precursory phenomena observed as physical ones the two categories should be distinguished carefully when statistical analysis or physical modeling is carried out based on reported precursory phenomena in active plate boundary zones where a practical strategy for earthquake prediction may well be different from that in intraplate regions tectonic precursors can be powerful additional tools for intermediate term earthquake prediction

shields versus isbash abstractthe shields and the isbash equations for predicting the stability of rocks exposed to a turbulent flow were both proposed in 1936 and since then both equations have been used widely in the analysis of transport thresholds for coarse sediment these two equations were obtained using two very different approaches but as demonstrated in this paper the equation developed by isbash is consistent with the relation formulated by shields for predicting the motion of sediments either in the flume or in the field comparison of the two equations suggests that standard approaches tend to oversize riprap in mountain streams

precursory seismicity changes associated with the nemuro peninsula earthquake january 28 2000 abstract we investigated the characteristics of the precursory seismicity changes associated with the m 6 8 nemuro peninsula earthquake january 28 2000 by applying the rtl region time length algorithm to the earthquake catalogue of the japan meteorological agency jma the rtl parameters at the epicentre indicated that a seismic quiescence started in 1995 and reached its minimum during october 1996 an activation stage with a duration of about eight months followed our detailed investigations indicated that the rtl anomaly around 1996 was not an artificial effect due to the changes of the model parameters the upgrade of the jma seismic network or the process of aftershock elimination the spatial distribution of quiescence in 1996 revealed a significant anomaly in a broad region around the epicentre of the nemuro peninsula earthquake following the quiescence stage an activation zone which was on the order of the rupture length of this earthquake was obtained around the epicentre during october 1996 july 1997 the consistency of the rupture region and the anomalous activation zone that appeared after the seismic quiescence stage may provide useful information for determining the future risk zones this study may strengthen the understanding of the seismogenic process of strong earthquakes

quantitative mapping of a precursory seismic quiescence to the izu oshima 1990 m6 5 earthquake japan a highly significant seismic quiescence with a standard deviate z 10 1 corresponding to a 99 per cent confidence level lasted from 1987 7 up to the 1990 february 20 izu oshima m 6 5 earthquake the quiescent volume had dimensions of 30 km n s and 10 km e w and was centred below 14 km depth within the recently upgraded seismograph network of the earthquake research institute eri this main shock was the only one with a magnitude m 5 8 in the upper 30 km of the crust for which the precursory quiescence hypothesis could be tested within a radius of 50 km and during the observation period 1983 5 1995 9 there were no other 1 5 yr or longer periods of quiescence that were rated z 6 5 in the declustered earthquake catalogue except one that was associated with volcanic activity the total space time covered by alarms including the volcanic one was less than 1 per cent at the z 6 5 level the rarity of highly significant episodes of quiescence and the correlation in space and time suggest that a precursory seismic quiescence started 2 5 yr before the izu oshima 1990 earthquake in its source volume and to the north of it and that it can be recognized with an alarm level of z 6 0 generating no false alarms during the 1 5 yr quiescence window only 10 earthquakes occurred in the quiet volume whereas 50 events were expected based on the rate seen at other times in randomly selected volumes containing 50 100 and 200 events the anomaly scored z 6 1 to 10 1 on the basis of the data from may 1983 to 1995 there is no highly significant quiescence currently present in the izu oshima area

incipient motion of riprap on steep slopes abstractliu s theory of 1957 to estimate the point of incipient motion derived assuming a flat bed slope and uniform flow states that for large particles the movability number defined as the ratio of the shear velocity to the settling velocity is constant data collected from 12 undistorted and unscaled laboratory tests was used to investigate the applicability of the theory on steep riprap slopes the tests indicate that the dimensionless movability number mn is constant for large particle reynold numbers for design purposes the recommended movability number which emerged from this study is 0 18 provided that the steep bed slope is taken into account the energy slope is considered in mn and that the theoretical settling velocity is calculated using an accurate drag coefficient and the d90 sieve size of the riprap

