focal mechanisms of earthquakes related to the 29 november 1975 kalapana hawaii earthquake the effect of structure models initial focal mechanism determinations for the 29 november 1975 kalapana hawaii earthquake indicated discrepancy between the mechanism determined from teleseismic data by ando and the mechanism determined using data from the local u s geological survey network surrounding the epicenter region the resolution of this difference is crucial to correctly understand this earthquake as well as to understand the tectonics of the south flank of kilauea volcano when a model with a low velocity layer at the base of the crust is used for projection back to the focal sphere for the local network mechanisms the discrepancy vanishes to further investigate this result focal mechanisms were determined using several contrasting models for a set of well recorded earthquakes a large number of these earthquakes have mechanisms identical to the main shock when the low velocity layer model is used dispersion of p and t axes is also minimized by use of this model a low angle slip direction favored for the main shock and typical of most other solutions exhibits remarkable stability normal to the east rift zone of kilauea our results suggest a tectonic model similar in nature to that proposed by ando in which the south flank of kilauea consists of a mobile block of crust which is relatively free to move laterally on a low strength zone at about 10 km depth forceful injection of magma along the rift zones provides the loading stress which is released by catastrophic failure in the weak horizontal layer in a cycle of perhaps 100 yr

late quaternary stratigraphy glacial limits and paleoenvironments of the marresale area western yamal peninsula russia stratigraphic records from coastal cliff sections near the marresale station on the yamal peninsula russia yield new insight on ice sheet dynamics and paleoenvironments for northern eurasia field studies identify nine informal stratigraphic units from oldest to youngest the marresale formation labsuyakha sand kara diamicton varjakha peat and silt oleny sand baidarata sand betula horizon nenets peat and chum sand that show a single glaciation and a varied terrestrial environment during the late pleistocene the kara diamicton reflects regional glaciation and is associated with glaciotectonic deformation from the southwest of the underlying labsuyakha sand and marresale formation finite radiocarbon and luminescence ages of ca 35 000 to 45 000 yr from varjakha peat and silt that immediately overlies kara diamicton place the glaciation 40 000 yr ago eolian and fluvial deposition ensued with concomitant cryogenesis between ca 35 000 and 12 000 cal yr b p associated with the oleny and the baidarata sands there is no geomorphic or stratigraphic evidence of coverage or proximity of the yamal peninsula to a late weichselian ice sheet the nenets peat accumulated over the baidarata sand during much of the past 10 000 yr with local additions of the eolian chum sand starting ca 1000 yr ago a prominent betula horizon at the base of the nenets peat contains rooted birch trees ca 10 000 to 9000 cal yr old and indicates a 200 km shift northward of the treeline from the present limits corresponding to a 2 to 4 c summer warming across northern eurasia

stability limits of hydrous minerals in sediment and mid ocean ridge basalt compositions implications for water transport in subduction zones phase relationships in hydrated natural sediment and mid ocean ridge basalt morb compositions were investigated experimentally from 6 to 15 gpa and 700 c to 1400 c in order to determine the stability of hydrous phases in subducting slabs and to constrain reactions resulting in the release of water from subduction zones to the mantle phengite and hydrous aluminum silicates topaz oh and phase egg are stable in the sediment composition at depths greater than 150 km and constitute h2o reservoirs similarly lawsonite is an h2o reservoir in morb composition at depths greater than 150 km according to mass balance calculations based on experimental run products the weight proportions of phengite and h2o at 6 gpa in the sediment are about 50 and 2 respectively at pressures from 8 to 12 gpa topaz oh al2sio4 oh 2 appears as the hydrous mineral and the sediment retains about 0 5 0 7 wt h2o at higher pressures phase egg alsio3 oh appears as the hydrous phase with a large stability field the h2o content in the sediment is about 0 5 wt at pressures greater than 12 gpa in natural morb compositions lawsonite is the hydrous phase at pressures lower than 10 gpa about 1 wt h2o in the morb composition is retained by lawsonite at 6 gpa and 800 c above 6 gpa a lawsonite out reaction is controlled by compositional changes of garnet and clinopyroxene if the oceanic crust descends with an overlying sediment layer water can be carried down into the transition zone by the sediment the amount of transported water is controlled by the chemical compositions of the subducting sediments water in the morb layer can be stored to 300 km in lawsonite for a cold subduction zone geotherm water release at depths greater than 200 km through progressive lawsonite breakdown can hydrate the overlying mantle causing the generation of a peridotite region including hydrous phases chondrodite clinohumite phase a and phase e if this hydrous peridotite is dragged down by the descending oceanic crust water can be transported into the transition zone by the subduction process the amount of transported water is controlled by the thermal state of the slab and the chemical composition of morb

