distribution and mechanism of neogene to present day vertical axis rotations pacific australian plate boundary zone south island new zealand remarkably little knowledge exists about mechanisms of vertical axis rotation in continental crust steeply dipping basement rocks in south island new zealand provide an opportunity to map the distribution of rotations across the pacific australian plate boundary zone and to delineate boundaries of rotated blocks in unusual detail we synthesize new structural data with new and existing paleomagnetic data with geodetic data and with patterns of neogene quaternary faulting in the strike slip marlborough fault system for the past 20 m y vertical axis rotations have been hinged about two crustal scale boundaries near the east coast the ne hinge accommodated 50 of early middle miocene clockwise rotation which caused deformation of the eastern ends of the alpine wairau and clarence strike slip faults the sw hinge has accommodated a further 30 50 of finite clockwise rotation since 4 ma and deflects active fault traces the locus of rotation has shifted southwestward astride a subduction margin that is lengthening in that direction rotating rocks are pinned to the south against a locked collision zone where the continental chatham rise impinges against the margin slip on inland strike slip faults is transformed seaward across a zone of fault termination into rigid body rotation of a large continental block that has been thrust eastward over the downgoing subducted slab of the pacific plate the rotation mechanism is a migrating hinge which resembles a flexed telephone book strike slip faults are translated through a brecciated hinge region that does not coincide with a fixed material line in the rock

glaciers of the orulgan range assessment of the current state and possible development for the middle of the 21st century an assessment of the current state of orulgan range part of verkhoyansky range the ne siberia glaciers is proposed it was conducted involving aster images for the summer 2010 and the corresponding dem we have identified 70 of the glaciers outlined in the inventory of glaciers of the ussr part 2 orulgan range leningrad hydrometeoizdat 17 5 67 1972 the mean relative degree of the area reduction for orulgan glaciers is about 60 from that time up to 2010 using aster gdem the equilibrium line altitudes were defined for contemporary glacier systems of the orulgan we used climatic scenario for the period 2049 2060 which is an addition to the global temperature of 1 5 the array developed by institute of global climate and ecology ras and corresponding to this increase precipitation the array of voeikov observatory sankt peterburg identified by 31 aogcms involved in the cmip5 project in particular rcp4 5 to project the glacier development to 2049 2060 the previously developed technique used the outputs for assessing the evolution of the orulgan glacier systems results showed that under the scenario combination of precipitation feeding glaciers and summer temperatures the orulgan glaciation actually would disappear these results are compared with the earlier projection made involving the echam 4 as a climate scenario ananicheva et al cryosphere 4 435 445 2010

finite fault source study of the great 1994 deep bolivia earthquake we apply an empirical green s function method to recordings of teleseismic body waves from the june 9 1994 deep focus bolivia earthquake the far field source time functions reveal that rupture occurred on a sub horizontal fault plane the main rupture began some 25 km to the east of the hypocenter consists of three large subevents and covers a total area of about 60 40 km the static stress drop is quite large more than 150 mpa and the obtained rupture velocity is less than 2 km sec while the total dimensions of the earthquake are large compared to estimates of the width of a metastable olivine wedge at this depth the moment release is confined largely to a narrow band along an ew axis and may be compatible with phase transitions within a thickened slab core

characteristics of seismic radiation during the 1994 bolivian earthquake and implications for rupture mechanisms 1 the pkp waves of the 1994 deep bolivian earthquake mw 8 3 recorded by the dense short period seismic array in taiwan were used to make direct measurements of seismic source radiation employing array stacking technique those data were used to reconstruct the time function of the source rupture the well resolved frequency content of this source time function was from the period of 1 to 10 seconds and to resolve the rupture properties it provided source information at higher frequencies than that in previous studies from global seismic network data rupture time analysis identifies four asperities in the array observations and the initial rupture time of each asperity correlates well with results from previous studies using global network data the analysed results of this study also indicate that unlike other asperities the two major ones did not release as much high frequency energy however based on the limited broadband observations in taiwan the long period energy was normally released this study concludes that this can be well explained by the lubrication of fault during the great earthquake several deep earthquake mechanisms have been discussed for this special rupture characteristic and none may be fully ruled out