particle size density relationships in pyroclastic deposits inferences for emplacement processes in moving pyroclastic systems particles are sorted as a function of their sizes densities and shapes the analysis of the distribution of these characteristics in particle populations of pyroclastic deposits is a major tool in evaluating properties and regimes of parent transport systems this paper reports a study of size density relationships of component subpopulations from selected quaternary pyroclastic deposits of the latera volcanic complex vulsini italy by means of integrated field and laboratory investigations including grain size and component analyses density measurements and sem crystal morphoscopy three kinds of particle size density relationships characterize the studied deposits as follows 1 a significant correlation of decreasing sizes with increasing component densities exists for direct suspension sedimentation products including plinian fall and pyroclastic surge deposits 2 a wide data dispersion with poor correlation normally occurs for the main zones of deposits from high concentration pyroclastic flows and 3 component subpopulations occur in a narrow size range irrespective of density in granular systems dominated by grain collisions such as traction zones beneath low concentration pyroclastic surges and sheared basal layers of pyroclastic flows the regression coefficients of size density relationships appear as a comparative measure of particle concentration in the parent systems consistent with that inferred from the degree of sorting and abrasion of crystal subpopulations from sequential fragmentation transport analysis of grain size data and quantitative morphoscopy the crystal component becomes less sorted and more abraded as the fit to the size density relationship decreases from plinian fall to pyroclastic surge to pyroclastic flow consistent with increasing particle concentration in the transporting current

effect of glass on the frictional behavior of basalts at seismic slip rates we performed 31 friction experiments on glassy basalts gb and glass free basalts gfb at slip rates up to 6 5 m s 1 and normal stress up to 40 mpa seismic conditions frictional weakening was associated to bulk frictional melting and lubrication the weakening distance dw was about 3 times shorter in gb than in gfb but the steady state friction was systematically higher in gb than in gfb the shorter dw in gb may be explained by the thermal softening occurring at the glass transition temperature tg 500 c which is lower than the bulk melting temperature tm 1250 c of gfb postexperiment microanalyses suggest that the larger crystal fraction measured in gb melts results in the higher steady state friction value compared to the gfb melts the effect of interstitial glass is to facilitate frictional instability and rupture propagation in gb with respect to gfb

design of rock protection to prevent erosion by water flows down steep slopes conventional stability analysis methods for determining rock armor size to protect steep tan 0 1 embankments from erosion due to downslope flow do not predict the correct dependency of armor size on the slope consequently such methods become very conservative discharge factor of safety 8 at high slopes we review published large scale measurements recorded in the literature and show that adequate representation of flow aeration is important as proposed by hartung and scheuerlein in 1970 however the assembled measurements show that the hartung and scheuerlein design method is not conservative the aerated flow equations of hartung and scheuerlein when combined with a correctly formulated stability equation yield good collapse of the available large scale data and a conservative design method

scale amplification of natural debris flows caused by cascading landslide dam failures debris flows are typically caused by natural terrain landslides triggered by intense rainfalls if an incoming mountain torrent collapses a series of landslide dams large debris flows can form in a very short period moreover the torrent can amplify the scale of the debris flow in the flow direction the catastrophic debris flows that occurred in zhouqu china on 8 august 2010 were caused by intense rainfall and the upstream cascading failure of landslide dams along the gullies in the wake of the incident a field study was conducted to better understand the process of cascading landslide dam failures and the formation of debris flows this paper looks at the geomorphic properties of the debris flow gullies estimates the peak flow discharges at different locations using three different methods and analyzes the key modes i e different landslide dam types and their combinations of cascading landslide dam failures and their effect on the scale amplification of debris flows the results show that five key modes in luojiayu gully and two modes in sanyanyu gully accounted for the scale amplification of downstream debris flows in the zhouqu event this study illustrates how the hazardous process of natural debris flows can begin several kilometers upstream as a complex cascade of geomorphic events failure of landslide dams and erosion of the sloping bed can scale to become catastrophic discharges neglecting recognition of these hazardous geomorphic and hydrodynamic processes may result in a high cost