atmospheric radiocarbon calibration to 45 000 yr b p late glacial fluctuations and cosmogenic isotope production more than 250 carbon 14 accelerator mass spectrometry dates of terrestrial macrofossils from annually laminated sediments from lake suigetsu japan provide a first atmospheric calibration for almost the total range of the radiocarbon method 45 000 years before the present the results confirm the recently revised floating german pine chronology and are consistent with data from european and marine varved sediments and combined uranium thorium and carbon 14 dating of corals up to the last glacial maximum the data during the glacial show large fluctuations in the atmospheric carbon 14 content related to changes in global environment and in cosmogenic isotope production

the extent of the barents kara ice sheet during the last glacial maximum it has been a long standing discussion whether the barents kara ice sheet expanded onto mainland russia during the last glacial maximum lgm in this paper we describe many well dated by conventional and ams 14 c methods and optically stimulated luminescence sedimentary sequences in the controversial area of northern russia the sequences discussed are not covered by till and yet all predate the lgm the deposits consist mostly of aeolian or lacustrine easily deformable soft silt and fine sand two sites feature frozen mammoth carcasses and three sites contain palaeolithic artefacts and mammalian bones we emphasise that these formations show no sign of having been overridden by an ice sheet at several sites deposition of aeolian sediments and formation of ice wedges took place during the lgm time span these observations present unambiguous proof that the barents kara ice sheet did not cover mainland russia during lgm with a possible exception for the northern tip of the taimyr peninsula r 2001 elsevier science ltd all rights reserved

glacial and vegetation history of the polar ural mountains in northern russia during the last ice age marine isotope stages 5 2 abstract we describe and discuss the glacial and climate variations in the polar ural mountains in northern russia over the last 100 000 years a series of optically stimulated luminescence osl and radiocarbon ages from sediment cores demonstrate that there has been continuous deposition of lacustrine sediments throughout the last 65 ka in lake gerdizty a lake basin situated on the eastern foothills of the urals below the lacustrine sequence are two till beds the uppermost unit b was probably deposited by a large mountain centred glacier complex that covered the lake basin during marine isotope stage mis 4 this till bed might be a counterpart of the usa moraine in the western foothills of the polar urals which is dated with osl and 10 be cosmogenic nuclide methods to between 68 and 58 ka consistent with the osl ages from the lowermost lacustrine sediments in lake gerdizty during this glaciation some of the northern uralian outlet glaciers probably merged with the adjacent barents kara ice sheet that reached onto the adjacent lowlands forming large ice dammed lakes on both sides of the ural mountains the equilibrium line altitude ela on the local ice cap was then at least 1200 m lower than at present the pollen stratigraphy in lake gerditzy reflects an open tundra and steppe like vegetation throughout mis 3 2 60 11 7 ka the first significant change in vegetation shown by an increase of dwarf shrub communities of salix and betula took place during the lateglacial at around 15 ka or shortly after birch and spruce trees approached the area for the first time soon after the holocene transition 11 7 ka and became dominant elements in the vegetation after a few hundred years our reconstruction suggests a very cold summer climate during mis 4 and presumably also during the preceding mis 5b 95 85 ka glaciation probably amplified by the large ice dammed lakes that existed during these two glaciations a somewhat milder climate prevailed during mis 3 60 25 ka but a treeless vegetation nevertheless suggests that mean summer temperatures did not exceed 10 12 c before the earliest holocene

aqueous fluid connectivity in pyrope aggregates water transport into the deep mantle by a subducted oceanic crust without any hydrous minerals abstract the effect of pressure and temperature on the dihedral angles of aqueous fluid in a pyrope matrix was investigated experiments were performed on an h 2 o pyrope system in a multianvil apparatus over the pressure and temperature ranges of 4 13 gpa and 900 1200 c respectively the dihedral angle of the fluid in contact with the pyrope exhibited a significant change at pressures around 8 9 gpa the dihedral angles increased with increasing pressure up to 9 gpa at pressures above 9 gpa the dihedral angles were greater than 60 at temperatures below 1000 c therefore the efficient percolation of aqueous fluid in a pyrope matrix is not feasible in the upper mantle and the transition zone the fluid released from the breakdown reactions of the hydrous minerals lawsonite and phengite exists in the oceanic crust which mainly consists of garnet in the upper mantle and transition zone we conclude that a part of the aqueous fluid released from the hydrous minerals may be retained in the subducted oceanic crust and transferred into the deep mantle by the subduction process

