the importance of hydrothermal venting to water column secondary production in the northeast pacific abstract the purpose of this study is to show that seafloor hydrothermal venting in the open northeast pacific ocean has a marked impact on secondary biomass and production within the overlying water column specifically we use net tows and concurrently measured acoustic backscatter data collected over six summers to examine the effects of hydrothermal venting from the endeavour segment of juan de fuca ridge on macro zooplankton biomass and production throughout the entire 2000 m depth range previous research shows that ontogenetic diapausing migrators and their predators from the upper ocean aggregate above the neutrally buoyant plumes in summer and resume feeding on plume and bottom upwelled particles resulting in increased zooplankton reproductive output to the upper ocean within the limitations of our sampling methodology net tows reveal a statistically significant exponential decline in total water column biomass with increasing lateral distance from the vent fields the acoustic backscatter data show a similar decline but only below 800 m depth near surface biomass was highly variable throughout the region but values near vents consistently ranged higher than summer values found elsewhere in the offshore northeast pacific water column biomass was similar in magnitude above and below 800 m depth throughout the region because epiplume biomass can be advected a considerable distance from vent fields biomass enhancement of the water column from hydrothermal venting may extend considerable distances to the west and northwest of the vent sites in the prevailing directions of the subsurface flow based on the extensive acoustic doppler current profiler adcp data collected and the strong correlation between zooplankton production derived from net sample biomass and acoustic backscatter intensity we estimate that daily macro zooplankton production in the upper 400 m of the water column within 10 km of the vent fields averages approximately 16 of photosynthetic primary production the z ratio whereas the total water column zooplankton production averages 26 of surface primary production local grazing rate estimates metabolic constraints and other open ocean studies suggest that the z ratio should be no higher than 5 which it is at off axis background sites in the study region this finding indicates that nutrient sources other than upper ocean primary production fuel both upper and deep ocean zooplankton biomass and growth near the endeavour ridge hydrothermal vents

the density distributions and the correlations of an earthquake s source parameters the data analysis of the source parameters of five sets of earthquake sequences aftershocks and earthquakes scattered in a region shows that the scalar seismic moment is correlated with the linear size of the fault and the static stress drop we tentatively imply that a correlation also exists between the radius of the faults and the static stress drops and it is suggested that the static stress drop may be decreasing with increasing radius of the source it is shown that the density distribution of the source radius calculated through the source rupture duration obtained from the body wave pulse boatwright 1980 using the time t between the p wave onset and the first zero crossing on the seismogram may be represented by a power law as the density distribution of the stress drops and of the moment which are also computed it is also suggested and tentatively verified that the density distribution of the areas of the broken barriers on the faults is similar to that of the density distribution of the static stress drops it is finally suggested that the seismicity of a region may be studied two dimensionally as a function of the stress drop and the radius of the source instead of the classic b and b0 values concerning the discussion on the range of the values of the static stress drop whether it is almost constant in a seismic region and varies only from one region to another it is seen that in the aftershocks of the 1994 northridge earthquake it covers a range of almost 5 orders of magnitudes finally it is ascertained that the density distribution of the source parameters does not give equipartition of seismic moment release

age of emplacement of massif type anorthosites in the eastern ghats belt india constraints from u pb zircon dating and structural studies abstract massif type anorthosites in the proterozoic eastern ghats belt of india occur as complexes of varying size within a strongly deformed high to ultra high grade assemblage of metasedimentary and metaigneous rocks recently discovered dikes and sheets of exceptionally hfse and ree enriched ferrodiorites at the immediate contacts of three anorthosite complexes chilka lake bolangir and turkel contain ubiquitous magmatic zircon suitable for u pb dating due to the coeval and comagmatic nature of the ferrodiorites the u pb zircon data provide reliable constraints on the time of anorthosite emplacement zircons from three ferrodiorite samples were analysed applying the conventional multi grain isotope dilution method zircon grains in the bolangir ferrodiorites d4 and b2012 are long prismatic and show the faint fine scale oscillatory zoning typical for magmatic crystallisation with some poorly luminescent thin overgrowths of metamorphic origin the data points obtained for abraded grain fractions are slightly discordant and yield an upper intercept age of 933 32 ma with a lower intercept at 515 20 ma defined by previously published concordant u pb titanite data from calc silicate rocks of the border zone of the anorthosite zircon grains in the chilka lake ferrodiorite ok 76 2 are prismatic and show zoned igneous interiors that are overgrown by irregular poorly luminescent rims presumably of metamorphic origin the u pb ages obtained for abraded grain fractions are concordant and define an age of 792 2 ma the u pb zircon ages for the chilka lake and bolangir ferrodiorites disprove the often quoted mesoproterozoic age of anorthosite emplacement in the egb which was based on a four point rb sr whole rock isochron for the chilka lake anorthosite complex 1404 89 ma sarkar et al 1981 combined with field and geochemical evidence the new u pb zircon ages indicate that the data array in the rb sr evolution diagram should be interpreted as a mixing line resulting from marginal contamination of the ascending hot anorthosite pluton with felsic melts generated in its thermal aureole the u pb zircon ages provide new insights in the deformation history of the eastern ghats belt as structural studies indicate intrusion of the bolangir anorthosite while its country rocks underwent a thrust shear dominated deformation in contrast emplacement of the considerably younger chilka lake anorthosite occurred previous to or at the beginning of a regionally intense transpressive deformation

trace element characteristics ree patterns and partition coefficients of zircons from different geological environments a case study on indian zircons abstract twelve zircon separates from diverse geological settings in peninsular india have been analyzed for their zr hf sc ree th and u contents employing neutron activation techniques the whole rock samples of acid charnockite and a related rock of syenitic composition were also analyzed for these elements after separation of zircons the study reveals that 1 a the zircons exhibit a wide range of variation in elemental abudances and their ratios 2 b their chondritic normalised ree patterns exhibit negative or positive ce and negative eu anomalies in addition to smooth hree enriched patterns without anomalies and 3 c there are significant differences in the ree partition coefficients of zircons from the charnockite and the associated syenite the overall elemental abundances and ree patterns of the zircons could be explained in terms of crystallochemical factors bulk compositional differences of parent melts and paragenetic histories

blue and fin whale call source levels and propagation range in the southern ocean blue balaenoptera musculus and fin whales b physalus produce high intensity low frequency calls which probably function for communication during mating and feeding the source levels of blue and fin whale calls off the western antarctic peninsula were calculated using recordings made with calibrated bottom moored hydrophones blue whales were located up to a range of 200km using hyperbolic localization and time difference of arrival the distance to fin whales estimated using multipath arrivals of their calls was up to 56km the error in range measurements was 3 8km using hyperbolic localization and 3 4km using multipath arrivals both species produced high intensity calls the average blue whale call source level was 189 3db re 1 pa 1m over 25 29hz and the average fin whale call source level was 189 4db re 1 pa 1m over 15 28hz blue and fin whale populations in the southern ocean have remained at low numbers for decades since they became protected using source level and detection range from

rupture process of the 2002 mw 7 9 denali earthquake alaska using a newly devised hybrid blind deconvolution method this paper investigates the kinematics of the rupture process of the main event of the mw 7 9 denali alaska earthquake of 3 november 2002 a newly devised hybrid blind deconvolution method is applied to deconvolve teleseismic broadband s wave displacement recordings of the earthquake so as to determine the apparent source time functions astfs at 10 stations located around the epicenter the derived azimuthal angle of slip strongly indicates that the event ruptured unilaterally in an east southeasterly direction as determined by the calculated astfs the total duration of the rupture process was about 74 sec based on the images of the static slip dis tribution three slip concentrated areas were located at depths of less than 10 km maximum slip was about 13 4 m centered at 170 km east of the hypocenter and the average slip on the observed rupture area reached 4 1 m one concentrated rupture velocity area located at 160 180 km east of the hypocenter coincided with a slip concentrated area of maximum slip amplitude strongly suggesting that seismic energy was released rapidly a region of the fault along the strike direction with high rupture velocity 80 120 km also had very low levels of slip indicating that this portion of the fault may well have been relatively weak maximum and minimum rupture velo cities were respectively 3 32 and 2 64 km sec while the average rupture velocity was about 2 95 km sec based on the average rupture velocity and the source duration it is suggested that the principal rupture length of the denali fault must have been greater than 210 km

low frequency whale and seismic airgun sounds recorded in the mid atlantic ocean beginning in february 1999 an array of six autonomous hydrophones was moored near the mid atlantic ridge 35 n 15 n 50 w 33 w two years of data were reviewed for whale vocalizations by visually examining spectrograms four distinct sounds were detected that are believed to be of biological origin 1 a two part low frequency moan at roughly 18 hz lasting 25 s which has previously been attributed to blue whales balaenoptera musculus 2 series of short pulses approximately 18 s apart centered at 22 hz which are likely produced by fin whales b physalus 3 series of short pulsive sounds at 30 hz and above and approximately 1 s apart that resemble sounds attributed to minke whales b acutorostrata and 4 downswept pulsive sounds above 30 hz that are likely from baleen whales vocalizations were detected most often in the winter and blue and fin whale sounds were detected most often on the northern hydrophones sounds from seismic airguns were recorded frequently particularly during

lu hf and u pb isotope systematics of zircons from the storgangen intrusion rogaland intrusive complex sw norway implications for the composition and evolution of precambrian lower crust in the baltic shield abstract the storgangen orebody is a concordantly layered sill like body of ilmenite rich norite intruding anorthosites of the rogaland intrusive complex ric sw norway 17 zircon grains were separated from ca 5 kg of sand size flotation waste collected from the on site repository from ilmenite mining these zircons were analysed for major and trace elements by electron microprobe and for u pb and lu hf isotopes by laser ablation microprobe plasma source mass spectrometry eight of the zircons define a well constrained mswd 0 37 concordant population with an age of 949 7 ma which is significantly older than the 920 930 ma ages previously reported for zircon inclusions in orthopyroxene megacrysts from the ric the remaining zircons interpreted as inherited grains show a range of 207pb 206pb ages up to 1407 14 ma with an upper intercept age at ca 1520 ma the concordant zircons have similar trace element patterns and a mean initial hf isotope composition of 176hf 177hf949 ma 0 28223 5 ehf 2 2 this is similar to the hf isotope composition of zircons in a range of post tectonic sveconorwegian granites from south norway and slightly more radiogenic than expected for mid proterozoic juvenile crust the older inherited zircons show lu hf crustal residence ages in the range 1 85 2 04 ga one undated zircon plots well within the field of hf isotope evolution of paleoproterozoic rocks of the baltic shield these findings indicate the presence of paleoproterozoic components in the deep crust of the rogaland area but do not demonstrate that such rocks or a sveconorwegian mantle derived component contributed significantly to the petrogenesis of the ric if the parent magma was derived from a homogeneous lower crustal mafic granulite source the lower crustal protolith must be at least 1 5 ga old and it must have an elevated rb sr ratio this component would be indistinguishable in sr nd and hf isotopes from some intermediate mixtures between sveconorwegian mantle and paleoprotoerzoic felsic crust but it cannot account for the initial 143nd 144nd of the most primitive late sveconorwegian granite in the region without the addition of mantle derived material