mantle phase changes and deep earthquake faulting in subducting lithosphere inclined zones of earthquakes are the primary expression of lithosphere subduction a distinct deep population of subduction zone earthquakes occurs at depths of 350 to 690 kilometers at those depths ordinary brittle fracture and frictional sliding the faulting processes of shallow earthquakes are not expected a fresh understanding of these deep earthquakes comes from developments in several areas of experimental and theoretical geophysics including the discovery and characterization of transformational faulting a shear instability connected with localized phase transformations under nonhydrostatic stress these developments support the hypothesis that deep earthquakes represent transformational faulting in a wedge of olivine rich peridotite that is likely to persist metastably in coldest plate interiors to depths as great as 690 km predictions based on this deep structure of mantle phase changes are consistent with the global depth distribution of deep earthquakes the maximum depths of earthquakes in individual subductions zones and key source characteristics of deep events

tectonic rotations about vertical axes during the last 4 ma in part of the new zealand plate boundary zone the declinations of the primary magnetization of sedimentary rocks in the northern part of the new zealand plate boundary zone after thermal or alternating field cleaning have been used to determine tectonic rotations about vertical axes of rigid crustal blocks the pattern of rotations during the last 4 ma combined with structural style and continuity defines seven structural domains each ca 100 100 200 km across which contain crustal blocks up to 100 km across and 20 km thick large crustal blocks tens of km across in two of these domains have rotated clockwise more than 20 relative to one of the margins of the plate boundary zone in the last 4 ma their behaviour appears to be controlled by the nature of the plate boundaries such as the presence of an underlying subducted slab and the strength of the crust at the back of the overlying crustal wedge small crustal blocks 10 km across may have rotated clockwise through angles greater than 20 during the last 4 ma floating on an underlying zone of more distributed deformation the tectonic rotations of the large crustal blocks and the nature of the deformation at their boundaries combined with an interpolation of the relative plate positions can be used to reconstruct the plate boundary zone at ca 4 ma

error analysis for the determination of tectonic rotation from paleomagnetic data appendix b is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington d c 20009 document b83 001 2 50 payment must accompany order recent determinations of tectonic rotation and flattening from paleomagnetic data have exaggerated the size of the confidence limits or error bars by about 25 this has been caused by the misuse of conventional error propagation formulas to derive one degree of freedom error bars from a two dimensional cone of confidence 95 an analytical calculation which is valid when error bars are small shows that the correct error bars are 75 to 80 of the values derived in previous studies i have used numerical integration to check on the applicability of the analytical solution and to calculate error bars when the analytical approximation cannot be used the analytical approximation may be used whenever 95 is less than 10 and the mean inclination is not too close to vertical confidence limits given for tectonic rotation and flattening in recent literature are too large and should be reduced by 20 25 narrowing the error bars in this way permits a more accurate interpretation of paleomagnetic data

a new self organizing mechanism for deep focus earthquakes the mechanism of deep focus earthquakes has been a puzzle since their discovery almost 70 years ago1 2 because brittle fracture and frictional sliding at depths in excess of 100 200 km would require unrealistic rock strengths3 4 rock strength does increase with pressure but a few hundred mpa equivalent to 10 20 km depth suffices to inhibit most fracture and elevated temperature activates ductile mechanisms that operate at stresses less than the fracture stength a range of mechanisms has been proposed for deep earthquakes including plastic instabilities5 7 shear induced melting8 11 and instabilities accompanying recrystallization12 13 or polymorphic phase transformation14 23 each of these proposed mechanisms has exhibited certain inherent weaknesses see kirby22 for review and discussion here we report experimental observations of high pressure faulting of metastable mg2geo4 olivine as it undergoes incipient transformation to a spinel 24 25 structure we present a model in which this faulting arises from the generation propagation and linking up of spinel filled anticracks26 when applied to the olivine spinel transformation in the earth s mantle the anticrack model27 satisfactorily accounts for the similarities and differences between shallow and deep earthquakes and removes the problems associated with frictional sliding