stability of a hydrous δ phase alooh mgsio2 oh 2 and a mechanism for water transport into the base of lower mantle abstract the global water cycle in the earth is one of the most important issues in geodynamics because water can affect the physical and rheological properties of the mantle however it is still a matter of debate whether water can be transported into the lower mantle and core here we report a new reaction between aluminous perovskite and water to form alumina depleted perovskite and hydrous phase alooh mgsio2 oh 2 along the mantle geotherm in the lower mantle chemical analysis of the coexisting phases showed that the perovskite and post perovskite phases were depleted in al2o3 whereas hydrous phase contains at least 44 mol of mgsio2 oh 2 component at 68 gpa and 2010 k and 23 mol of this component at 128 gpa and 2190 k the present experiments revealed that hydrous phase alooh mgsio2 oh 2 can coexist with alumina depleted mgsio3 perovskite or post perovskite under the lower mantle conditions along the slab geotherm thus this hydrous phase in the slabs can transport water into the base of the lower mantle

inversion for source parameters from sparse data sets test of the method and application to the 1951 m 6 9 kona hawaii earthquake we have tested a method originally developed by beisser et al 1990 to retrieve the source parameters strike dip rake and depth of sparsely recorded earthquakes from the inversion of teleseismic waveform data the complete wave train of all body waves is modeled using the reflectivity method the parameter space of strike dip and rake is searched to find the source orientation which leads to the minimum misfit between the observed and the synthetic seismogram the 1983 kaoiki hawaii earthquake ms 6 6 was chosen as a test case the inversion of the full data set 16 stations gave a fault plane solution similar to the best double couple moment tensor solution of harvard university and national earthquake information centre these three solutions were averaged to create a standard solution sparse data sets were simulated by decimating the full data set and the resulting fault plane solutions were compared with the standard we found that as few as one to three stations were sufficient to retrieve the focal mechanism of the 1983 kaoiki event we applied this technique to the 1951 kona hawaii earthquake ms 6 9 a total of four stations and nine components were used to model the source parameters of this earthquake the depth was estimated at 13 3 km the fault plane solution was a decollement type with a near horizontal plane dipping at about 15 to the southwest and a near vertical plane striking nw se this observation supports a tectonic model for the kona coast similar to that of kilauea s south flank the upper crust is pushed away from the center of hawaii slipping westward along a near horizontal plane of weakness

the 1973 hawaii earthquake a double earthquake beneath the volcano mauna kea summary the 1973 hawaii earthquake occurred north of hilo at a depth of 40 to 50km the location was beneath the east flank of mauna kea a volcano dormant historically but active within the last 4000 yr aftershocks were restricted to a depth of 55 35km the event and its aftershock sequence are located in an area not normally associated with the seismicity of the mauna loa and kilauea calderas the earthquake was a double event the epicentres trending ne sw the events were of similar size and faulting mechanism the fault plane solutions obtained by seismic waveform analysis are a strike slip fault striking ew and dipping 55 s the auxiliary plane a ns vertical plane with a faulting plunge of 35 the axis of maximum compressive stress is aligned with the direction of the gravity gradient associated with the island of hawaii the fault plane striking ew parallels a surface feature the mauna kea east rift zone the earthquakes were clearly not associated with volcanic activity normally associated with mauna loa and kilauea and may indicate a deep seated prelude to a resumption of activity at mauna kea