geology petrology and isotope geochemistry of massif type anorthosites from southwest madagascar four massif type anorthosite bodies 25 100 km2 in area occur within high pressure granulite facies supracrustal gneisses in southwestern madagascar two of these bodies ankafotia and saririaky appear to have been pulled apart by 40 km in a ductile shear zone but structural features such as sub vertical stretching lineations indicate an origin by intense west directed flattening and pure shear country rocks graphite series include abundant graphite schist some with 60 graphite marble quartzite and minor amphibolite and leucogneiss comagmatic granitoids e g charnockites are conspicuously absent the anorthosite bodies are dominated by coarse grained anorthosites and leuconorites feldspars typically 3 5 cm up to 1 m minor norites and oxide rich ferrogabbros occur near the margins but ultramafic rocks are absent typical mineralogy of the anorthositic rocks is plagioclase an41 54 orthopyroxene en38 66 augite mg 32 68 ilmenite magnetite apatite high alumina to 6 1 wt al2o3 orthopyroxene megacrysts are widespread most have exsolutions of calcic plagioclase an72 85 but some contain garnet lamellae metamorphism has produced abundant recrystallization and sporadic coronitic garnet mg 12 36 clinopyroxene assemblages rb sr isotopic analyses of whole rocks and minerals reveal no meaningful age relationships the age of late neoproterozoic metamorphism is best constrained at 559 50 ma by a 6 point sm nd mineral isochron whole rock plag pyx ilm apat gar from a saririaky oxide rich gabbro the igneous crystallization age of the anorthosites is estimated at 660 60 ma by a 19 point combined whole rock and mineral sm nd isochron for samples from both the ankafotia and saririaky bodies initial isotopic ratios calculated at 0 66 ga among 13 whole rocks are nd 2 6 to 5 2 mean 3 7 and isr 0 70328 0 70407 mean 0 70347 indicating derivation of the malagasy anorthosites from a depleted mantle source and little if any contamination with archean crustal material one anorthosite sample with nd 1 4 and isr 0 70344 calculated at 0 66 ga probably reflects the effects of assimilation of early to middle proterozoic crustal basement but typical surrounding graphite schist nd 0 3 isr 0 70636 both at 0 66 ga tdm 1131 ma represents only a minor potential contaminant for the anorthosite bodies tdm model ages of the malagasy anorthosites 797 1280 ma mean of 14 samples 949 ma as those of most other massif type anorthosites are older than the true crystallization age because of crustal contamination effects our isotopic data together with recent u pb data from the anorthosites and surrounding country rocks are consistent with emplacement of the malagasy anorthosite bodies at or before the start of a protracted high grade metamorphic event or series of events between about 630 and 550 ma this period coincides with the collision between and amalgamation of east and west gondwana

preliminary results from vertical seismic profiling of oroville microearthquake s waves seismograms recorded along a 0 5 km deep borehole in oroville ca show that ground level s wave velocity spectra at this location are a product of site effects in the 6 25 to 50 hz range studied both the cleveland hill fault through which the borehole was drilled and the rock above it contribute to a substantial loss of s wave energy in first order approximation the average apparent s wave quality factor qsa along the well is 9 across the fault zone the qsa drops to a low of 3 downhole the seismograms can readily be separated into longitudinal and transverse components particle motion diagrams show that the s arrival is made up of two differently polarized waves this splitting is possibly an effect of wave propagation in the highly cracked and probably anisotropic rock of the region

a single station method for the detection classification and location of fin whale calls using ocean bottom seismic stations passive seismic monitoring in the oceans uses long term deployments of ocean bottom seismometers obss an obs usually records the three components of ground motion and pressure typically at 100 hz this makes the obs an ideal tool to investigate fin and blue whales that vocalize at frequencies below 45 hz previous applications of obs data to locate whale calls have relied on single channel analyses that disregard the information that is conveyed by the horizontal seismic channels recently harris matias thomas harwood and geissler j acoust soc am 134 3522 3535 2013 presented a method that used all four channels recorded by one obs to derive the range and azimuth of fin whale calls in this work the detection classification and ranging of calls using this four channel method were further investigated focusing on methods to increase the accuracy of range estimates to direct path arrivals corrections to account for the influences of the sound speed in the water layer and the velocity structure in the top strata of the seabed were considered the single station method discussed here is best implemented when obss have been deployed in deep water on top of seabed strata with low p wave velocity these conditions maximize the ability to detect and estimate ranges to fin whale calls

quantifying the interaction of an ocean bottom seismometer with the seabed a theory is presented for the coupling between an ocean bottom seismometer obs the sediments upon which it rests and the surrounding water assuming that rotational and tilt effects are negligible or have been made negligible through instrument design the response of the obs to forced harmonic motion is considered in both horizontal and vertical directions under these conditions it is concluded that the measured ratio of velocities when the obs is on the seabed and when it is freely suspended in water for an identical force completely characterizes the obs seabed interaction this enables the velocity transfer functions to be directly calculated without recourse to a detailed model of sediment structure interaction an obs was designed and constructed with good coupling to seabed motion and reduction of rocking effects as principal design criteria including an onboard shaker to conduct in situ coupling experiments the amplitude and phase of coupling data collected on a clay seabed provide transfer functions due to horizontal and vertical seabed motion and horizontal water motion in addition a simple mass spring dashpot model of obs seabed interaction permits the analysis of amplitude only coupling data good vertical coupling can be achieved over a wide bandwidth by designing the sensor package to have a large hydrodynamic added mass in the vertical good coupling to horizontal seabed motion is more difficult to achieve but is possible within a limited bandwidth even on very soft seabeds finally an example of seismoacoustic noise is presented hydrophone signals are compared with horizontal geophone signals received from sources within the ocean and within the seabed and the differences are explained in terms of the coupling transfer functions

microseismicity linked to gas migration and leakage on the western svalbard shelf the continental margin off prins karls forland western svalbard is characterized by widespread natural gas seepage into the water column at and upslope of the gas hydrate stability zone we deployed an ocean bottom seismometer integrated into the masox monitoring arctic seafloor ocean exchange automated seabed observatory at the pinch out of this zone at 389 m water depth to investigate passive seismicity over a continuous 297 day period from 13 october 2010 an automated triggering algorithm was applied to detect over 220 000 short duration events sdes defined as having a duration of less than 1 s the analysis reveals two different types of sdes each with a distinctive characteristic seismic signature we infer that the first type consists of vocal signals generated by moving mammals likely finback whales the second type corresponds to signals with a source within a few hundred meters of the seismometer either due east or west that vary on short tens of days and seasonal time scales based on evidence of prevalent seafloor seepage and subseafloor gas accumulations we hypothesize that the second type of sdes is related to subseafloor fluid migration and gas seepage furthermore we postulate that the observed temporal variations in microseismicity are driven by transient fluid release and due to the dynamics of thermally forced seasonal gas hydrate decomposition our analysis presents a novel technique for monitoring the duration intensity and periodicity of fluid migration and seepage at the seabed and can help elucidate the environmental controls on gas hydrate decomposition and release

near surface attenuation and site effects from comparison of surface and deep borehole recordings abstract near surface attenuation and site effects are investigated using the seismograms of 17 local earthquakes recorded at depths of 0 0 3 1 5 2 5 and 2 9 km in the cajon pass borehole southern california the borehole penetrates 500 m of miocene sandstone and then crystalline granitic basement rock previous estimates of site response have been limited to shallower holes where the surface reflection interferes with the upgoing direct wave and the deepest sensor is not below the severe near surface effects in bedrock spectral ratios of the direct p and s waves for each earthquake between the different recording levels are well modeled with frequency independent q and amplification at the borehole q p 27 8 and q s 21 7 in the upper 2 9 km increasing from q p 26 and q s 15 in the upper 300 m to q p 133 and q s 47 between 1 5 and 3 km one event was also recorded at a surface granite site less than 1 5 km from the wellhead comparison of the 2 9 km recording with that at this granite site gives q p 50 and q s 23 the similarity of these values with those of previous studies at a wide range of sites suggests that q is very low in the near surface independent of rock type near surface amplification appears considerably more site dependent at the wellhead the amplifications at 1 hz of the direct p and s waves are 12 7 and 13 7 respectively these values include the free surface effect and are in reasonable agreement with the impedance contrast from the borehole logs at the granite site amplification of both p and s waves is less than four direct wave amplification at the wellhead is therefore at least three times that of the granite site the spectra of the direct and coda waves of the one earthquake recorded at both the wellhead and granite sites are compared with the corresponding 2 9 km recording coda wave amplification is in good agreement with the direct wave at the rock site but at the borehole the coda wave amplification factor overestimates the direct wave amplification by a factor of 3

simultaneous determination of site responses and source parameters of small earthquakes along the atotsugawa fault zone central japan velocity seismograms recorded at nine local stations from 102 small earthquakes on the atotsugawa fault zone central japan with seismic moment from 3 10 17 to 3 10 21 dyne cm are analyzed to obtain the s wave spectra a genetic algorithm is applied to determine the earthquake source parameters and site responses simultaneously the stability of both site responses and source parameters are experimentally tested as well as the effects of different q models the resulting source parameters show that the stress drops appear to vary systematically with the location of earthquakes events located on the mozumi fault or the junction of the mozumi and the atotsugawa faults have higher stress drops than those on the creeping section and southernmost part of the atotsugawa fault the relationship between seismic moment and corner frequency constructed by combining our results and those of iio 1986 for other regions in japan shows that a single scaling relation does not apply in a moment range of 10 10 to 10 25 dyne cm a steplike change in scaling relationship occurs between 5 10 18 and 5 10 20 dyne cm corresponding to corner frequencies between 15 and 25 hz this observation suggests that earthquakes are most likely a multihierarchical system divided by characteristic sizes according to aki9s 1980 model a characteristic source dimension 100 200 meters may represent a critical size of the barriers distributed in the fault zone at which the barrier effects are balanced by the dynamic effect of the source process

earthquake source parameters and fault kinematics in the eastern california shear zone based on waveform data from a profile of aftershocks following the north south trace of the 28 june 1992 landers rupture across the mojave desert we construct a new velocity model for the mojave region that features a thin slow crust using this model we obtain source parameters including depth and duration for each of the aftershocks in the profile and in addition any significant m 3 7 joshua tree landers aftershock between april 1992 and october 1994 for which coherent terrascope data were available in all we determine source parameters and stress drops for 45 significant m w 4 earthquakes associated with the joshua tree and landers sequences using a waveform grid search algorithm stress drops for these earthquakes appear to vary systematically with location with respect to previous seismic activity proximity to previous rupture i e with respect to the landers rupture and with tectonic province in general for areas north of the pinto mountain fault stress drops of aftershocks located off the faults involved with the landers rupture are higher than those located on the fault with the exception of aftershocks on the newly recognized kickapoo landers fault stress drops are moderate south of the pinto mountain fault where there is a history of seismic swarms but no single throughgoing fault in contrast to aftershocks in the eastern transverse ranges and related to the 1992 big bear california sequence landers events show no clear relationship between stress drop and depth instead higher stress drop aftershocks appear to correlate with activity on nascent faults or those that experienced relatively small slip during mainshock rupture

the 20 hz signals of finback whales balaenoptera physalus the 20 hz signals of finback whales balaenoptera physalus were analyzed from more than 25 years of recordings at a variety of geographic locations on near surface hydrophones close to whales and on deep hydrophone systems these signals were composed of 1 s pulses of sinusoidal waveform with downward sweeping frequency from approximately 23 to 18 hz at variable source levels up to 186 db re 1 pa at 1 m usually with slightly lower levels for the pulses at the beginning and end of sequences these 20 hz pulses were produced in signal bouts separated by more than 2 h lasting as long as 32 5 h bouts were composed of regularly repeated pulses at intervals of 7 26 s typically either at one nominal pulse rate or at two alternating doublet pulse intervals signal bouts were interrupted by rests of 1 20 min at roughly 15 min intervals and by irregular gaps lasting between 20 and 120 min the distribution of these signals throughout the year and their temporal sequence were analyzed from the cont