rupture characteristics of the deep bolivian earthquake of 9 june 1994 and the mechanism of deep focus earthquakes the m w 8 3 deep 636 kilometers bolivian earthquake of 9 june 1994 was the largest deep focus earthquake ever recorded seismic data from permanent stations plus portable instruments in south america show that rupture occurred on a horizontal plane and extended at least 30 by 50 kilometers rupture proceeded at 1 to 3 kilometers per second along the down dip azimuth of the slab and penetrated through more than a third of the slab thickness this extent is more than three times that expected for a metastable wedge of olivine at the core of the slab and thus appears to be incompatible with an origin by transformational faulting these large events may instead represent slip on preserved zones of weakness established in oceanic lithosphere at the earth s surface

geodetically determined strain across the southern end of the tonga kermadec hikurangi subduction zone summary a method of simultaneous reduction is presented for determining strain rates from multiple triangulation surveys where common triangulation stations have been used but the angles of the old survey have not necessarily been reobserved this method is applied to triangulation in the northern south island at the southern end of the tonga kermadec hikurangi subduction zone from a profile of shear strain across the indian pacific plate boundary the displacement of the indian plate relative to the pacific is calculated to be 54 9 mm yr at an azimuth of 84 f lo in remarkable agreement with the motion predicted by global plate tectonic models most of this motion occurs within a 15okm wide zone bounded on the east by the hikurangi trough within this zone the motion is partitioned near the hikurangi trough no slip is occurring at the upper surface of the subducting pacific plate the subduction thrust and motion is predominantly thrusting normal to the trough axis to the west is a region of predominantly dextral strike slip faulting this pattern is consistent with fitch s model of oblique subduction to the south of the profile a change is observed in the azimuth of the faulting along a line which marks the southern extent of the subduction slab indicating the end of the partitioned motion

fast rise times and the physical mechanism of deep earthquakes earthquakes at depths of 300 km are similar to shallower events in that they are dominantly of double couple character1 implying that shearing motion has taken place at depth but because increased friction at these high pressures inhibits brittle fracture2 3 various other mechanisms related to phase transformations have been invoked to explain the occurrence of deep earthquakes4 10 as yet however no consistent differences have been found between the source characteristics of deep 300 km and intermediate depth 300km earthquakes2 11 13 here we report a systematic global survey of the rise times and stress drops of deep and intermediate earthquakes the rise time is defined as the time from rupture initiation to peak moment release rate when the rise times are scaled to the seismic moment release of the events their average is nearly twice as fast for events deeper than 450 km as for shallower events this difference may ultimately provide an experimental means of testing proposed mechanisms for the generation of deep seismicity

widespread remagnetizations and a new view of neogene tectonic rotations within the australia pacific plate boundary zone new zealand 14 ma 1 than the presently observed rate of 3 4 ma 1 which is only likely to be characteristic of the tectonic regime established since 1 2 ma these new results are consistent with both long and short term deformation on the hikurangi margin being driven by realignment of the subducting pacific plate with collision of the hikurangi plateau in the late miocene potentially being key to both the initiation of tectonic rotations and the widespread remagnetization of neogene sediments however accommodating faster more coherent rotation of the hikurangi margin in neogene reconstructions of the new zealand plate boundary region particularly in the late miocene remains a challenge

large tectonic rotations in a wide zone of neogene distributed dextral shear northeastern south island new zealand abstract the new zealand plate boundary zone in the northern part of south island new zealand comprises a series of active dextral strike slip faults referred to as the marlborough fault zone mfz which link oblique continental convergence farther south along the alpine fault to subduction of the pacific plate along the hikurangi margin new paleomagnetic data are presented which together with previous studies suggest coherent neogene clockwise rotation up to 130 about a vertical axis of crustal blocks in the mfz starting at 20 ma there is a striking correlation between the amount of observed rotation and the trend of mesozoic basement structures creating this part of the new zealand orocline in a zone of distributed dextral shear about 100 km wide which has persisted for about 20 ma in the southern part of the mfz crustal blocks appear to be on a scale of 1 10 km with boundaries that are subparallel to the basement strike this way deformation is accommodated by a combination of fault slip and rotation in a zone of more pervasive dextral shear resulting in coherent bending of the basement structure in the central part of the mfz this rotation appears to be that of elongate crustal blocks 50 km 10 km in size rotating 80 clockwise at an average rotation rate 4 ma in detail the rotation rate has decreased towards the present from 6 ma at 20 ma to