the effect of particle size on the rheology of liquid solid mixtures with application to lava flows results from analogue experiments 1 we investigate the effect of crystal size on the rheology of basaltic magmas by means of a rheometer and suspensions of silicon oil with natural magmatic crystals of variable size from 63 to 0 5 mm and volume fraction from 0 03 to 0 6 at constant finer suspensions display higher viscosities than coarser ones shear thinning flow index n 0 1 0 2 and is more pronounced stronger departure from the newtonian behavior in finer suspensions maximum packing and average crystal size displays a nonlinear positive correlation while yield stress develops at 0 2 0 3 irrespective of the crystal size we incorporate our results into physical models for flow of lava and show that with respect to lava flows containing coarser crystals those with smaller crystals are expected to 1 flow at lower velocity 2 have a lower velocity gradient and 3 be more prone to develop a region of plug flow our experimental results explain the observation that phenocryst bearing and microlite bearing lavas at etna volcano italy show smooth pahoehoe and rough aa surfaces respectively

an experiment in earthquake prediction and the 7 may 1986 andreanof islands earthquake abstract the occurrence of the 7 may 1986 andreanof islands earthquake provides the opportunity to evaluate the earthquake forecast and specific prediction that had been formulated and promulgated starting more than 2 yr before the prediction experiment was based on the observation of seismic quiescence in the part of the aleutian subduction zone monitored by the central aleutians adak seismic network the magnitude estimate m s 7 to 7 5 was based on the size of the quiescent zone and the seismic history of the adak region since 1900 the time of occurrence was predicted as a test of the discovery by habermann of a quiescence lasting about 3 yr prior to the 2 may 1971 adak canyon event and the hypothesis that a characteristic precursor time is a valid concept the place was originally forecast as near adak island then specified with epicenter at the eastern margin of adak canyon rupturing to the west under the canyon the 7 may 1986 earthquake had magnitude m s 7 7 m w 8 0 with epicenter 140 km east of the predicted place rupturing east of adak canyon and stopping in the area predicted as the nucleation point the time of this event was 6 months later than predicted thus the specifically predicted event has not happened the largest part of the rupture did go through the segment that had been most active before the onset of quiescence and which experienced the sharpest and most persistent quiescence a cause and effect relation between preparation for this earthquake and the quiescence is still to be firmly established but the distribution of the pattern of quiescence relative to the epicentral location and the site of the greatest moment release suggest a physical connection between earthquake and seismicity patterns the predictions of location and time were acknowledged throughout as highly speculative no firm basis exists for quantitative estimation of the uncertainties to be assigned to the elements of an intermediate term prediction this experiment lends support to the validity of quiescence as a precursor at least for some earthquakes and demonstrates the need for local network data to provide the high resolution of seismicity required for prediction efforts based on seismicity patterns

shear rate dependence of the pāhoehoe to a ā transition analog experiments hawaiian lava flows typically erupt as pahoehoe and transform to a aas they travel away from eruptive vents although the exact conditions that govern this transformation are not well constrained here we describe a set of laboratory experiments that use corn syrup and ellipsoidal rice grains as an analog to lava with crystals to examine the depen dence of the transition on shear rate and particle concentration at a particle volume fraction of 0 3 increasing the shear rate produces a sequence of deformation regimes defined by increasing amounts of shear localization the same regimes may be traversed at constant shear rate by varying the particle concentration at high shear rates the onset of nonlaminar deformation corresponds to the percolation threshold thus providing a link between suspension microstructure and deformation behavior together these results high light the combined importance of shear rate and crystallinity in determining the flow behavior of basaltic lava