why is amazonitic k feldspar an earmark of nyf type granitic pegmatites clues from hybrid pegmatites in madagascar the presence of amazonitic k rich feldspar is considered an earmark of evolved granitic pegmatites ofnyf type elements of an explanation of the nyf pegmatite amazonite connection emerged in a study of the classic anjanabonoina hybrid granitic pegmatite in madagascar the nyf assemblages there and at the sakavalana and anjahamiary pegmatites contain magmatic u and th rich accessory phases and an amazonitic microcline perthite in miarolitic cavities the early miarolitic minerals are overgrown by a li and cs enriched assemblage depleted in hfse containing pale gray microcline perthite the amazonitic microcline perthite at anjanabonoina has a 18 o value above 15 o and that at sakavalana close to 13 o indicative of formation of the nyf pegmatite forming magma by the melting of crustal rocks locally the source rocks had become slightly alkaline and enriched in hfse during periods of metasomatism of the hot granulitic crust accompanying episodes of distension over the course of the protracted pan african orogeny the fertilized crust underwent local anatexis after the culmination of gondwana re assembly the proximity of pyrochlore and other u and th bearing accessory phases in the nyf assemblage provided the ionizing radiation required to interact with h 2 o trapped in the vacancy next to the pb ions in the structure the presence of an amazonitic k feldspar ultimately signals net additions of pb u th and the alkalis to the source prior to anatexis during a period of distension after a major orogenic disturbance plumbian k feldspar also occurs in granitic pegmatite bodies formed by anatexis in the vicinity of a galena bearing orebody e g at broken hill australia in this case the resulting granitic pegmatite is neither of nyf type nor enriched in rare elements however

earthquake source scaling relationships from 1 to 5 ml using seismograms recorded at 2 5 km depth the scaling relationships of earthquake sources less than about magnitude 3 have been the subject of considerable controversy over the last two decades studies of such events have shown a tendency for the constant stress drop self similarity of larger earthquakes to breakdown at small magnitudes and an apparent minimum source dimension of about 100 m has been observed other studies showed that this apparent breakdown in scaling could be an artifact of severe near surface attenuation limiting the spatial resolution of surface data in this study source parameters are determined for over 100 nearby tectonic earthquakes from recordings at a depth of 2 5 km in granite in the cajon pass scientific drill hole southern california comparison of the seismograms recorded at this depth with those at the wellhead clearly demonstrates the effect of the severe attenuation in the upper kilometers of the earth s crust source parameters are calculated by spectral modeling of three component p and s waves assuming four source models based on the brune 2 n 2 model in model l n 2 is fixed and q of p and s waves is determined to be 912 581 1433 and 1078 879 1323 respectively the numbers in parentheses are 1 standard deviation in model 2 qp qs 1000 is assumed and n is allowed to vary the 2 model is a good average for the data set but there is some real scatter supported by the data in model 3 qp qs 1000 is also assumed and 2 is constrained and in model 4 attenuation is ignored and n is allowed to vary source dimensions of less than 10m are observed for all four models 10 times smaller than the proposed minimum no breakdown in constant stress drop scaling is seen in the downhole data approximately ml 1 to 5 5 m0 109 1016 nm the ratio between radiated seismic energy estimated by integrating the velocity squared spectra with adequate signal bandwidth and seismic moment appears to decrease gradually with decreasing moment in the magnitude range 1 to 7 this is not incompatible with a constant stress drop but could result from errors in calculating energy the ratio of the s wave energy to that radiated by the p waves is about 14 after correction for attenuation this low value is consistent with the corner frequency shift of about 1 3 this corner frequency shift is observed for all four source models and therefore is interpreted as being source controlled

high frequency p wave attenuation determination using multiple window spectral analysis method yellowknife array northwest territories canada recordings of nuclear explosions detonated at french tuamotu south pacific and shagan river eastern kazakhstan ussr test sites are used to derive t values via the application of the spectral decay method an important factor that limits the reliability of this widely used method is the degree of accuracy with which one is able to determine the signal spectral shape for transient pulse like short period teleseismic phases the conventional single window spectral estimate methods may not be appropriate due to the trade off betgween the leakage resistance and variance a recently developed multiple window spectral analysis method is used in this study to effectively control spectral leakage a capability that is especially important when analyzing seismic data characterized by a rapid high frequency fall off rate such as the french tuamotu explosion data we compare the t estimates obtained using a conventional single window method with those obtained using the multiple window method and show that the latter are more reliable the f 0 5 to 4 5 hz found by the multiple window method for the tuamotu yellowknife path is 0 66 sec for the eastern kazakhstan yeliowknife path the multiple window t estimate is 0 42 sec in the 0 5 to 4 5 hz range a smaller value is obtained at higher frequencies 4 5 to 8 hz

scale dependence of apparent stress for earthquakes along the subducting pacific plate in northeastern honshu japan apparent stress which quantifies the ratio of high frequency spectral amplitude to the direct current level of source displacement spectra is known to reflect the source rupture process whether this parameter depends on the seismic moment has not yet been well established because of the difficulties in the reliable estimation of high frequency source spectra to overcome this problem we estimate s wave source spectra by using site amplification factors and attenuation factor graphic 1 which are systematically measured by the coda normalization method analyzing horizontal components of velocity seismograms recorded at 70 borehole seismic stations of hi net national research institute for earth science and disaster prevention in northeastern honshu japan we estimate site factors and graphic 2 in the 0 5 32 hz frequency band by using these factors we evaluate the source spectra of 225 small to moderate earthquakes that occurred in and around the subducting pacific plate site amplification factors we obtained strongly depend on frequency and the frequency dependence clearly changes with the lithology and geologic age of rock obtained graphic 3 values decrease with frequency in proportion to the reciprocal of frequency the apparent stresses estimated from s wave spectra clearly increase from 104 to 107 pa with the seismic moment increasing which cannot be attributed to the limited frequency band and other artificial causes the power of scale dependence is estimated as 0 39 0 44 for the seismic moment range from 1011 to 1017 n m some of the scale dependence of apparent stress is attributed to the scale dependence of brune s stress drop 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif 3 embed inline graphic 3 gif

petrology and isotope geochemistry of the mesoproterozoic anorthosite and related rocks of the kunene intrusive complex nw namibia abstract the intrusion of the large c 18 000 km2 anorthosite body of the kunene intrusive complex angola namibia which is associated with minor marginal granite bodies and syenite syenodiorite dykes marked the beginning of mesoproterozoic igneous activity in nw namibia anorthosites display an igneous mineral assemblage of dominating plagioclase together with minor olivine orthopyroxene or clinopyroxene fe ti oxides whereas biotite and pargasite are late magmatic phases apatite is a common accessory phase in regionally associated felsic rocks k feldspar plagioclase clinopyroxene and or hastingsite crystallized first followed by interstitial quartz hastingsite fe ti oxides and titanite the general geochemical characteristics for the anorthositic rocks of the kunene intrusive complex i e high al2o3 cao sr and eu intermediate to high mg numbers of 0 37 0 74 positive nd t values of 3 0 to 1 0 and initial sr ratios of 0 7028 0 7041 are in excellent agreement with their derivation from fractionated basaltic liquids the 18o values obtained for plagioclase 5 88 0 19 18o support their development from mantle derived magmas relic crustal xenoliths of calc silicate rocks and sr and nd isotope data however suggest that the anorthosite magma underwent minor crustal contamination which was most prominent during the early intrusion stage a u pb zircon age of 1376 2 ma was obtained for a felsic rock associated with the 1385 25 ma anorthosites which suggests that the two suites were emplaced during the same igneous event the geochemical and isotope signatures of the granites syenites and syenodiorites provide convincing evidence against consanguinity of the anorthositic and the felsic rock suites i e 1 a compositional gap exists between the major and trace element contents of the two suites 2 trace element and sr and nd isotopic data of the felsic rocks point to a crustal source nd 2 0 to 0 4 initial sr ratio 0 7024 0 7063 3 the ree patterns of the felsic rocks do not exhibit ubiquitous negative eu anomalies which would be expected from fractionation products of melts that previously formed extensive plagioclase cumulates and 4 18o values of magmatic feldspar from the felsic rock suite fall in a restricted range 7 20 7 92 that is about 1 6 higher than the average igneous plagioclase 18o of the anorthosites and suggests a formation of the felsic melts by anatexis of the lower crust

earthquake stress drops and inferred fault strength on the hayward fault east san francisco bay california we study variations in earthquake stress drop with respect to depth faulting regime creeping versus locked fault behavior and wall rock geology we use the p wave displacement spectra from borehole seismic recordings of m 1 0 4 2 earthquakes in the east san francisco bay to estimate stress drop using a stack and invert empirical green s function method the median stress drop is 8 7 mpa and most stress drops are in the range between 0 4 and 130 mpa an apparent correlation between stress drop and magnitude is entirely an artifact of the limited frequency band of 4 55 hz there is a trend of increasing stress drop with depth with a median stress drop of 5 mpa for 1 7 km depth 10 mpa for 7 13 km depth and 50 mpa deeper than 13 km we use s p amplitude ratios measured from the borehole records to better constrain the first motion focal mechanisms high stress drops are observed for a deep cluster of thrust faulting earthquakes the correlation of stress drops with depth and faulting regime implies that stress drop is related to the applied shear stress we compare the spatial distribution of stress drops on the hayward fault to a model of creeping versus locked behavior of the fault and find that high stress drops are concentrated around the major locked patch near oakland this also suggests a connection between stress drop and applied shear stress as the locked patch may experience higher applied shear stress as a result of the difference in cumulative slip or the presence of higher strength material the stress drops do not directly correlate with the strength of the proposed wall rock geology at depth suggesting that the relationship between fault strength and the strength of the wall rock is complex

pb u and th diffusion in natural zircon zircon zrsio4 is one of the most widely used minerals for determining the age origin and thermal history of rocks by u th pb geochronology but the parameters describing the solid state volume diffusion rates of these elements in natural zircon which are themselves important for establishing the limits on the applicability of zircon for geochronological studies have remained poorly quantified1 this is because of the measurement difficulties associated with the low p p m concentrations and low diffusion rates of these elements in natural zircon and the chemical and physical heterogeneity present in most crystals here we present direct measurements of the uranium thorium and lead loss from a thermally treated gem quality natural zircon and show that lead diffuses much faster than uranium or thorium we find that the u th pb isotopic system in natural zircon will typically have a closure temperature greater than 900 c which explains why zircon is apparently such a robust geochrometer and is capable of remaining isotopically closed through extended periods of high grade metamorphism and partial melting of the host rock

hard rock spectral models for intermediate depth vrancea romania earthquakes the frequency dependent amplification for rock sites as well as apparent source spectra were studied using an earthquake ground motion database collected in romania almost all events occurred in the vrancea focal zone southeast carpathians which is characterized by a high rate of occurrence of large earthquakes in a narrow focal volume the seismic activity ranges within an almost vertical stripe in depths between 60 and 170 km the database used includes several hundred records from more than 100 small magnitude m w 3 5 5 3 earthquakes that occurred in 1996 2004 and six acceleration records obtained during four large m w 7 2 6 9 6 3 and 6 0 earthquakes the characteristics of amplification were evaluated using the well known technique of horizontal to vertical h v fourier spectral ratio of the s wave phase lermo and chavez garcia 1993 the apparent source spectra were obtained from horizontal components using site h v propagation path geometric spreading and anelastic attenuation and near surface attenuation kappa factor corrections seismic radiation within the frequency range from 0 2 0 3 to 15 20 hz during the earthquakes of various magnitudes in the vrancea zone may be described by an omega square single corner frequency spectral model 2 brune spectrum the stress parameter which controls high frequency spectral amplitudes increases with magnitude from 20 30 bars for m w 3 5 up to 200 250 bars for m w 4 8 5 3 and up to 1000 bars for the case of large m w 6 0 6 5 events empirical amplification h v for rock sites showing stability for particular locations reveal high variability from station to station which together with variations of values of kappa reflects influence of local geologic and geomorphologic factors