block rotation by strike slip faulting structural and paleomagnetic evidence geometric analysis shows that motion of sets of strike slip faults should cause block rotation otherwise the distorted fault domain would not fit with its surrounding the sense of the block rotation depends on the sense of fault slip and the spacing and orientation of the faults all of which can be obtained from structural data the predictions of the geometric model can then be independently tested by paleomagnetic measurements the model was tested in northern israel structural data reveal several domains of contemporaneous right and left lateral strike slip faults paleomagnetic measurements show that in a domain of nnw trending left lateral faults blocks rotated 23 3 8 2 clockwise and in a domain of right lateral faults blocks rotated 22 4 9 0 anticlockwise these results are in agreement with the prediction of the geometric analysis of the structure the combined results of the heterogenous deformation of the area resembles a pure shear which allows n s extension by about 1 3 in other domains rotations of 34 6 9 1 and 53 1 11 0 were found in their original orientation the left and right lateral faults intersected at angles of 60 70 enclosing the principal axis of shortening in accordance with theories of brittle failure as a result of block rotations this angle is now larger and may reach 110 the results demonstrate large block rotations in different senses in domains of strike slip faults the independent structural and paleomagnetic data can be interpreted within the framework of a simple geometric model northern israel is considered to be a good model for this efficient mechanism of intraplate deformation which is expected to occur in similar tectonic settings elsewhere

the depth dependence of earthquake duration and implications for rupture mechanisms the duration of rupture is a fundamental characteristic of earthquakes and is important for understanding the mechanics of faulting1 2 the complexity of the seismic source and the incoherence of the high frequency seismic wavefield often inhibit the identification location and timing of features in the later part of earthquake rupture here we sum many teleseismic records from regional seismic arrays producing an unusually clear depiction of the earthquake source at short periods by suppressing background noise and coda generated near the receivers the ending as well as the beginning of rupture is clearly identifiable for most earthquakes examined measurements of 130 large earthquakes show that near 100 km depth rupture duration averages 11 s when scaled to a moment of 1026 dyn cm this decreases to 5 5 s at 650 km depth models of faulting suggest that duration should be inversely proportional to the shear wave velocity and the cube root of stress drop thus to explain the observed twofold decrease in duration with depth stress drops would have to increase by a factor of four as shear velocity increases with depth by only about 20 however observed stress drops show no strong trend with depth3 4 suggesting that the faulting process changes with depth

geodynamic implications of paleomagnetic data from tertiary sediments in sakhalin russia nw pacific 1 n s trending right lateral strike slip faults which were active in the tertiary transect sakhalin russia while mesozoic forearc and accretionary rocks testify to an earlier period of subduction several kinematic models have been proposed for the region but the details required to constrain these models such as the timing of the transition from subduction to strike slip tectonics in sakhalin are still unknown even first order tectonic features such as the boundaries of the plates with which sakhalin evolved during the tertiary are poorly known paleomagnetic results from around sakhalin were obtained to constrain the geodynamic evolution of the region comparison of paleomagnetic inclination data with the apparent polar wander paths for the eurasian pacific and north american plates suggests that sakhalin probably evolved with the north american plate although a history including the eurasian plate cannot be ruled out paleomagnetic declination data suggest that significant clockwise vertical axis rotation has occurred in sakhalin since the mid paleocene it is likely that this rotational deformation was accommodated by tertiary activity on right lateral strike slip faults which may be associated with the opening of the japan sea tatar strait and kuril basin these data contradict a published kinematic model for eastern sakhalin where counterclockwise vertical axis rotations were predicted for neogene basins in the east sakhalin mountains agreement is better however with published paleomagnetic data from southern sakhalin where clockwise vertical axis rotations were documented