vegetation and climate history in the laptev sea region arctic siberia during late quaternary inferred from pollen records abstract paleoenvironmental records from a number of permafrost sections and lacustrine cores from the laptev sea region dated by several methods 14 c ams tl irsl osl and 230 th u were analyzed for pollen and palynomorphs the records reveal the environmental history for the last ca 200 kyr for interglacial pollen spectra quantitative temperature values were estimated using the best modern analogue method sparse grass sedge vegetation indicating arctic desert environmental conditions existed prior to 200 kyr ago dense wet grass sedge tundra habitats dominated during an interstadial ca 200 190 kyr ago reflecting warmer and wetter summers than before sparser vegetation communities point to much more severe stadial conditions ca 190 130 kyr ago open grass and artemisia communities with shrub stands alnus fruticosa salix betula nana in more protected and moister places characterized the beginning of the last interglacial indicate climate conditions similar to present shrub tundra alnus fruticosa and betula nana dominated during the middle eemian climatic optimum when summer temperatures were 4 5 c higher than today early weichselian sparse grass sedge dominated vegetation indicates climate conditions colder and dryer than in the previous interval middle weichselian interstadial records indicate moister and warmer climate conditions for example in the interval 40 32 kyr bp salix was present within dense grass sedge dominated vegetation sedge grass artemisia communities indicate that climate became cooler and drier after 30 kyr bp and cold dry conditions characterized the late weichselian ca 26 16 kyr bp when grass dominated communities with caryophyllaceae asteraceae cichoriaceae selaginella rupestris were present from 16 to 12 kyr bp grass sedge communities with caryophyllaceae asteraceae and cichoriaceae indicate climate was significantly warmer and moister than during the previous interval the presence of salix and betula reflect temperatures about 4 c higher than present at about 12 11 kyr bp during the allerod interval but shrubs were absent in the younger dryas interval pointing to a deterioration of climate conditions alnus fruticosa betula nana poaceae and cyperaceae dominate early holocene spectra reconstructed absolute temperature values were substantially warmer than present up to 12 c shrubs gradually disappeared from coastal areas after 7 6 kyr bp when vegetation cover became similar to modern a comparison of proxy based paleoenvironmental reconstructions with the simulations performed by an earth system model of intermediate complexity climber 2 show good accordance between the regional paleodata and model simulations especially for the warmer intervals

warm stages in the west siberian late pleistocene abstract the revised study of stratotypes and key sections of the karginsky regiostage in the west siberian plain with the use of 230th u dating determinations and advanced 14c dating indicated that many 14c ages obtained in the 1960 1970s were incorrect and revealed the pre karginsky age of the karginsky regional substage stratotypes adopted in the modern pleistocene stratigraphic schemes of west siberia the available 230th u and 14c data along with the new paleobotanical record provided substantial refinement of the late pleistocene succession of paleoclimatic events in the west siberian plain the 5e5 and 5e1 optima corresponding to climatic events of the greenland ice core and 5e2 and 5e4 pessima are revealed in boreal west siberia the obtained 230th u dating determinations even with their wide tolerance interval make it possible to recognize not only the major but certain minor climatic events within the kazantsevsky interglacial in boreal west siberia beds corresponding to mis 5c are recorded in the middle reaches of the ob river the preceding cooling was comparable with that of the later stages of the zyryansky glaciation and is correlated with mis 5d which suggests the beginning of the zyryansky glaciation occurred in the second half of mis 5 the obtained records do not require elimination or reducing of the range of the karginsky regiostage however the stratotypes of its regional sub stages chosen mainly in the 1960 1970s appear to be invalid

middle weichselian environments on western yamal peninsula kara sea based on pollen records pollen data from two sections from a coastal cliff on the western yamal peninsula 69 43 27vn 66 48 80ve document the environmental history during the karginsky middle weichselian interstadial low pollen concentrations high amounts of redeposited pollen and relatively high presence of artemisia pollen characterize sediments deposited at about 33 000 14 c yr b p grass sedge plant associations with few other herbs occupied the area during the late karginsky interstadial artemisia pollen may indicate rather xerophytic vegetation and disturbed soils in the area the dominance of redeposited pollen reflects scarce disturbed vegetation cover and low pollen productivity the climate was relatively cold and dry sediments dated to 32 400 14 c yr b p contain fewer redeposited pollen and concentration of non redeposited pollen is significantly higher pollen contents indicate the dominance of tundra like grass sedge vegetation and more humid conditions pollen records dated between 30 100 and 25 100 14 c yr b p also reflect scarce tundra like vegetation during this interval the presence of betula nana and salix pollen may reflect limited presence of shrub communities this suggests that the climate was somewhat warmer during the latter part of the interstadial however generally the pollen records show that harsh environmental conditions prevailed on the yamal peninsula during the karginsky interstadial