can acoustic multipath explain finback b physalus 20 hz doublets in shallow water a broadband acoustic propagation code is combined with an empirically derived geoacoustic seafloor model for the purpose of interpreting finback doublet sequences recorded in the northern gulf of california by thompson et al in 1987 thompson et al j acoust soc am 92 3051 3057 1992 the result is that for ranges less than 30 km it is plausible to explain the appearance of the finback doublet in this environment in terms of multipath propagation through the water column and the seafloor for a channel depth as shallow as 50 m the detection range of the subbottom arrival may exceed that of the water borne arrival this result may have important implications for the accuracy of hyperbolic localization algorithms which assume a sound speed consistent with a water borne propagation path when doublet propagation is supported the interpulse delay is demonstrated to be strongly range dependent with prior knowledge of the geoacoustic environment the interpulse delay may provide a practical tool for the real time passive ranging of finbacks using only a single hydrophone or sensor array scientists might consider the impact the multipath induced doublet has on long distance communication between whales based on temporal cues encoded in patterned 20 hz pulse sequences

stress drop variations and source scaling relations of moderate earthquakes of the indian tectonic plate we investigate the source characteristics of 53 earthquakes in and around the indian subcontinent through a grid search technique applied to the p and s wave displacement spectra of regional waveforms registered at 42 broadband seismic stations in addition we estimate the p and s wave attenuation factors representative of the various tectonic regions that constitute the indian shield we discuss the sensitivity of the displacement spectrum to various parameters and demonstrate that for a brune type source model the seismic moment is the best estimated parameter compared to others such as the corner frequency our estimates of moment magnitudes are within the range of 1014 1020 n m with the crack radii being less than 12 km the nonuniform distribution of the static stress drop along the himalaya burmese arc and the western indian regions indicates that the central himalayas are prone to frequent failures owing to the lesser stress drop in contrast with the northwestern himalaya and burmese arc regions our results suggest that median stress drops are independent of the earthquake mechanism online material list of events and associated estimated parameters

estimation of seismic site response in the tangshan area china using deep underground records site amplification in the tangshan area china was analyzed using records of small events m l 2 9 4 4 observed by a strong motion array with a deep 822 m underground station deployed between 1982 and 1984 following the 1976 tangshan earthquake the effect of destructive interference at the underground site due to surface reflections was confirmed to be negligible in this case the source propagation path and site effects were separated simultaneously by linear inversion using the underground reference site the s wave quality factor was found to be approximated by the relation 29 f 0 9 in the frequency range 1 10 hz the conventional surface rock reference site was found to have a characteristic frequency dependent site effect which increased markedly from the theoretical amplification factor of 2 over the frequency range of interest a reference independent technique assuming an squared source model was also introduced and produced results that were in good agreement with the results obtained using the underground reference the reference independent technique revealed the underground station to have a nearly flat response consistent with the theoretical response indicating that an underground or borehole bedrock site is a better reference than a surface rock for seismic hazard analysis the reference independent technique produced accurate absolute site amplification factors for the area examined in this study demonstrating the usefulness of the method for site effect analysis

passive acoustic detection and localization of whales effects of shipping noise in saguenay st lawrence marine park the performance of large aperture hydrophone arrays to detect and localize blue and fin whales 15 85hz signature vocalizations under ocean noise conditions was assessed through simulations from a normal mode propagation model combined to noise statistics from 15960h of recordings in saguenay st lawrence marine park the probability density functions of 2482 summer noise level estimates in the call bands were used to attach a probability of detection masking to the simulated call levels as a function of whale depth and range for typical environmental conditions results indicate that call detection was modulated by the calling depth relative to the sound channel axis and by modal constructive and destructive interferences with range masking of loud infrasounds could reach 40 at 30km for a receiver at the optimal depth the 30db weaker blue whale d call were subject to severe masking mapping the percentages of detection and localization allowed assessing the performance of a six hydrophone array under

determination of earthquake energy release and ml using terrascope we estimated the energy radiated by earthquakes in southern california using on scale very broadband recordings from terrascope the method we used involves time integration of the squared ground motion velocity and empirical determination of the distance attenuation function and the station corrections the time integral is typically taken over a duration of 2 min after the p wave arrival the attenuation curve for the energy integral we obtained is given by q r cr n exp kr r 2 2 h ref 2 with c 0 49710 n 1 0322 k 0 0035 km 1 and h ref 8 km where is the epicentral distance a similar method was used to determine m l using terrascope data the station corrections for m l are determined such that the m l values determined from terrascope agree with those from the traditional optical wood anderson seismographs for 1 5 6 5 m l saturates the ratio e s m 0 m 0 seismic moment a measure of the average stress drop for six earthquakes the 1989 montebello earthquake m l 4 6 the 1989 pasadena earthquake m l 4 9 the 1990 upland earthquake m l 5 2 the 1991 sierra madre earthquake m l 5 8 the 1992 joshua tree earthquake m l 6 1 and the 1992 landers earthquake m w 7 3 are about 10 times larger than those of the others that include the aftershocks of the 1987 whittier narrows earthquake the sierra madre earthquake the joshua tree earthquake and the two earthquakes on the san jacinto fault the difference in the stress drop between the mainshock and their large aftershocks may be similar to that between earthquakes on a fault with long and short repeat times the aftershocks which occurred on the fault plane where the mainshock slippage occurred had a very short time to heal hence a low stress drop the repeat time of the major earthquakes on the frontal fault systems in the transverse ranges in southern california is believed to be very long a few thousand years hence the events in the transverse ranges may have higher stress drops than those of the events occurring on faults with shorter repeat times such as the san andreas fault and the san jacinto fault the observation that very high stress drop events occur in the transverse ranges and the los angeles basin has important implications for the regional seismic potential the occurrence of these high stress drop events near the bottom of the seismogenic zone strongly suggests that these fault systems are capable of supporting high stress that will eventually be released in major seismic events characterization of earthquakes in terms of the e s m 0 ratio using broadband data will help delineate the spatial distribution of seismogenic stresses in the los angeles basin and the transverse ranges

simple methods of estimating source levels and locations of marine animal sounds this paper describes three relatively simple methods of estimating source levels of marine animal sounds by estimating the source distance acoustically using one or two hydrophones the methods are logistically simpler than using arrays of hydrophones of known positions but are accurate over a smaller range of distances one method makes use of the differences in the arrival times and levels of the signals received at two hydrophones from the same sound emission no knowledge of the positions of the hydrophones is required however if these are known the position of the source can be determined with left right ambiguity the second method uses the difference in received levels only but requires the hydrophone spacing to be known adequate accuracy requires the source to be significantly closer to one hydrophone than to the other third if the direct and surface reflected arrivals can be separated the source level can be determined with a single hydrophone the methods require accurately calibrated hydrophones

source parameters of the 1980 mammoth lakes california earthquake sequence from the more than 1500 mammoth lakes earthquakes recorded on three component digital seismographs spudich et al 1981 150 were used in an analysis of the locations mechanism and source parameters a composite fault plane solution of nine earthquakes 3 9 m 5 1 defines a right lateral strike slip mechanism on a steeply dipping nearly east west plane striking s75 e or left lateral strike slip on a nearly north south plane striking n10 e vertical cross sections of well located aftershocks indicate possibly three east west planes that coincide with the locations of the four largest earthquakes with ml 6 0 using the spectral analysis of s waves brune 1970 source parameters for 67 earthquakes were determined forty eight had magnitudes greater than or equal to 3 0 seismic moments ranged from 9 20 1018 dyn cm to 2 33 1024 dyn cm earthquakes with seismic moment greater than about 1 0 1021 dyn cm had nearly constant stress drops 50 bars earthquakes with seismic moment less than about 1 0 1021 dyn cm had stress drops that apparently decrease as seismic moment decreases

seismic attenuation above 10 hz in southern california from coda waves recorded in the cajon pass borehole we estimate the attenuation around cajon pass southern california for frequencies above 10 hz and we find total q to exhibit only weak frequency dependence ranging from 800 at 10 hz to 1500 at 100 hz the intrinsic attenuation is approximately twice the level of the scattering attenuation measurements are made using earthquake seismograms recorded at 0 3 km depth using the multiple lapse time window method the results are not dependent on receiver depth and are consistent with previous estimates of q made from direct waves recorded at 2 5 km depth our q values are therefore thought to be representative of the seismogenic crust and the technique used is uncontaminated by the highly attenuating near surface at least above 10 hz we also calculate q from surface data between 1 and 10 hz and find a clear change in the frequency dependence of both intrinsic and scattering attenuation at 10 hz q exhibits strong frequency dependence below 10 hz 1 8 consistent with previous studies in active tectonic regions and only weak frequency dependence at higher frequencies 0 34 this change in behavior renders it unwise to extrapolate q measurements outside the frequency range from which they were derived for example in earthquake source studies possible factors responsible for the apparent change in frequency dependence of q are considered further work is required however to resolve the causes of this change

observational constraints on earthquake source scaling understanding the limits in resolution abstract i examine the resolution of the type of stress drop estimates that have been used to place observational constraints on the scaling of earthquake source processes i first show that apparent stress and brune stress drop are equivalent to within a constant given any source spectral decay between 1 5 and 3 i e any plausible value and so consistent scaling is expected for the two estimates i then discuss the resolution and scaling of brune stress drop estimates in the context of empirical green s function results from recent earthquake sequences including the 1992 joshua tree california mainshock and its aftershocks i show that no definitive scaling of stress drop with moment is revealed over the moment range 1019 1025 within this sequence however there is a tendency for moderate sized m 4 5 events to be characterized by high stress drops however well resolved results for recent m 6 events are inconsistent with any extrapolated stress increase with moment for the aftershocks focusing on corner frequency estimates for smaller m

source scaling and site effects at vesuvius volcano the site corrected source scaling pattern is estimated for local earthquakes 0 9 m d 3 6 at mt vesuvius the dataset comprises 35 low to moderate local earthquakes recorded by 14 three component seismic stations during 1993 1996 and 1999 site transfer functions in the frequency range 1 hz 25 hz are estimated from the spectra of s waves and coda waves and from the horizontal to vertical h v spectral ratios we applied the direct spectral ratios method to s waves considering as a reference the average spectrum and the inversion method to s waves and coda waves the site amplification on the coda waves was also compared with that evaluated using the wavelet transform the standard deviation associated with the experimental results is computed for all of the used methods results indicate a general agreement among the methods and the site transfer functions show interesting features the highest amplifications are found for frequencies lower than 12 hz for sites located at lower altitude the methods based on coda waves show highest amplification with respect to the methods based on s waves for most of the sites located in the summit part of the volcano this can be a phenomenon of coda localization which consists in the trapping inside the upper part of the volcano of scattered waves the h v spectral ratios do not show total agreement with the other methods mostly for the sites located in the summit part of the volcano the discrepancies among the results obtained in this work are also due to the different normalization applied in the methods of analysis generalized inversion method allowed us to estimate the source scaling of the site corrected source seismic spectrum for the investigated area the source scaling obtained in terms of seismic moment and source radii shows that the seismicity of mt vesuvius is characterized by stress drop as low as a few bars 10 bars except for the event of graphic 1 graphic 2 the scaling pattern shows an apparent linear relationship between source size and seismic moment for m d 3 3 but the statistical test shows that the linear trend has low reliability 1 embed inline graphic 1 gif 2 embed inline graphic 2 gif