nival glacial dynamics of geosystems in eastern siberia russia for the last 50 years it is presented the results of studying of small glaciers located in the eastern siberia along transect the kodar mountains baikalskiy and barguzinskiy ridges the eastern sayan mountains some glaciers from this transect have not been described before the inventorying of these glaciers is based on high resolution satellite images and fieldworks the most numbers of glaciers are located in the kodar mountains and few are in the baikalskiy and the barguzinskiy ridges most likely these glaciers remained mainly due to coldest winters and geomorphologic features the main parameters of a glacier s data the dynamics the current state cartographic representation remote sensing data and others are selected by analogy of the international glaciological database

tectonic rotation about the termination of a major strike slip fault marlborough fault system new zealand the marlborough fault system comprises a series of major right lateral strike slip faults that link the alpine fault to the hikurangi subduction zone in the pacific australia plate boundary zone in new zealand all of the major active faults of the marlborough fault system have continuous traces except for the clarence fault which terminates abruptly near the ward syncline paleomagnetic data from upper miocene and lower pliocene sedimentary rocks between the marlborough faults indicate a consistent post early pliocene regional clockwise rotation of about 20 an additional rotation of about 10 is evident at many localities near the termination of the clarence fault it is proposed that the additional rotation relative to the rest of the region is caused by a velocity gradient that likely exists between the active awatere fault and the termination of the clarence fault the existence of such a velocity gradient is consistent with inferences from geodetic strain data which suggest that one third of the displacement in the marlborough fault system occurs between the awatere and clarence faults the kinematics of rotation can be modelled by treating the area as a rigid block that pivots about the termination of the clarence fault the block rotation model satisfies field constraints on the styles of deformation observed at the boundaries of the block and is consistent with available paleomagnetic and geodetic data

glacier fluctuation in northern and high asia historical and methods perspective glaciers in asia occupy nowadays much smaller extents than those of the pleistocene but they still play an important role in alpine ecosystems e g shahgedanova 2002 glaciers also pose hazards to society and infrastructure with avalanches and glacial lake outburst floods being the most destructive of glacier related natural events richardson and reynolds 2000 jansk et al 2010 nie et al 2013 wang and zhang 2014 since the end of the little ice age lia glaciers have been retreating almost everywhere around the world and this process has dramatically accelerated during the recent decades fig 1 wgms 2013 however individual glaciers are behaving differently and some have advanced while most have been in retreat ipcc 2013 yao et al 2012 mountain glaciers are sensitive indicators of climate change e g dyurgerov and meier 2000 haeberli et al 2004 and to fully understand the connection between changing climate and glacier fluctuations all the variables of the glacier mass balance need to be assessed at the local and regional scale dowdeswell et al 1997 oerlemans 2005 one of the regions where information about glacier changes is still scarce is northern and high asia fig 1 largely because glaciers of the region are located relatively far from human settlements and some have only been found after the 1940s for example ivanov et al 2015 have provided the first inventory of glaciers in the barguzinsky ridge east of lake baikal russia in this issue at the same time continental glaciers of northern and high asia are located far from the main sources of moisture and are thus sensitive to climate change fujita 2008 kaser et al 2010 in this issue we have collected information about glaciers situated along a southwestnortheast transect from 77 e 32 n the western himalaya india to 128 e 65 n the orulgan range russia fig 2 and fed from different sources of moisture the north atlantic the arctic and the indo pacific air masses because glaciers in our focus area belong to different climate systems their systematic study across the whole region has the potential not only to assess the climate change at local and regional scales but also to reveal climate change patterns at a larger continental scale the papers of this issue cover a variety of glacier related topics methods studies glacier inventories current glacier dynamics and paleo reconstructions and are based on a range of data such as satellite imagery synoptic maps biogeochemical proxies from proglacial lake bottom sediments and meltwater streams pollen and oxygen isotope records from snow ice cores and high resolution seismic reflection data