water transport into the deep mantle and formation of a hydrous transition zone abstract the phase relations in the peridotite water system to the top of the lower mantle reveal that a certain amount of water can be transported and stored in the transition zone by various hydrous minerals resulting in formation of a hydrous transition zone results of preliminary experiments to clarify the effect of water on kinetics of the olivine wadsleyite transformation are given and show that water enhances the transformation kinetics significantly there are potential dehydration sites in the deep mantle four sites along the descending slabs depending on their temperature profiles i e the mantle wedge of the subduction zone mantle transition zone top of the lower mantle where hydrous ringwoodite and superhydrous phase b decompose and deep in the lower mantle around 1200 1500 km depth where decomposition of phase d g occurs we also expect one site of dehydration melting at the base of the upper mantle where the hot mantle plume hydrated in the transition zone can be dehydrated the transition zone can serve as a water absorber for the mantle scale water circulation system some of the recent seismic works including the p wave tomography images reveal the existence of low velocity anomalies in the transition zone suggesting possibly a wet transition zone elevation of the 410 km discontinuity and lack of clear evidence for a metastable olivine wedge in cold slabs may be consistent with the equilibrium phase transformation from olivine to wadsleyite in cold and wet slabs on the basis of our kinetic study of the transformation under wet conditions

aluminous hydrous mineral δ alooh as a carrier of hydrogen into the core mantle boundary 1 in situ x ray diffraction experiments were conducted to determine the stability field of the aluminous hydrous mineral alooh over the entire conditions of the lower mantle we observed alooh at pressures from 33 to 134 gpa at 1350 2300 k indicating that this hydrous mineral in the sediment layer of a subducting slab could transport hydrogen into the core mantle boundary cmb

paleomagnetic constraints on fault motion in the hilina fault system south flank of kilauea volcano hawaii movement of the south flank of kilauea volcano in hawaii has been associated with catastrophic landslide events the surface expression of this former movement is the hilina fault system with fault scarps as high as 500 m paleomagnetic directions for lava flows exposed in the hilina fault scarps at puu kapukapu and keana bihopa on the hilina pali are used to determine the average rate of movement along faults slip surfaces separating the two sections this paper reports results from two independent paleomagnetic studies within the hilina pali area twenty one paleomagnetic sites 143 cores were sampled by the michigan technological university group from lava flows between the mo o ash and middle pohakaa ash at keana bihopa in the footwall block of the 500 m high hilina pali fault scarp thirty paleomagnetic sites 152 cores were collected by the california institute of technology group from lava flows between the mo o ash and middle pohakaa ash in the 300 m high puu kapukapu section the hanging wall block a comparison of site mean directions show that lava flows in the lower part of the puu kapukapu section have been tilted more than lava flows in the upper part with respect to the keana bihopa section the systematic steepening of remanent directions downsection at puu kapukapu indicates that slippage of this block occurs along listric normal faults the average amount of backward tilt of the puu kapukapu block based on a comparison of mean directions from the two sections is 7 8 7 7 using slope stability methods the average rate of movement of the puu kapukapu block since deposition of the middle pohakaa ash is 1 7 2 4 cm yr and the average displacement subsidence is 680 740 m assuming that the average displacement resulted from a series of earthquakes producing subsidence equal to that observed in the 1975 kalapana earthquake 3 m of subsidence along a 40 km segment of coastline on the south flank of kilauea volcano one kalapana size earthquake occurring every 200 years would account for this displacement lastly overall mean directions for the two sections indicate that puu kapukapu has rotated counterclockwise with respect to the hilina pali by 14 8 8 5 about a nearby vertical axis this also suggests that slippage between the two blocks occurs along listric normal faults

comment on a single force model for the 1975 kalapana hawaii earthquake by holly k eissler and hiroo kanamori

regional variation of the short period 1 to 10 second source spectrum we determined m b the body wave magnitude calculated from the maximum amplitude of short period p waves of 38 large earthquakes in various tectonic provinces the data are divided into three groups group 1 subduction zone thrust events group 2 nonsubduction zone dip slip and oblique slip events and group 3 strike slip events groups 2 and 3 include intraplate earthquakes comparison of m b values for these three groups of events suggests that the source spectral amplitudes of intraplate events at a period of about 1 4 sec is 2 to 5 times larger than those of subduction zone events with the same m w we also determined the source spectra of 28 large earthquakes m w 6 5 to 7 7 directly from global digital seismographic network gdsn data over a period range from 1 to 10 sec at periods from 1 to 2 sec the source spectral amplitudes of intraplate earthquakes are 2 to 4 times larger than those of subduction zone events with the same m w the difference decreases as the period increases to 10 sec