attenuation of short period p waves at mount st helens an increase of seismicity occurred at mount st helens between may and july 1998 with more than 900 events md 2 2 recorded by the pacific north west seismograph network this article describes an attempt to estimate the temporal and spatial variation in seismic attenuation using 200 microearthquakes that occurred before january 1995 april 1998 during and after august december 1998 the period of higher seismicity and recorded on three different one component seismic stations epicentral distances of the studied events ranged between 0 5 and 15 km we performed the analysis distinguishing the deep depth 5 5 km from shallow depth 5 5 km events we used the frequency decay method to estimate the quality factor q and station site correction s for p waves in the frequency bands 2 7 and 18 30 hz the results show that the attenuation varies from site to site systematically and decreases with depth lower qp values are obtained for focal depths less than 5 5 km moreover the spatial variations of qp show minimum values 30 in the crater area that are interpreted as due to a low density mass distribution under the crater we find that qp was 30 higher before the period of high seismicity than after this change may be attributed to an increase of pressure in the magma chamber producing new cracks and or reopening of pre existing cracks which are the most viable mechanisms for increasing attenuation

internal structures of zircons from archaean granites from the darling range batholith implications for zircon stability and the interpretation of zircon u pb ages internal structures in zircons from granitoids from the late archaean darling range batholith show secondary features revealed by hf etching which record reconstitution of the zircons and modification of the distribution of trace elements during post crystallisation cooling of the granitoid zircons from the granites commonly contain unzoned to weakly zoned cores surrounded by rims showing oscillatory zoning which has been modified by recrystallisation the most striking feature is the development of high trace element concentration areas found in zircons from a number of granites these structures range from enhanced trace element concentrations in primary zones to a single accumulation of most trace elements in one band about half way between the outer edge and the centre of the zircon in any zircon the extent of the concentration of trace elements towards the formation of a single trace element band appears to be inversely related to the fading and broadening of primary oscillatory zones in the outer rim this suggests that the trace element bands formed by migration of trace elements from the outer primary zones to new concentration sites on an inner set of primary zones this explanation is supported by the formation of multiple curved trace element bands that transgress primary zoning and the determination of younger shrimp ages on depleted zircon outer rims compared to remnant primary oscillatory zoned areas of the zircon and unzoned centres also observed in some granite zircons is a finely convoluted zoning which overprints oscillatory zoning in parts of a zoned zircon and in rare cases occurs throughout the zircon this structure is explained in terms of secondary migration and reconcentration of trace elements in curved bands all structures can be transgressed by generally rounded lobes and patches of low u weakly nebulously zoned zircon this is interpreted as a late stage interaction between the zircon and fluids formed during cooling and crystallisation of the granitoid resulting in recrystallisation of affected parts of the zircon with accompanying loss of trace elements from the zircon

seismic source spectrum of microearthquakes the seismic source spectra of microearthquakes having seismic moments between 1014 and 1018 dyne cm were investigated by using local recordings from an excellent hard rock site the p wave velocity near the site was estimated as about 6 km sec even immediately below the ground surface the effect of anelastic attenuation was thought to be very small since predominant frequencies of greater than 100 hz were detected in seismograms recorded at focal distances greater 10 km many seismograms with s p times of less than 0 6 sec were observed the first cycle of the p wave velocity seismogram was used in this study the waveforms after the first cycle are likely formed near the site since their periods are exactly the same for earthquakes that have different source processes in the high frequency portion of the estimated displacement source spectra the slopes of the fall off have values much greater than 2 the source process of microearthquakes is assumed to be very slow and smooth

description and seasonal detection of two potential whale calls recorded in the indian ocean unidentified acoustic signals are recorded by hydrophones placed in the world s oceans some of these sounds are suspected to originate from marine mammals in this study two acoustic signals recorded by two arrays at diego garcia in the northern indian ocean are described data were available between january 2002 and december 2003 signals were detected manually using long term spectral average plots time and frequency measurements were taken from a sample of both signals the first unidentified signal diego garcia downsweep dgd consisted of two main components the mean frequency range of the entire signal was 19 3 45 0 hz with a mean duration of 36 5 s n 22 detections of dgd at the northern array peaked in the austral summer though detections at the southern array peaked during winter and spring the second unidentified signal diego garcia croak dgc consisted of one component with a mean frequency range of 16 9 49 6 hz the mean duration of the signal was 13 1 s n 10 detections of dgc did not follow a clear seasonal pattern these signals followed characteristics of biological sources suggesting that they could be whale calls fin whale calls and possible blue whales d calls were also identified in the data

matched field processing geoacoustic inversion and source signature recovery of blue whale vocalizations matched field processing mfp and global inversion techniques have been applied to vocalizations from four whales recorded on a 48 element tilted vertical array off the channel islands in 1996 global inversions from selected whale calls using as few as eight elements extracted information about the surrounding ocean bottom composition array shape and the animal s position these inversion results were then used to conduct straightforward mfp on other calls the sediment sound speed inversion estimates are consistent with those derived from sediment samples collected in the area in general most animals swam from the east to west but one animal remained within 500 m of its original position over 45 min all whales vocalized between 10 and 40 m depth three acoustic sequences are discussed in detail the first illustrating a match between an acoustic track and visual sighting the second tracking two whales to ranges out to 8 km and the final sequence demonstrating high resolution dive profiles from

termination of a 6 year ridge spreading event observed using a seafloor seismic network on the endeavour segment juan de fuca ridge 1 we present automatically determined epicenters and magnitudes for 36 523 earthquakes recorded along the endeavour segment between august 2003 and october 2006 using a local ocean bottom seismometer obs network the catalog is dominated by two swarm sequences in january and february 2005 in the vicinity of the endeavour overlapping spreading center which included earthquakes in west valley the northern portion of the endeavour segment southwest endeavour valley and the endeavour vent fields these swarms are attributed to volcanism including a dike intrusion on the northern endeavour in february 2005 and smaller diking events on the propagating tip of the west valley segment in both swarms the dike on the northern endeavour propagated to the south which is inconsistent with magma sourced from the axial magma chamber beneath the elevated central portion of the segment following the swarms seismic activity on the endeavour segment decreased on average to 15 of pre swarm values and almost ceased at the segment ends we infer that a 6 year non eruptive event that started with a swarm in 1999 and finished with the 2005 swarms ruptured the entire segment and relieved plate spreading stresses the inferred coupling between the 1999 and 2005 events the observation of extensive precursory activity prior to the 2005 swarms and the interaction between seismically active regions during the swarms is consistent with static triggering with delays influenced by viscoelastic relaxation hydraulic diffusion and magma withdrawal and replenishment

minimum size of earthquakes and minimum value of dynamic rupture velocity abstract the very small aftershocks of the 1984 western nagano prefecture japan earthquake mjma 6 8 were studied in order to investigate the faulting processes of small earthquakes earthquakes with m the fault length l of the smallest event is estimated to be 1 5 m by using relationships between seismic moment and fault length which are derived from aftershock areas the rupture velocity of the smallest event is calculated to be 50 250 m s from the fault length and the pulse width of the source time function these values are much smaller than those of large earthquakes 2 3 km s it was deduced by iio 1986a that smaller earthquakes with m0

frequency dependent attenuation of high frequency p and s waves in the upper crust in western nagano japan borehole seismograms from local earthquakes in the aftershock region of the 1984 western nagano prefecture japan earthquake were analyzed to measure the frequency dependent characteristics of p and s wave attenuation in the upper crust the records from a three component velocity seismometer at the depth of 145m exhibit high s n ratio in a wide frequency range up to 100 hz extended coda normalization methods were applied to bandpass filtered seismograms of frequencies from 25 to 102 hz for the attenuation of high frequency p and s waves our measurements show q p 1 0 052 0 66 and q s 1 0 0034 0 12 respectively the frequency dependence of the quality factor of s waves is very weak as compared with that of p waves the ratio of q p 1 q s 1 is larger than unity in the entire analyzed frequency range

origin of the high variability of water mineral content in the bedrock aquifers of southern madagascar this study assesses the causes of the high spatial variability of the mineral content of groundwater in crystalline bedrock of southern madagascar although many kilometres from the coast and at a mean altitude of 400 m a s l wells drilled in this area produce water with electrical conductivities in the range of 300 30 000 mu s cm 1 with a high spatial variability chemical and isotopic data are used to identify the processes involved in the groundwater mineralization it is shown that the chemical composition of the groundwater in this region has its origin in i normal silicate and carbonate weathering reactions and ii input of marine salts probably via rainfall recharge modified by evapo concentrative processes probably including precipitation and re dissolution of secondary evaporites in the unsaturated zone to obtain a better understanding of the spatial salinity distribution well parameters such as yields weathered zone thickness weathered materials and morphological positions upper slope mid slope lower slope or valley bottom are scrutinized a correlation was found between high salinity and low flow shallow groundwater environments flat hill tops valley bottoms weakly developed and clayey weathered zones and between low salinity and high flow environments granular well developed weathered zones and situation on valley slopes

trace element zoning and incipient metamictization in a lunar zircon application of three microprobe techniques we have determined major si zr hf minor al y fe p and trace element ca sc ti ba ree th u concentrations and raman spectra of a zoned 200 microns zircon grain in lunar sample 14161 7069 a quartz monzodiorite breccia collected at the apollo 14 site analyses were obtained on a thin section in situ with an ion microprobe an electron microprobe and a laser raman microprobe the zircon grain is optically zoned in birefringence a reflection of variable incomplete metamictization resulting from zo nation in u and th concentrations variations in the concentrations of u and th correlate strongly with those of other high field strength trace elements and with changes in raman spectral parameters concentrations of u and th range from 21 to 55 ppm and 6 to 31 ppm respectively and correlate with lower raman peak intensities wider raman peaks and shifted si o peak positions concentrations of heavy rare earth elements range over a factor of three to four and correlate with intensities of fluorescence peaks correlated variations in trace element concentrations reflect the original magmatic differentiation of the parental melt approx 4 b y ago degradation of the zircon structure as reflected by the observed raman spectral parameters has occurred in this sample over a range of alpha decay event dose from approx 5 2 x 10 exp 14 to 1 4 x 10 exp 15 decay events per milligram of zircon as calculated from the u and th concentrations this dose is well below the approx 10 exp 16 events per milligram cumulative dose that causes complete metamictization and indicates that laser raman microprobe spectroscopy is an analytical technique that is very sensitive to the radiation induced damage in zircon

the link between an anorthosite complex and underlying olivine ti magnetite rich layered intrusion in damiao china insights into magma chamber processes in the formation of proterozoic massif type anorthosites mafic ultramafic intrusions comagmatic with proterozoic massif type anorthosites can provide insights into the parental magma from which large volumes of hyper feldspathic rocks are produced recent deep drilling has unveiled a large olivine ti magnetite rich layered intrusion named dawusunangou beneath the damiao massif type anorthosite complex in the north china craton the layered intrusion is composed of alternating olivine ti magnetite rich dark layers and plagioclase rich light layers ca 35 80 plagioclase with the latter also containing pod or lens shaped pyroxene ti magnetite rich aggregates this layered intrusion shows low mg and ree patterns similar to the overlying damiao anorthosite complex baddeleyite pb pb geochronology yielded indistinguishable crystallization ages of ca 1735 ma for both the dawusunangou layered intrusion and the damiao anorthosite complex suggesting coeval emplacement using the average bulk compositions of the two intrusions mass balance calculations assuming 30 40 dawusunangou and 70 60 damiao would give a composition similar to high al basaltic magma collectively these features indicate that the dawusunangou layered intrusion represents the mafic residues after the segregation of the damiao anorthosites from high al basaltic parental magma a short lived magma chamber is thought to have supplied the two intrusions in situ crystallization with variable nucleation rates for plagioclase combined with the mafic minerals crystallizing in equilibrium proportions resulted in the formation of repeated dark and light layers of the dawusunangou layered intrusion the two intrusions are interpreted to have formed by multiple magma injections instead of continuous differentiation of one melt the parental magma was derived from a depleted mantle source with significant crustal contribution during magma evolution the large nd hf isotopic variations suggest contamination by paleoarchean to neoarchean crust