magnetostratigraphic chronology of late miocene to early pliocene biostratigraphic and oceanographic events in new zealand successions of uplifted shallow marine sediments in new zealand were among the first to provide evidence of latest miocene climatic deterioration and were also among the first onshore successions where late miocene to early pliocene magnetostratigraphic records were established a revised chronology of late miocene to early pliocene events has been determined from new magnetostratiigraphic results from two important successions at blind river and upton brook south island new zealand lat 41 45 s long 174 05 e magnetostratigraphic results from upton brook are the fast from strata containing the kapitean index mollusks and provide the first reliable estimate of the age of the tongaporutuan kapitean boundary a coherent chronology from blind river and upton brook indicates that two synchronous low sea level and cool paleoclimatic events occurred in the late miocene kapitean stage this inference is supported from other well known coeval successions in the new zealand region the revised new zealand chronology supports recent determinations from the mediterranean that indicate a two stage messinian salinity crisis and a 5 2 ma age for the miocene pliocene boundary data from new zealand the mediterranean and ocean cores around the world suggest that these latest miocene events are related to glacio eustatic sea level fluctuations a 6 05 ma age for the first occurrence datum of globorotalia conomiozea indicates that significant diachroneity exists in the placement of this datum between the southwest pacific and the mediterranean confirming the observation that g conomiazea is unsuitable for correlation between ocean basins

elastohydrodynamic lubrication of faults the heat flow paradox provides evidence that a dynamic weakening mechanism may be important in understanding fault friction and rupture we present here a specific model for dynamic velocity weakening that uses the mechanics of well studied industrial bearings to explain fault zone processes an elevated fluid pressure is generated in a thin film of viscous fluid that is sheared between nearly parallel surface this lubrication pressure supports part of the load therefore reducing the normal stress and associated friction across the gap the pressure also elastically deforms the wall rock the model is parameterized using the sommerfeld number which is a measure of the lubrication pressure normalized by the lithostatic load for typical values of the material properties slip distance and velocity the sommerfeld number suggests that lubrication is an important process if the lubrication length scales as the slip distance in an earthquake the frictional stress during dynamically lubricated large earthquakes is 30 less than the friction with only hydrostatic pore pressure elastohydrodynamic lubrication also predicts a decrease in high frequency 1 hz radiation above a critical slip distance of a few meters this prediction is well matched by the strong motion data from the 1999 taiwan earthquake the observed 2 orders of magnitude variation in scaled radiated energy between small m w 6 is also predicted by the lubrication model

directivity analysis of the deep bolivian earthquake of june 9 1994 the june 9 1994 deep bolivian earthquake m w 8 3 d 636 km occurred on a nearly horizontal rupture plane with an approximate area of 2000 km 2 the rupture plane is constrained by directivity analysis of the p wave displacement pulses recorded at local regional and teleseismic distances the fact that there are local recordings of the displacement provides a strong constraint on the vertical extent of faulting which is less than 10 km the moment release had at least four distinct episodes or subevents the best overall explanation for the subevents is rupture which initiates on the western margin of the fault plane propagates to the east and then continues bilaterally along a 350 azimuth with most of the moment release occurring to the north the apparent rupture velocity between subevents is very low approximately 1 2 km s

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

frictional melting during the rupture of the 1994 bolivian earthquake the source parameters of the 1994 bolivian earthquake magnitude m w 8 3 suggest that the maximum seismic efficiency was 0 036 and the minimum frictional stress was 550 bars thus the source process was dissipative which is consistent with the observed slow rupture speed only 20 of the locals wave velocity the amount of nonradiated energy produced during the bolivian rupture was comparable to or larger than the thermal energy of the 1980 mount st helens eruption and was sufficient to have melted a layer as thick as 31 centimeters once rupture was initiated melting could occur which reduces friction and promotes fault slip

bending within the axial tectonic belt of new zealand in the last 9 myr from paleomagnetic data abstract tongaporutuan stage late miocene 11 6 myr sedimentary rocks at two localities within the axial tectonic belt of new zealand have a direction of magnetisation in which the declination is 020 11 and 030 8 d 95 the directions of magnetisation in rocks of similar age outside the belt have a declination like that of the earth s present axial dipole 360 the clockwise deviation of the declination is inferred to indicate bending of the rocks within the zone of deformation between the pacific and indian plates due to the oblique convergence of these plates