late quaternary stratigraphy of western yamal peninsula russia new constraints on the configuration of the eurasian ice sheet ice sheet reconstructions for the last glacial maximum in northern eurasia range from nearly complete coverage by a contiguous marine based ice sheet to large unglaciated areas stratigraphic records from yamal peninsula russia provide new insight on the eastern limit of the eurasian ice sheet in the kara sea radiocarbon and infrared stimulated luminescence ages from coastal cliff sections date the emplacement of the kara diamicton as older than ca 40 ka reflecting regional glaciation ice wedge growth peat accumulation and eolian and fluvial deposition characterized the past 40 k y and do not support coverage of yamal peninsula by an ice sheet or proximity to a glacier margin thus the late weichselian eurasian ice sheet was largely confined to barents sea and its global sea level contribution is reduced to 7 m of sea level equivalent

correlation of upper pleistocene sediments in northern west siberia abstract a geochronometric database comprising 121 optically stimulated luminescence and 59 radiocarbon dates plus u th date on peat from 24 key sections in northern west siberia is presented and discussed these data have been obtained during russian norwegian joint research for the past 15 years and are augmented by reports on radiocarbon dated mammoth carcasses in west siberia together they provide the basis for revising the regional stratigraphic scheme and for correlation to the european quaternary chronostratigraphy and marine oxygen isotope record the geochronologic correlation of sedimentary formations across west siberia involves classical stratotypes of fluvial shallow limnic and temperate marine sediments of the karginsky horizon ca 130 ka which was previously attributed to mis 3 the older kazantsevo marine formation is thus assigned a middle pleistocene age the uppermost glacial sedimentary complex containing glacial ice was deposited by shelf based ice sheets between ca 100 and 60 ka bp the postglacial pleistocene sediments are mostly ice bound loess like deposits and sink hole silts containing numerous mammoth carcasses that are radiocarbon dated to between ca 42 and 25 ka bp there are no traces of glacial activity on the siberian plains during mis 2 a period for which palaeoclimatic proxies suggest a cold and dry environment this synthesis indicates that the prior usage of the siberian correlation horizons of kazantsevo and karginsky as equivalents of the eemian and middle pleniglacial is stratigraphically invalid

source spectra of great earthquakes teleseismic constraints on rupture process and strong motion short period body waves recorded at teleseismic distances from great earthquakes provide information about source rupture processes and strong motions first we examine mostly wwssn records of 19 earthquakes of moment magnitude m w of 6 5 to 9 5 four parameters are measured from the short period p wave train the maximum amplitude the period at maximum amplitude the time between the first arrival and when the maximum amplitude is attained and coda length an extension m b of the teleseismic magnitude m b is defined using the maximum amplitude of the entire short period p wave rather than the amplitude achieved in the first few p wave cycles a least squares fit to the data yields the following relationship between m b and m w m b 0 53 m w 2 70 for m w 6 5 to 9 5 the time from the first arrival until the maximum amplitude is achieved and the coda length are roughly proportional to m w but are further interpreted by a simple asperity model of the rupture process these data support that short period waves are on average generated preferentially in the same regions of the fault plane as long period waves with periods of 10 to 50 sec we analyze the spectra of short and intermediate period teleseismic gdsn records for seven earthquakes with m w s of 6 4 to 7 8 and hand digitized short period wwssn records of the 1971 san fernando earthquake significant differences exist between the spectra of different events due partly to variations in tectonic setting or seismic coupling using the digital data we also investigate the relationship between time domain amplitude and spectral amplitude for short period p waves from our empirical relation between spectral amplitude and time domain amplitude we estimate the spectral amplitudes implied by the m b data we compare our results to the 2 and gusev spectral models neither model can completely represent the data nevertheless we consider the 2 model a useful reference model for comparing different events the average source spectrum of six large events with m w 7 4 to 7 8 does not have the spectral structure suggested by gusev an application to strong motion modeling is presented in which a 1971 san fernando teleseismic short period record is summed up to simulate teleseismic records produced by five great earthquakes the summation procedure matches the moment of the event to be simulated and includes rupture propagation fault plane roughness and randomness the m b data provide an important constraint on the summation procedures thus constrained this summation procedure can be more confidently used with near field strong motion records as green s functions to predict strong motions from great earthquakes