tracking fin whales in the northeast pacific ocean with a seafloor seismic network ocean bottom seismometer obs networks represent a tool of opportunity to study fin and blue whales a small obs network on the juan de fuca ridge in the northeast pacific ocean in 2 3 km of water recorded an extensive data set of 20 hz fin whale calls an automated method has been developed to identify arrival times based on instantaneous frequency and amplitude and to locate calls using a grid search even in the presence of a few bad arrival times when only one whale is calling near the network tracks can generally be obtained up to distances of 15 km from the network when the calls from multiple whales overlap user supervision is required to identify tracks the absolute and relative amplitudes of arrivals and their three component particle motions provide additional constraints on call location but are not useful for extending the distance to which calls can be located the double difference method inverts for changes in relative call locations using differences in residuals for pairs of nearby calls recorded on a common station the method significantly reduces the unsystematic component of the location error especially when inconsistencies in arrival time observations are minimized by cross correlation

comprehensive analysis of earthquake source spectra in southern california we compute and analyze p wave spectra from earthquakes in southern california between 1989 and 2001 using a method that isolates source receiver and path dependent terms we correct observed source spectra for attenuation using both fixed and spatially varying empirical green s function methods estimated brune type stress drops for over 60 000 m l 1 5 to 3 1 earthquakes range from 0 2 to 20 mpa with no dependence on moment or local b value median computed stress drop increases with depth in the upper crust from about 0 6 mpa at the surface to about 2 2 mpa at 8 km where it levels off and remains nearly constant in the midcrust down to about 20 km however the results at shallow depths could also be explained as reduced rupture velocities near the surface rather than a change in stress drop spatially coherent variations in median stress drop are observed with generally low values for the imperial valley and northridge aftershocks and higher values for the eastern transverse ranges and the north end of the san jacinto fault we find no correlation between observed stress drop and distance from the san andreas and other major faults significant along strike variations in stress drop exist for aftershocks of the 1992 landers earthquake which may correlate with differences in main shock slip

petrology and isotopic composition of a grenvillian basement fragment in the northern appalachian orogen blair river inlier nova scotia canada mesoproterozoic metaplutonic rocks in northern cape breton island introduction nova scotia occur in a tectonic inlier within the appalachian in eastern north america mesoproterozoic laurentian orogen although they have been multiply metamorphosed and basement rocks and their neoproterozoic to mid paleovariably deformed the petrology and geochemistry of these rocks zoic volcanic and sedimentary cover preserve a record provide insight into the tectonomagmatic evolution of easternmost of the proterozoic to mid paleozoic geologic history of laurentia anorthosite syenite and granitoid plutons eastern laurentia the record includes mesoproterozoic 1100 980 ma intruded the sailor brook and polletts cove river orogeny on the ancient north american craton breakgneisses new nd isotopic data are presented from a biotite rich up of a neoproterozoic supercontinent development of part of the sailor brook gneiss ndi 0 7 two anorthosite a passive continental margin and mid paleozoic orogeny samples ndi 2 1 and 2 8 and a charnockite unit exposures of mesoproterozoic laurentian basement in ndi 0 4 new u pb zircon data from the anorthosite yield easternmost canada and the usa occur in a dispb pb ages between 975 and 1095 ma disrupted u pb continuous band of inliers in the appalachian orogen systematics preclude a unique age interpretation but the 1095 ma from newfoundland to alabama fig 1 they consist single grain date is a minimum age for the anorthosite field relations mostly of rocks formed or deformed during major and trace element geochemistry and isotopic characteristics 1190 980 ma grenvillian tectonic and magmatic indicate that the anorthosite and charnockite were probably coexisting events and are distinct from neoproterozoic and melts but not differentiates of a single parent magma the lithological paleozoic units of accreted appalachian terranes in that and chemical characteristics of the lowland brook syenite are they include granulite facies metamorphic rocks and similar to those of a contemporaneous belt of ultrapotassic plutons in many cases anorthosite charnockite mangerite suites in the southern grenville province and both have the chemical bartholomew 1984 and papers therein pettingill et al characteristics of certain modern continental margin arc magmas 1984 rankin et al 1989 1993 owen erdmer 1990 these data indicate that the mesoproterozoic units in the blair hughes et al 1997 river inlier were juvenile crustal additions to eastern laurentia the sinuous trend of the band of basement inliers during grenville related orogenic events broadly reflects promontories and re entrants that formed

spectral analysis of k net and kik net data in japan part ii on attenuation characteristics source spectra and site response of borehole and surface stations abstract in this study we apply a nonparametric spectral inversion scheme to a data set of accelerograms recorded by the k net and kik net networks in japan in order to derive attenuation characteristics source spectra and site response for this purpose we use a total of more than 67 000 s wave records from 2178 earthquakes m jma 2 7 8 obtained at 1555 stations at the earth s surface and more than 29 000 records from 1826 events recorded at 637 borehole stations at depths of 100 to 3000 m attenuation characteristics are investigated in five separate regions showing that crustal q depicts lower values in central compared to southern japan and a significant frequency dependence is observed in every region the source spectra follow the 2 model with higher stress drops for subcrustal earthquakes as compared with crustal ones while strong amplification effects dominate the site contributions for the surface sensors those for the borehole sensors are characterized by smaller variability nevertheless consistent with observations from deconvolution of borehole surface recording pairs downgoing wave effects are visible in the site contributions for many borehole stations finally the site amplification functions obtained at the surface are compared with surface to borehole s b and horizontal to vertical h v spectral ratios showing that the s b ratios generally provide better estimates of the horizontal amplification than the h v ratios due to amplification of the vertical component of ground motion

slow cooling of deep crustal granulites and pb loss in zircon abstract we attempted to obtain the magmatic crystallization age of a metamorphosed granulite facies t 800 90 c p 8 1 kbar massif type anorthosite from the ankafotia body of southwest madagascar the sample studied is a coarse grained leuconorite with good preservation of igneous texture and mineralogy although plagioclase which contains abundant rutile and zircon inclusions has been slightly recrystallized thirty three isotope dilution u pb analyses of zircons representing single grain fragments 29 analyses and multi grain fractions 4 analyses yield a spectrum of concordant ages from 631 to 549 ma a time span of more than 80 myr back scattered electron and cathodoluminescence images show that most grains are either homogeneous structureless fragments 35 or are permeated to a variable degree by anastamosing cracks occupied by relatively u and or th enriched zircon 45 a smaller percentage of grains show relict magmatic zoning 20 thin u and or th rich overgrowths occur on about 25 of grains raman spot analyses demonstrate that all fragments are highly crystalline and non metamict there are marked correlations between zircon grain size and internal features such that the oldest grains are larger and show relict magmatic zoning the youngest grains are small fragments containing high u crack networks ion microprobe spot analyses show that each zircon grain preserves a distinct trace element signature rare earth element patterns show heavy ree enrichment with negative eu anomalies and positive ce anomalies we suggest that the ca 80 myr spread in concordant u pb ages in this sample is indicative of high temperature pb loss during one or more protracted periods of granulite facies metamorphism with only minor episodic or continuous metamorphic zircon growth volume diffusion and or fracture assisted diffusion seems to be the dominant mechanism of pb loss cooling curves calculated using recently measured pb diffusion parameters conform to the age size relationship and imply very slow cooling rates 1 2 c myr or less as might be expected for a terrane in which granulite conditions were maintained for an extended period of time our results therefore suggest a note of caution for interpretation of concordant zircon ages in meta igneous rocks affected by high grade metamorphism of long duration

fractal geometry in the san andreas fault system it has been noted that the spatial distribution of earthquakes and the mode of strain release in the san andreas fault system is related to the complexity of fault geometry because of their rough appearance over many length scales faults can be regarded as fractal surfaces direct estimates of fractal dimension d of portions of the san andreas fault system between the northern gabilan range and the salton sea including the postulated extent of the great 1857 fort tejon earthquake are obtained from measured fault lengths analogous to the lengths of coastlines as discussed by mandelbrot regions characterized by complicated fault geometry are associated with larger values of d based on fault traces mapped at a scale of 1 750 000 d is 1 3 for this reach of the fault defined as a 30 km wide band about a main fault trace for that part near parkfield which could be associated with the nucleation of the 1857 earthquake d is 1 1 at this same scale d is 1 4 for the san andreas and related faults near san bernardino where the 1857 rupture stopped compared to 1 2 for the san andreas san juan fault segments near the point of arrest of the 1966 parkfield earthquake at finer map scales 1 24 000 and 1 62 500 critical lengths of 500 m and 1 km are identified which might relate to the extent of off san andreas fault offsets the critical lengths also suggest that fault geometry is not self similar if this fractal geometry persists through the seismic cycle it may be possible to use a quantitative measure of complexity to explain the occurrence of great and characteristic earthquakes along a given reach of fault

fin whale tracks recorded by a seismic network on the juan de fuca ridge northeast pacific ocean fin whale calls recorded from 2003 to 2004 by a seafloor seismic network on the endeavour segment of the juan de fuca ridge were analyzed to determine tracks and calling patterns over 150 tracks were obtained with a total duration of 800 h and swimming speeds from 1 to 12 km h the dominant inter pulse interval ipi is 24 s and the ipi patterns define 4 categories a 25 s single ipi and 24 30 s dual ipi produced by single calling whales a 24 13 s dual ipi interpreted as two calling whales and an irregular ipi interpreted as groups of calling whales there are also tracks in which the ipi switches between categories call rates vary seasonally with all the tracks between august and april from august to october tracks are dominated by the irregular ipi and are predominantly headed to the northwest suggesting that a portion of the fin whale population does not migrate south in the fall the other ipi categories occur primarily from november to march these tracks have slower swimming speeds tend to meander and are predominantly to the south the distribution of fin whales around the network is non random with more calls near the network and to the east and north

fe ti v p ore deposits associated with proterozoic massif type anorthosites and related rocks abstract magmatic rocks containing economic concentrations of iron titanium vanadium and phosphorous are commonly associated with massif type anorthosites and related rocks this rock association is part of the anorthosite mangerite charnockite rapakivi granite suites that are restricted to the proterozoic understanding the geochemistry and emplacement mechanisms of ilmenite magnetite and apatite ore deposits is crucial for exploration efficient mining operations and ore processing this review discusses the controlling factors on the grade of an ore its mineralogy and its major and trace element distribution we present petrogenetic models of currently mined deposits lac tio tellnes damiao and discuss the characteristics of minor ore bodies from anorthosite provinces worldwide grenville north china craton east european craton rogaland laramie models of formation of anorthosite and related rocks are presented as well as the nature of the possible parental magmas of the suite a mineralogical classification of fe ti ores is proposed 1 gabbro noritic ilmenite ore apatite magnetite 2 ti magnetite dominated ore 3 nelsonite fe ti oxides apatite and 4 rutile ilmenite ore the stability of ilmenite and magnetite is then critically reviewed and the influence of various factors particularly oxygen fugacity and crystallization pressure is examined we discuss liquidus compositions of fe ti oxides and the behavior of important trace elements such as cr and v both of which are sensitive to fo2 variations post cumulus evolution of both oxides can occur due to re equilibration with trapped liquid re equilibration with ferromagnesian silicates exsolution oxidation reaction between ilmenite and magnetite and metamorphic overprinting these various processes are described and their effects on the oxide geochemistry are emphasized several potential ore forming processes have been invoked and can explain the formation of huge concentration of ilmenite magnetite apatite fractional crystallization can be combined with crystal sorting and plagioclase buoyancy to produce relative enrichment of dense ore minerals silicate liquid immiscibility can segregate conjugate si rich and fe rich melts the latter being enriched in fe ti p magma mixing can produce hybrid magmas located in a single phase field of the phase diagram and precipitate a pure ilmenite cumulate alternative processes are also described such as ejection of fe ti enriched residual melts by filter pressing and compaction solid state remobilization of ilmenite in veins and hydrothermal transport of fe and ti from the host anorthosite followed by concentration in veins and lenticular ore bodies the magnetic properties of fe ti ore deposits present contrasting signatures depending on whether the natural remanent magnetization is dominated by hemo ilmenite or multi domain magnetite micro and macro scale deformation features of ore rocks are intimately correlated with magma emplacement and with ballooning of the anorthosite diapir associated with gravitational sagging of dense ore bodies exploration perspectives show that oxide apatite gabbronorites are interesting targets because ilmenite in these rocks is poorer in cr and mg and because the ti resource may be combined with apatite and vanadiferous magnetite