occurrence of a predicted earthquake on the san andreas fault in may 1985 we predicted1 that an earthquake would occur on the san andreas fault near stone canyon california within a year the prediction was based on the observation of seismic quiescence defined as a significant decrease in the average occurrence rate of earthquakes within the source volume of the future mainshock a mainshock of magnitude ml 4 6 occurred on 31 may 1986 rupturing exactly the specified segment of the fault this is the first successful prediction of an earthquake along the san andreas fault and the probability to have come true by chance is 5 although the prediction addressed only a small main shock its success was significant because the location size and occurrence time were correctly specified for an earthquake in a populated area larger earthquakes will undoubtedly be successfully predicted by the same method in the future but the major segments of the san andreas fault near san francisco and los angeles have such a low background seismicity rate that the method will probably not be applicable there

teleseismic detection in the aleutian island arc recently it has become apparent that teleseismic detection has decreased substantially in many regions of the world the major decrease was related to the closure of the vela arrays in the united states during the late 1960 s this detection decrease has been recognized in south and central america mexico the kuriles the caribbean tonga and the new hebrides in this paper the effect of the closure of these arrays on the reporting of events in the aleutian island arc is examined in the aleutians the detection history is complicated by the short term installation of a local network on and near amchitka island during the early 1970 s the temporal coincidence of the installation of this network and the closure of the vela arrays delayed the detection decrease in the central aleutians until the amchitka network was closed in early 1973 reporting in the eastern aleutians was unaffected by the installation of the amchitka network in that region the detection decreased between 1968 and 1970 the time of the closure of the vela arrays new techniques have been developed which make it possible to determine the effect of station installation or closure on the reporting in some regions these techniques rely on plots which show the distribution of an observed seismicity rate change in the magnitude domain these plots make it possible to recognize probable detection changes and to determine quantitatively magnitude cutoffs which avoid these changes the magnitude level at which these cutoffs are made is termed the minimum magnitude of homogeneity mmin h the reporting of events with mb 4 6 in the aleutians decreased substantially during the mid 1970 s so mmin h in this region is 4 7 this is different from the magnitude of completeness mmin c which is mb 5 0 0 1 if one is interested in examining seismicity rates for changes which may be precursors to earthquakes then awareness of detection related changes and magnitude cutoffs which avoid these changes are essential for meaningful results

strombolian eruptions and dynamics of magma degassing at yasur volcano vanuatu abstract open vent basaltic volcanoes account for a substantial portion of the global atmospheric outgassing flux largely through passive degassing and mild explosive activity we present volcanic gas flux and composition data from yasur volcano vanuatu collected in july 2018 the average volcanic plume chemistry is characterised by a mean molar co2 so2 ratio of 2 14 h2o so2 of 148 and so2 hcl of 1 02 the measured mean so2 flux in the period of 6th to 9th july is 4 9 kg s 1 therefore the mean fluxes of the other species are 7 5 kg s 1 co2 208 kg s 1 h2o and 4 8 kg s 1 hcl the degassing regime at yasur volcano ranges from passive to active styles with the latter including strombolian activity and spattering gases emitted during active degassing are enriched in so2 over hcl and co2 over so2 relative to passive degassing with co2 so2 ratios of 2 85 0 17 so2 hcl of 1 6 0 22 and h2o so2 of 315 78 8 gases emitted during passive degassing have co2 so2 ratios of 1 96 0 12 so2 hcl of 0 50 0 07 and h2o so2 of 174 43 5 we use a model of volatile degassing derived from melt inclusion studies metrich et al 2011 combined with our observations of chemical variations in the outgassing bubbles to propose a mechanism for magma degassing in the conduit at yasur we envisage a shallow conduit filled with crystal rich magma forming a viscous and mobile plug that develops an effective yield strength from the surface to a depth of at least 2000 m in which bubbles are trapped grow ascend towards the surface and burst in a typical strombolian eruption deeper bubbles released during active degassing are enriched in co2 and so2 compared to bubbles released during passive degassing which are sourced from close to the surface and are consequently hcl rich