age dependence of oceanic intraplate seismicity and implications for lithospheric evolution we have determined depths for 16 oceanic intraplate earthquakes using body wave modeling a data set composed of these and 11 other well constrained depths shows that the maximum depth of seismicity deepens with increasing lithospheric age and appears to be bounded by a 700 800 c isotherm the maximum depth to which intraplate earthquakes occur is approximately equal to the flexural elastic thickness but much less than the seismic thickness from surface wave dispersion the maximum faulting depth is consistent with the predictions of rapid weakening at high temperatures for dry olivine rheologies determined by experimental rock mechanics oceanic intraplate earthquakes can occur at greater depths and temperatures than has previously been reported for continental crustal events presumably because oceanic lithosphere is stronger at high temperatures both the number of earthquakes and the cumulative seismic moment decrease with lithospheric age the cause of this trend is unclear possibilities include nonrandom location of preexisting weak zones with respect to the age provinces fault strengthening with age or a decrease in the stress level a decrease in intraplate stress with age is opposite that expected from ridge push stresses which increase with age but may result either from thermoelastic stresses which are greatest in young lithosphere or near ridge stress concentrations due to local heterogeneities in the spreading process

late pleistocene and holocene vegetation and climate on the taymyr lowland northern siberia abstract pollen records from perennially frozen sequences provide vegetation and climate reconstruction for the last 48 000 14c years in the central part of taymyr peninsula open larch forest with alnus fruticosa and betula nana grew during the kargin middle weichselian interstade ca 48 000 25 000 14c yr b p the climate was generally warmer and wetter than today open steppe like communities with artemisia poaceae asteraceae and herb tundralike communities with dwarf betula and salix dominated during the sartan late weichselian stade ca 24 000 10 300 14c yr b p the statistical information method used for climate reconstruction shows that the coldest climate was ca 20 000 17 000 14c yr b p a warming allerod interstade with mean july temperature ca 1 5 c warmer than today occurred ca 12 000 14c yr b p the following cooling with temperatures about 3 4 c cooler than present and precipitation about 100 mm lower corresponds well with the younger dryas stade tundra steppe vegetation changed to betula nana alnus fruticosa shrub tundra ca 10 000 14c yr b p larch appeared in the area ca 9400 14c yr b p and disappeared after 2900 14c yr b p cooling events ca 10 500 9600 and 8200 14c yr b p characterized the first half of the holocene a significant warming occurred ca 8500 14c yr b p but the holocene temperature maximum was at about 6000 4500 14c yr b p the vegetation cover approximated modern conditions ca 2800 14c yr b p late holocene warming events occurred at ca 3500 2000 and 1000 14c yr b p a cooling little ice age took place between 500 and 200 14c yr ago

stability of hydrous silicate at high pressures and water transport to the deep lower mantle hydrous magnesium rich silicates play an important role in transporting water into the deep mantle when oceanic plates subduct as slabs but were thought to dissociate at pressures of 44 gpa in situ x ray measurements in conjunction with a multi anvil apparatus show that hydrous phases of magnesium rich silicate are stable under lower mantle conditions up to 50 gpa and may transport water to deeper layers of the mantle the presence of water strongly influences the structure composition and dynamics of the earth s deep mantle1 2 3 4 hydrous magnesium rich silicates play an important role in transporting water into the deep mantle when oceanic plates subduct as slabs the highest pressure form of such hydrous silicates phase d was reported to dissociate into an assemblage of nominally anhydrous phases plus water at pressures of about 44 gpa equivalent to 1 250 km depth5 in this way free water would be released in the middle region of the lower mantle which suggests that no water can reach the deeper regions of the lower mantle here we use in situ x ray measurements in conjunction with a multi anvil apparatus using sintered diamond anvils to show that hydrous phases are stable under lower mantle conditions up to 50 gpa we found that phase d transforms to an assemblage with another hydrous silicate mgsih2o4 named phase h at pressures above about 48 gpa our results suggest that phase h is the dominant hydrous silicate in descending slabs and may be found at depths far deeper than 1 250 km we conclude that a significant amount of water is retained in the descending slabs and may be delivered to the deepest part of the lower mantle