a granite gabbro complex from madagascar constraints on melting of the lower crust the ranomandry complex is a neoproterozoic nested intrusion from central madagascar composed of a gabbroic core within a coeval peraluminous granite ring intruding pelitic metasediments although xenocryst entrainment and magma mixing have both contributed to marginal phases of the granite the primary melt is characterised by steep lree hree ratios and negligible or slightly positive eu anomalies both isotopic and trace element systematics preclude an origin from either partial melting of the metapelitic country rock or from fractional crystallisation of the gabbroic magma however trace element modelling suggests an origin from the dehydration melting of a plagioclase poor garnet bearing metagreywacke at temperatures of 850 900 c and at lower crustal pressures 10 kbar melting of an enriched subcontinental mantle generated gabbroic magmas that caused advective heating and anatexis at the base of thickened continental crust during their ascent transport of the resulting granite magma was facilitated by the pre existing plumbing system that overcame thermal and mechanical problems associated with both diapirism and self propagating dykes as mechanisms for long distance transport of granite magmas the nested geometry of the intrusions is an indication of a structurally homogeneous lower crust that contains no pre existing shear zones or fault systems

simultaneous inversion for q and source parameters of microearthquakes accompanying hydraulic fracturing in granitic rock an inversion that fits spectra of earthquake waveforms and gives robust estimates of corner frequency and low frequency spectral amplitude has been used to determine source parameters of 223 microearthquakes induced by hydraulic fracturing in granodiorite assuming a 2 source model the inversion fits the p wave spectra of microearthquake waveforms to determine individual values of corner frequency and low frequency spectral amplitude for each event and one average frequency independent q for all source receiver paths we also implemented a constraint that stress drops of all microearthquakes be similar but not equal and found that this constraint did not significantly degrade the quality of the fits to the spectra the waveforms analyzed were recorded by a borehole seismometer the p wave q was found to be 1070 for q values as low as 600 and as high as 3000 the misfit between model and spectra increased by less than 5 per cent and the average corner frequency changed by less than 15 per cent from those obtained with a q of 1070 average stress drop was 3 7 bars seismic moments obtained from spectra ranged from 1013 to 1018 dyne cm the low stress drops are interpreted to result from underestimation of the actual stress drops because of a nonuniform distribution of stress drop and slip along the fault planes spatially varying stress drops and slips result from the strong rock heterogeneity due to the injection of fluid into the rock stress drops were found to be larger near the edges of the seismic zone in regions that had not been seismically active during previous injections the seismic moments determined from spectra were used to obtain a coda length to moment relation then moments were estimated for 1149 events from measurements of coda lengths from events whose moments could not be measured from spectra because of saturation or a low signal to noise ratio the constant of proportionality between cumulative number of events and seismic moment is higher than that found for tectonic regions the slope is so high that the seismic energy release is dominated by the large number of small events in the absence of information about the number of events smaller than we studied we cannot estimate the total seismic energy released by the hydraulic injection

source parameters of earthquakes recorded near the itoiz dam northern spain we calculate the source parameters and attenuation from earthquakes recorded near the itoiz dam from 2004 to 2009 with magnitudes ranging between 1 2 and 5 2 we use a genetic algorithm in order to fit the three component p wave spectra with the spectral level corner frequency and attenuation factor as searching parameters the obtained moments range from 1 72 1011 to 2 65 1015 nm the radii span from 0 09 to 1 00 km and the stress drops vary from 0 006 to 29 462 mpa the maximum value for the q attenuation factor is 794 and the minimum value is 53 we find a good agreement between empirical and theoretical relationships between moment and magnitude there seems to be a breakdown of self similarity but it could be due to the method used we group the data by means of a self organizing map and the clusters found are related by their magnitude and not by other considerations

source parameters of microearthquakes in southeastern sicily italy we computed the source parameters of 135 local earthquakes that occurred in southeastern sicily italy between 1994 and 2001 magnitudes ranged from 0 6 to 2 5 the source parameters were determined from the spectral analysis of p waves after corrections for attenuation and site effects p wave quality qp and site s factors are known in the two frequency ranges 3 9 hz and 16 27 hz giampiccolo et al 2003 because the correction for qp and s over the whole spectrum could not be performed a new approach to estimate spectral parameters was applied we defined the new notion of holed spectrum to specify a spectrum lacking corrected spectral amplitude values within a certain frequency range whereas we referred to a whole spectrum to specify when the entire analyzed frequency band was used a detailed statistical analysis showed that dealing with the holed spectrum did not lead to significant differences in the estimate of spectral parameters displacement holed spectra corrected by the attenuation and site response were then used to estimate source parameters seismic moments ranged from 1017 to 1020 dyne cm and source dimensions from 150 to 500 m in general the stress drop values obtained analyzing p wave spectra were very low because they mainly span the range of 0 05 5 bars

estimating range to a vocalizing fin whale using the timing and amplitude of multipath arrivals a semi automated method is described to range to vocalizing fin whales using the timing and amplitude of multipath arrivals measured on seafloor receivers calls are detected and multipath arrivals identified with a matched filter multipath times and relative amplitudes are predicted as a function of range by ray tracing because the direct and first water column multiple arrivals are not always observed different hypotheses for the observed arrival paths must be considered for two arrivals an amplitude threshold is used to determine if the first arrival is the direct path and if not the call is disregarded as distant when three or more arrivals are detected three hypotheses for the paths of arrivals are considered the solution is the hypothesis and range that minimizes the timing and optionally amplitude ratio or absolute amplitude residual the method is tested with data from two ocean bottom seismometers one on the juan de fuca ridge and the other in the cascadia basin solutions obtained by

sounds from airguns and fin whales recorded in the mid atlantic ocean 1999 2009 between 1999 and 2009 autonomous hydrophones were deployed to monitor seismic activity from 16 n to 50 n along the mid atlantic ridge these data were examined for airgun sounds produced during offshore surveys for oil and gas deposits as well as the 20 hz pulse sounds from fin whales which may be masked by airgun noise an automatic detection algorithm was used to identify airgun sound patterns and fin whale calling levels were summarized via long term spectral analysis both airgun and fin whale sounds were recorded at all sites fin whale calling rates were higher at sites north of 32 n increased during the late summer and fall months at all sites and peaked during the winter months a time when airgun noise was often prevalent seismic survey vessels were acoustically located off the coasts of three major areas newfoundland northeast brazil and senegal and mauritania in west africa in some cases airgun sounds were recorded almost 4000 km from the survey vessel in areas that are likely occupied by fin whales and at some locations airgun sounds were recorded more than 80 days month for more than 12 consecutive months

scaling of the shear rupture process from nucleation to dynamic propagation implications of geometric irregularity of the rupturing surfaces a series of systematic high resolution laboratory experiments have been performed on the nucleation of propagating slip failure on preexisting faults having different surface roughnesses to demonstrate how the size scale and duration of shear rupture nucleation are affected by geometric irregularity of the rupturing surfaces on the basis of the experimental results it has been discussed theoretically how consistently scale dependent physical quantities inherent in shear rupture are scaled the experiments led to conclusive results that the nucleation process consists of two phases phase i an initial quasi static phase and phase ii a subsequent accelerating phase and that the nucleation process is greatly affected by geometric irregularities on the rupturing surfaces in phase i the rupture grows at a slow steady speed which is independent of the rupture growth length l in contrast during phase ii the rupture develops at accelerating speeds v which increase with an increase in l obeying a power law v vs l c n where vs is the shear wave velocity c is the characteristic length representing the geometric irregularity of the fault surfaces and and n are constants 8 87 10 29 and n 7 31 scale dependency of scale dependent physical quantities including the nucleation zone size and its duration is commonly ascribed to scale dependency of the slip dependent constitutive law parameter dc which is in turn governed by c it has been discussed that a unified comprehension can be provided for shear rupture of any size scale if the constitutive law for shear rupture is formulated as a slip dependent law

real time reporting of baleen whale passive acoustic detections from ocean gliders in the past decade much progress has been made in real time passive acoustic monitoring of marine mammal occurrence and distribution from autonomous platforms e g gliders floats buoys but current systems focus primarily on a single call type produced by a single species often from a single location a hardware and software system was developed to detect classify and report 14 call types produced by 4 species of baleen whales in real time from ocean gliders during a 3 week deployment in the central gulf of maine in late november and early december 2012 two gliders reported over 25 000 acoustic detections attributed to fin humpback sei and right whales the overall false detection rate for individual calls was 14 and for right humpback and fin whales false predictions of occurrence during 15 min reporting periods were 5 or less transmitted pitch tracks compact representations of sounds allowed unambiguous identification of both humpback and fin whale song of the ten cases when whales were sighted during aerial or shipboard surveys and a glider was within 20 km of the sighting location nine were accompanied by real time acoustic detections of the same species by the glider within 12 h of the sighting time

source parameters of microearthquakes at mount st helens usa summary we estimate the source parameters for a selection of microearthquakes that occurred at mount st helens in the period 1995 1998 excluding the activity of 2004 september this time period includes the most intense episode of earthquake activity since the last dome building eruption in 1986 october 200 seismograms were processed to obtain seismic moments source radii stress drops and average fault slip the source parameters were determined from the spectral analysis of p waves after correction for attenuation and site effects in particular p wave quality qp and site s factors have been previously calculated in the frequency ranges 2 7 hz and 18 30 hz because it was impossible to perform corrections for qp and s over the whole spectrum we applied a new approach based on the notion of holed spectrum to estimate spectral parameters the term holed spectrum indicates a spectrum lacking corrected spectral amplitude values at certain frequencies we carried out a statistical study to verify that dealing with the holed spectrum does not lead to significant differences in the estimates of spectral parameters we also investigated the dependence of spectral parameters low frequency level corner frequency and high frequency decay on the bandwidth of spectral hole and defined the threshold values for three different spectral models displacement holed spectra corrected by attenuation and site response are then used to determine spectral parameters in order to calculate seismic source parameters seismic moments range from 1017 to 1019 dyne cm source dimensions from 100 to 350 m and average fault slip from 0 003 to 0 1 cm self similarity seems to break down in that stress drops are very low 0 1 1 bars we postulate that seismicity is associated with a brittle shear failure mechanism occurring in a highly heterogeneous material under a relatively low stress regime