rheology of magmas with bimodal crystal size and shape distributions insights from analog experiments 1 magmas in volcanic conduits commonly contain microlites in association with preexisting phenocrysts as often indicated by volcanic rock textures in this study we present two different experiments that investigate the flow behavior of these bidisperse systems in the first experiments rotational rheometric methods are used to determine the rheology of monodisperse and polydisperse suspensions consisting of smaller prolate particles microlites and larger equant particles phenocrysts in a bubble free newtonian liquid silicate melt our data show that increasing the relative proportion of prolate microlites to equant phenocrysts in a magma at constant total particle content can increase the relative viscosity by up to three orders of magnitude consequently the rheological effect of particles in magmas cannot be modeled by assuming a monodisperse population of particles we propose a new model that uses interpolated parameters based on the relative proportions of small and large particles and produces a considerably improved fit to the data than earlier models in a second series of experiments we investigate the textures produced by shearing bimodal suspensions in gradually solidifying epoxy resin in a concentric cylinder setup the resulting textures show the prolate particles are aligned with the flow lines and spherical particles are found in well organized strings with sphere depleted shear bands in high shear regions these observations may explain the measured variation in the shear thinning and yield stress behavior with increasing solid fraction and particle aspect ratio the implications for magma flow are discussed and rheological results and textural observations are compared with observations on natural samples

potential causes for the non newtonian rheology of crystal bearing magmas experimental studies indicate that crystal bearing magma exhibits non newtonian behavior at high strain rates and solid fractions we use a zero dimensional 0 d inversion model to reevaluate rheological parameters and shear heating effects from laboratory data on crystal bearing magma the results indicate non newtonian behavior with power law coefficients of up to n 13 5 it has been speculated that finite strain effects shear heating power law melt rheology or plasticity are responsible for this non newtonian behavior we use 2 d direct numerical crystal scale simulations to study the relative importance of these mechanisms these simulations demonstrate that shear heating has little effect on aggregate bulk rheologies finite strain effects result in both strain weakening and hardening but the resulting power law coefficient is modest maximum n 1 3 for simulations with spherical crystals the strain weakening and hardening behavior is related to rearrangement of crystals rather than strain rate related weakening finite strain effects were insignificant in a numerical simulation with naturally shaped crystals strain partitioning into the melt phase may induce microscopic stresses that are adequate to provoke a nonlinear viscous response in the melt large differential stresses and low effective stresses revealed by the simulations are sufficient to cause crystals to fail plastically numerical experiments that account for plastic failure show large power law coefficients n 50 in some simulations we conclude that this effect is the dominant cause of the strong nonlinear viscous response of crystal bearing magmas observed in laboratory experiments

effect of mechanical interactions on the development of shape preferred orientations a two dimensional experimental approach abstract modifications in the development of preferred orientations of rigid particles due to mechanical interactions between particles are studied experimentally in two dimensions experiments in both pure shear and simple shear were performed and the results analysed using an easy and fast new automatic method for increased concentration of rigid particles the rotation of individual particles may be slowed down or even stopped due to collisions or disturbance of the flow in the matrix caused by neighbours in coaxial flow the fabric intensity is consequently reduced in simple shear flow the fabric evolution is no longer cyclic the intensity is on average weaker and the fabric axis rotates asymptotically toward the shear plane in the case of preferred orientations of particles having a low aspect ratio 2 5 the fabric rotates through the shear plane then undergoes a reverse rotation and rotates toward the shear plane again in the light of these experimental results we emphasize that quantification of finite strain based on such fabrics may lead to significant underestimates and calculated values should be taken as minimum estimates the kinematic significance of concentrated rigid particle preferred orientations in rocks is modified by interactions between particles techniques for qualitative or quantitative kinematic analysis may become unreliable for simple shear flows the concentrated population fabrics show an angular behaviour close to that of passive markers they tend to align parallel to the shear plane in simple shear flow