paleomagnetic constraints on cenozoic deformation along the northwest margin of the pacific australian plate boundary zone through new zealand 1 new zealand straddles the boundary between the australian and pacific plates a zone of oblique continental convergence and transform motion the actively deforming region offers a unique opportunity to study the dynamics of deformation including vertical axis rotation of rigid blocks within a transcurrent plate boundary zone we present and interpret paleomagnetic data from three new and three previously published sites from the nw part of the south island nw nelson region where sedimentary strata dated between 36 and 10 ma overlie the crystalline paleozoic basement assemblages of the gondwana margin compared with reference directions from the australian apparent polar wander path none of the results provide evidence of post eocene vertical axis rotation this suggests that for the past 36 myr nw nelson has remained a strong coherent block that has moved as a contiguous part of the australian plate this is in marked contrast to the strongly rotated nature of more outboard accreted terranes to the east for example the hikurangi margin in the north island nw of the alpine fault and the marlborough region in the ne of the south island se of the alpine fault have both undergone diverse clockwise rotations of up to 140 since the early paleogene the nw tip of the south island seems to have acted as a rigid backstop relative to these more complex oroclinal deformations we infer that because of its relatively stiff bulk rheology it has not been drawn into the distributed plate boundary rotational deformation associated with the new zealand orocline

triple junction kinematics accounts for the 2016 mw 7 8 kaikoura earthquake rupture complexity the 2016 moment magnitude mw 7 8 kaikoura earthquake generated the most complex surface ruptures ever observed although likely linked with kinematic changes in central new zealand the driving mechanisms of such complexity remain unclear here we propose an interpretation accounting for the most puzzling aspects of the 2016 rupture we examine the partitioning of plate motion and coseismic slip during the 2016 event in and around kaikoura and the large scale fault kinematics volcanism seismicity and slab geometry in the broader tonga kermadec region we find that the plate motion partitioning near kaikoura is comparable to the coseismic partitioning between strike slip motion on the kekerengu fault and subperpendicular thrusting along the offshore west hikurangi megathrust together with measured slip rates and paleoseismological results along the hope kekerengu and wairarapa faults this observation suggests that the west hikurangi thrust and kekerengu faults bound the southernmost tip of the tonga kermadec sliver plate the narrow region around kaikoura where the 3 fastest slipping faults of new zealand meet thus hosts a fault fault trench fft triple junction which accounts for the particularly convoluted 2016 coseismic deformation that triple junction appears to have migrated southward since the birth of the sliver plate around 5 to 7 million years ago this likely drove southward stepping of strike slip shear within the marlborough fault system and propagation of volcanism in the north island hence on a multimillennial time scale the apparently distributed faulting across southern new zealand may reflect classic plate tectonic triple junction migration rather than diffuse deformation of the continental lithosphere

assessment of solute and suspended sediments acquisition processes in the bara shigri glacier meltwater western himalaya india various physico chemical parameters of meltwater samples from bara shigri glacier collected during 2012 2013 were analysed to understand the dissolved ion chemistry and solute acquisition processes regulating major ion chemistry of the study area ionic dominance of anions followed the trend as hco3 so4 2 cl no3 whereas ionic dominancy of cations varied as ca2 mg2 k na for both the years high share of ca mg in the total cations and also dominancy of ca mg over na k for both the years demonstrate that solute acquisition processes in the meltwater of bara shigri glacier are mainly governed by the weathering of carbonates the piper plot identified ca hco3 as the dominant water type followed by caso4 type of water in the study area the average value of partial pressure of carbon dioxide pco2 for meltwater of the bara shigri glacier was 10 2 6 atm in 2012 and 10 2 3 atm in 2013 and were higher than the pco2 value of atmosphere 10 3 5 atm it indicates that the meltwater is in disequilibrium with respect to the atmosphere contents of suspended sediment in the meltwater were 1432 mg l in july and 596 mg l in september 2012 whereas in 2013 suspended sediment contents were 1093 mg l in august and 425 mg l in september following discharge pattern of the bara shigri glacier we found that bara shigri and gangotri glaciers demonstrate the higher rate of regional melting