microearthquake spectra from the anza california seismic network site response and source scaling abstract we analyzed spectra of local microearthquakes recorded by the anza california seismic network to isolate the effects of site response and to investigate the scaling of source parameters for small earthquakes spectra of microearthquakes m m o 19 dyne cm at anza have shapes characteristic of the receiver sites and are generally independent of the source region thus the site response is a major conditioner of the observed spectral shape to remove the effects of site response from the spectra of a m 3 event and isolate its source spectrum we divided by the spectra of an adjacent aftershock used as an empirical green9s function event the spectral ratios indicate that the apparent corner frequencies of small earthquakes m o 19 dyne cm observed at even the high f max stations on hard rock are much lower than the source corner frequencies the spectral ratios are consistent with stress drop remaining constant with decreasing seismic moment for events with moments as small as 10 18 dyne cm the spectral ratios display remarkable agreement between sites which showed vast differences in their original spectra indicating that the spectral division effectively removed the site response the source spectrum of the m 3 event has a high frequency spectral fall off of about 2 an apparent dependence of high frequency fall off with seismic moment in the original spectra can also be explained by the effects of site response the difference between the p and s wave corner frequencies and high frequency roll offs in the observed spectra for these events is the result of the site response and is not a source property the shapes of the spectra of microearthquakes at anza can largely be explained by attenuation at shallow depth with a frequency independent q for some sites near surface resonances are also apparent in the spectra of microearthquakes it is indicated by t values determined for each site that q p q s for the shallow low q layer further evidence of low near surface q is observed in the anomalous spectra of an unusually shallow earthquake source depth 1 km in the network the spectra from this shallow event are depleted in high frequency energy at most stations relative to those of deeper events this observation can be explained by a low q surficial zone for stations of the network situated on alluvium this low q layer has a maximum thickness of about 3 km and maximum p and s wave q values of 30 to 50

a comparative study on attenuation and source scaling relations in the kanto tokai and chubu regions of japan using data from hi net and kik net abstract attenuation relations are derived for central japan broadly spanning the kant tokai and chubu regions using recordings of small earthquakes 2 0 m jma 4 0 japan meterological agency magnitude and moderate to large magnitude earthquakes 3 0 m jma 7 2 we independently analyze data from both small magnitude and moderate to large magnitude earthquakes to provide an insight into the use of attenuation relations derived in regions of low seismic activity a strong correlation is found between the attenuation parameters derived from each dataset we find that q is strongly depth dependent and that apparent geometrical decay increases with increasing hypocentral distance this is modeled by using a three segment decay function with the initial decay forced to 1 r moment magnitudes are close to the published m jma magnitude but are on average slightly higher an increase in stress drop with magnitude is required in order to model both the small magnitude and moderate to large magnitude datasets alternatively we show that a constant stress drop model is suitable to model the response spectra of both small magnitude and moderate to large magnitude earthquakes when considering the saturation of the source corner frequency due to a static site filter such as f max or we test our ability to predict strong ground motion by using our attenuation and source scaling relations derived from the small magnitude recordings to stochastically simulate peak ground acceleration peak ground velocity and 5 damped response spectral ordinates over a range of magnitudes and distances the residuals of this simulation are found to be largely independent of distance and magnitude we compare our attenuation relations against other relations derived for japan the residuals of these relations are analyzed and compared against those obtained from the model found in this study we find that in this study the prediction of strong ground motions is possible using small magnitude data and that the validity of the prediction extends across all magnitudes available for comparison 2 0 m jma 7 8 on the other hand by using an alternative published predictive relation for japan derived using large magnitude events peak ground acceleration is significantly overestimated for small magnitude earthquakes

density distribution functions and correlations of earthquake parameters abstract the statistical analysis of the source parameters of 9 earthquake sets of different types aftershocks scattered events swarms and of different seismic regions shows that the density distribution function ddf of the linear dimension l of a fault is represented by a negative power law as well as the ddf of the static stress drop and of the scalar seismic moment mo it is then suggested and tentatively verified that also the ddf of the root mean square ground acceleration defined as a function of l and may be represented by a negative power law and that at least in the cases examined it scales like the ddf of it is seen that the variability of the static stress drop is significant from one region to another as is well known but it seems remarkable also in the same seismic region in particular in california varies by several orders of magnitude and in the different sets of events of a given region as observed again for california it is hypothesized that a correlation although weak between the stress drop and the linear dimension of a fault exists and the analyses seem not to contradict that may be a decreasing function of l finally it is suggested that the seismicity of a region may be represented two dimensionally as a function of the ddf of the stress drop and of the linear dimension of a fault instead of the classic b and bo values

seismotectonics of the hida region central honshu japan abstract seismotectonic features of the northern hida region central honshu japan have been investigated in some detail mainly on the basis of the last 6 years of observations of seismicity and focal mechanism of a large number of earthquakes with reference to the geological and tectonic setting and evidence of a large earthquake in the past it was found that high seismicity is concentrated with a remarkably clear lineation but with a relatively low activity in the central section along the atotsugawa fault extending for about 70 km this is one of major quaternary faults in this region the high seismicity with spatially nonuniform distribution may be related to postseismic stress concentration after the 1858 hida earthquake m 7 0 and to heterogeneous fault strength seismicity is also high with belt like extension beneath the hida mountain range which is the highest mountain system in the japan islands the depth distribution of seismicity is clearly bounded at 15 km below the atotsugawa fault and 8 km beneath the hida mountains the local variations can be interpreted as being due to the difference in the brittle ductile transition depth which suggests higher temperature beneath the mountains involving active volcanoes the focal mechanism solutions indicate that the maximum compressive stress is oriented in an ese wnw direction which is more consistent with the direction of motion of the pacific plate relative to the eurasian plate rather than the suggested relative motion between the north america and eurasian plates the magnitude of the shear stress working in this region is estimated to be less than 700 bar

scaling relations of earthquakes that occurred in the upper part of the philippine sea plate beneath the kanto region japan estimated by means of borehole recordings acceleration source spectra of sh waves for 94 interplate and 74 intraplate earthquakes with a moment range of m 0 10 13 10 18 n m are investigated using 634 strong motion records obtained at 27 borehole and 7 surface hard rock stations installed in the kanto region central japan different scaling relations control the estimated acceleration source spectra for interplate and intraplate events the estimated acceleration source spectra of interplate events are similar to the spectra expected from the barrier model and those of intraplate events show a characteristic bump around the corner frequency the amplitude of acceleration source spectrum of interplate events is on the whole larger than that of intraplate events for the same seismic moment seismic moment m 0 corner frequency f c and seismic energy e are evaluated from the estimated acceleration source spectrum for each earthquake the seismic moment m 0 is nearly proportional to f c 3 the ratio of seismic energy to seismic moment is e m 0 1 15 12 9 10 5 for all events without a significant difference between interplate and intraplate earthquakes this means that the estimated velocity source spectra for interplate and intraplate events with the same seismic moment are nearly identical the dependence of apparent stress a e m 0 on seismic moment is weak and depends on tectonic setting apparent stress drop 2 a is almost proportional to the brune9s stress drop

baleen whale distribution and seasonal occurrence revealed by an ocean bottom seismometer network in the western indian ocean abstract from the acoustic data acquired by the rhum rum reunion hotspot and upper mantle reunions unterer mantel ocean bottom seismometer obs network between october 2012 and november 2013 this study revealed baleen whale occurrence in the western indian ocean io low frequency songs from three species antarctic blue whales pygmy blue whales and fin whales as well as p calls or spot calls from an unknown species were recorded on the dataset the wide arrangement of the obs network 2000 km 2000 km provided valuable information to draw seasonal patterns of occurrence and distribution all over the area these species occurred sympatrically in the western io at least during austral autumn months emphasizing the importance of this region for these populations this data set helped to refine the knowledge on their spatio temporal distribution and complete the picture built by previous studies a tighter sub network of 8 obss deployed on the south west indian ridge provided ideal inter sensor spacing for whale tracking we demonstrated the capability of such array of detecting and tracking the three different whale species up to 50 km and for several hours as a result and to understand the effect of acoustic wave propagation songs from the tracking were described at a close and remote distance of the sensor this work could also help to understand the local behavior of these species during austral autumn months in this area of the western indian ocean

tracking fin whale calls offshore the galicia margin north east atlantic ocean data recorded during a temporary deployment of ocean bottom seismometers obss are used in this study to monitor the presence of fin whales around the array in the summer of 2003 ten obss were placed 250 km from the nw coast of iberia in the galicia margin ne atlantic ocean for a period of one month the recorded data set provided a large variety of signals including fin whale vocalizations identified by their specific acoustic signature the use of a dense array of seafloor receivers allowed investigation into the locations and tracks of the signal generating whales using a seismological hypocentral location code individual pulses of different sequences have been chosen to study such tracks problems related to the correct identification of pulses discrimination between direct and multiple arrivals and the presence of more than one individual have been considered prior to location fin calls were concentrated in the last two weeks of the deployment and the locations were spread around the area covered by the array these results illustrate that besides its classical seismological aim deployment of semipermanent seafloor seismic arrays can also provide valuable data for marine mammal behavior studies

high frequency borehole seismograms recorded in the san jcinto fault zone southern california part 2 attenuation and site effects we examine surface and downhole p and s wave spectra from local earthquakes recorded at two borehole seismometer arrays knw bh and pfo bh installed in the southern california batholith region of the san jacinto fault zone by the u s geological survey to assess the influence of the weathered layer on the spectral content of high frequency 2 to 200 hz seismic signals earthquake signals recorded downhole at both sites show significantly improved seismic bandwidth due to both a reduction in ambient noise levels and especially to dramatically increased levels of high frequency signal significant seismic signal is observed up to approximately 190 hz for p waves at knw bh stacked spectral ratios from these signals indicate that the highly weathered near surface between 0 and 150 m at knw bh and pfo bh exerts a much larger influence on seismic signals than deeper between 150 and 300 m material modeling of uphole downhole spectral ratio data suggests q 6 5 and q 9 between 0 and 150 m increasing to q 27 and q 26 between 150 and 300 m an outcrop mounted anza network station deployed approximately 0 4 km from knw bh displays roughly similar high frequency content to the knw bh downhole sensors but it exhibits spectra that are significantly colored by directional resonances low q and low velocity near surface material forms a lossy boundary layer at these borehole sites that is advantageous to the high frequency downhole environment not only are noise levels reduced but reflections from the surface and near surface are greatly attenuated as a result high frequency recordings from below the weathered zone more nearly resemble those recorded in a whole space than would otherwise be expected

anorthosites in the eastern granulites of tanzania new sims zircon u pb age data petrography and geochemistry several occurrences of anorthosites are known in the neoproterozoic mozambique belt in tanzania these are tectonically incorporated into a suite of enderbitic rocks and migmatitic orthogneisses of the eastern granulites two larger anorthosite bodies and associated rocks from the pare mountains and the uluguru mountains have been chosen for a comparative study regarding their formation age age of subsequent metamorphic processes mineral chemistry and rock chemistry all the investigated magmatic bodies were overprinted by neoproterozoic high pressure granulite facies metamorphism and deformation documented by similar petrography and mineralogy metamorphic textures and deformational characteristics however mineral chemistry geochemistry and geochronology reveal major differences between the two occurrences the pare anorthosite contains igneous zircons that yield archean formation ages of ca 2 64 ga and a more calcic mineral and rock chemistry that is typical for archean type anorthosites extremely narrow metamorphic rims around zircons could not be dated but may have grown during the neoproterozoic metamorphic overprint in contrast the uluguru anorthosite contains igneous zircon cores with u pb ages of 880 820 ma a broad metamorphic rim was dated at ca 640 650 ma the adjacent migmatitic basement gneisses yield formation ages of ca 986 ma followed by pb loss early neoproterozoic events can also be inferred from both anorthosite suite and basement samples of the mahenge mountains there u pb ages from zircon cores cluster around 730 800 ma well developed metamorphic rims yield neoproterozoic ages of 650 ma the basement gneisses are related to a destructive plate margin setting the anorthosites may have formed when parts of central madagascar rifted off east africa at the time considered