depth estimates of large earthquakes on the island of hawaii since 1940 although hypocenters of earthquakes on the island of hawaii are now routinely assigned to within 5 km depth was a poorly determined parameter until the early 1960 s however the 1950 1960 period was very active both in volcanic eruptions and large earthquakes source depths for the 12 largest hawaiian earthquakes magnitude 6 or greater since 1940 are estimated from the ratios of body and surface wave amplitudes recorded at pasadena california excitation functions for rayleigh waves are calculated as a function of source depth for the two dominant periods in the pasadena records 8s and 20s theoretical body wave amplitudes are determined from synthetic seismograms calculated ratios are very sensitive to source depth for example amplitudes of 8 s rayleigh waves diminish by a factor of 300 between depths of 10 km and 50 km this is a much larger effect than the fault geometry which we estimate to be a factor of 4 between representative focal mechanisms estimated depths for post 1960 earthquakes agree fairly well with the instrumental depths in general large earthquakes near the volcanic flanks and fault systems are shallow 20 km two earthquakes of magnitude 6 occurred under the volcanoes mauna loa in 1950 and kilauea in 1951 they preceded major eruptions by 3 days and 14 months respectively and had the largest depth estimates at 40 55 km and 35 50 km ms values assigned from global amplitudes are compared with those assigned from pasadena amplitudes alone for 70 events in 1973 1974 with 5 1 m s 6 0 the global values are only slightly larger 0 05 magnitude units than the pasadena values indicating that pasadena amplitudes are on the average representative of the event magnitude

source characterization of two reykjanes ridge earthquakes surface waves and moment tensors p waveforms and nonorthogonal nodal planes well constrained fault plane solutions from p wave first motions for mid ocean ridge normal faulting earthquakes usually require nonorthogonal nodal planes local structural effects and or departures from a double couple source mechanism have been invoked to explain this phenomenon in order to obtain an independent determination of the source mechanisms for the april 24 1970 and april 3 1972 events on the southern reykjanes ridge we invert the rayleigh wave radiation pattern to obtain the source moment tensor the moment tensor formulation should be particularly well suited to this problem because it is not restricted a priori to a double couple source mechanism a potential drawback of the technique however is the requirement that phase velocities along the earthquake station paths be known very accurately in order to obtain the source phase from the observed phase and an objective of this study was to determine whether a regionalized phase velocity model compiled from published dispersion curves is adequate the results of the moment tensor inversion for both events indicate shallow normal faulting with the tension axis approximately horizontal and perpendicular to the local strike of the ridge apparent departures from a pure double couple source seem to result from errors in the data and the poor resolution of the mxz and myz components of the moment tensor for shallow sources after performing the inversion under a series of increasingly more stringent constraints we conclude that the data for both events are compatible with pure double couple sources with moments of 4 8 and 7 5 1024 dyn cm respectively we then show that interference between p pp and sp due to shallowness of the source can account for the observed nonorthogonality and match the observed p waveforms for the april 3 1972 event with theoretical seismograms calculated for a shear fault whose orientation is consistent with the surface wave solution the best fit to the data is obtained for a long narrow fault 13 km by 3 km with rupture initiating near the seafloor the moment indicated by the p waves is 7 5 1024 dyn cm these source parameters give an average displacement of about 60 cm and a stress drop of 30 60 bars taking into account various uncertainties although we might expect attentuation to be high in the mid ocean ridge environment the average attenuation required to fit the teleseismic data is not higher than normal t 1 s the p waves from the april 24 1970 earthquake were too small to be suitable for quantitative modeling by synthetic seismograms but are qualitatively consistent with a shallow fault model similar to that for the larger event we conclude that the faulting process described by these two earthquake mechanisms is directly related to the formation of rift valley topography

the postglacial pleistocene of the northern russian mainland abstract the paper summarizes the results of recent studies of late pleistocene postglacial geological events which occurred in the flatlands of northern russia stretching from the timan ridge to the laptev sea coast the available sedimentary record includes thawed and perennially frozen subaerial sediments and in places lacustrine and fluvial formations hundreds of geochronometric measurements by radiocarbon and luminescence techniques place this record within the time span of 50 11 ka bp which confirms an early mid weichselian age of the underlying glacial complex first established by the queen programme the spectrum of proxies includes sedimentary facies pollen data plant macrofossils oxygen isotope values megafauna remains insect assemblages traces of dna paleosols and permafrost properties together they indicate a continental progressively deteriorating climate with very cold winters and warmer than present summers through the second half of the late pleistocene minor climatic fluctuations are largely due to slightly changing humidity during mis 3 these changes are more pronounced in periglacial european russia in the vicinity of the barents kara ice sheet where the mid weichselian biotic maximum contrasts with conditions in the late weichselian polar desert in siberia the periglacial environments were more stable and beneficial for biota inspite of the increased continentality the recent data accumulated by various researchers are incompatible with the conventional correlation of the karginsky interglacial strata of siberia with mis 3 or any part of the european pleniglacial