estimation of the rupture velocity and fault length of the 2004 sumatra andaman earthquake using a dense broadband seismic array in taiwan abstract the rupture process of the disastrous sumatra andaman earthquake of 26 december 2004 was analyzed by array processes for teleseismic p waves recorded by a dense broadband seismic array in taiwan with epicentral distances of close to 31 the azimuthal variation from the bats array center to both ends of the rupture fault is approximately 21 which is larger than that reported previously for seismic arrays used to image the rupture process of this earthquake thereby providing a high spatial resolution in studying the source rupture behavior two array processing methods were used to analyze teleseismic p wave trains both analyses were based on data recorded by a broadband network covering a region of 200 400 km with the aim of evaluating the rupture behavior of the earthquake consistent results from both analyses indicate that the earthquake had a rupture duration exceeding 500 s with major asperities encountered at 80 260 and 330 s after the initiation of rupturing we traced the ruptured fault for more than 1200 km from the point of initial rupture the average rupture velocity was approximately 3 0 km s and the major northward rupture propagation began at 80 s after the initiation of rupturing

eastern termination of the altyn tagh fault western china constraints from a magnetotelluric survey the left lateral altyn tagh fault forms the northern boundary of the tibetan plateau the strike slip rate of the active altyn tagh fault decreases northeastward and reduces close to zero as it passes north of the qilian shan this geometry raises controversies on whether and how the fault terminates or extends further east to address these controversies wide band magnetotelluric data were collected along four profiles across the altyn tagh fault ranging from 135 to 261 km in length all four profiles are located in the foreland of the qilian shan ranges and are oriented perpendicular to the inferred fault zone that could be the continuation of altyn tagh fault both the two dimensional and three dimensional electrical resistivity models derived from our magnetotelluric data show that the hexi corridor crust is generally of low resistivity whereas the crust of the huahai jinta basin is in general of high resistivity with a local and isolated low resistivity anomaly within the mid lower crust the generally high resistivity crust of the huahai jinta basin may be rheologically unfavorable for the altyn tagh fault passing through the basin toward the northeast the entirely different electrical structure between the hexi corridor and its northern neighbors indicates the existence of a tectonic boundary that coincides with the altyn tagh fault in the west and reverse faults in the east the two dimensional electrical conductivity models suggest that the altyn tagh fault transfers from a single fault in the west to a branching set of mainly dip slip faults in the east

cenozoic tectonic evolution of the new zealand plate boundary zone a paleomagnetic perspective abstract new zealand straddles the obliquely convergent boundary between the pacific and australian plates with subduction of pacific plate along the hikurangi margin finite plate reconstructions predict 800 km of relative plate motion since 43 ma with 80 90 clockwise rotation of the hikurangi margin since 20 ma at an average rate of 4 4 5 myr and the short term deformation

limestone and chert in tectonic blocks from the esk head subterrane south island new zealand the esk head subterrane is a continuous belt generally 10 20 km wide of tectonic melange and broken formation on the south island of new zealand this subterrane separates older and younger parts of the torlesse terrane which is an extensive accretionary prism composed mostly of quartzo feldspathic submarine fan deposits ranging from permian to early cretaceous in age the torlesse is the most pacific ward of several permian and mesozoic accreted terranes in new zealand that record tectonic amalgamation and ultimate accretion against the pacific facing gondwana margin the esk head subterrane of the torlesse is especially informative because it includes within it conspicuous tectonic blocks of submarine basalt and a variety of basalt associated seamount and sea floor limestones and cherty rocks thought to be representative of the subducted plate limestones in tectonic blocks are of late triassic and probably jurassic ages and include 1 submarine cemented pelagic bivalve geopetal packstone grainstone 2 brachiopod bryozoan encrinite and 3 radiolarian pelagic lime mudstone most of the triassic blocks have been dated using conodonts which have remarkably low color alteration index cai values paleogeographic inferences drawn from megafossils bioclasts and radiolarians as well as from carbonate cements indicate deposition of the oceanic sedimentary rocks at paleolatitudes somewhat lower than that of the new zealand part of the gondwana margin but higher than paleoequatorial latitudes these oceanic sediments and their basaltic substrates were evidently emplaced in the torlesse accretionary prism following off scraping from an extensive subducting oceanic plate probably the phoenix plate which was obliquely convergent with the northwest trending gondwana margin during late jurassic and or early cretaceous time

the mechanism of the deep bolivia earthquake of june 9 1994 we analyzed the iris broad band seismograms for the june 9 1994 bolivia earthquake the largest deep focus earthquake ever recorded we inverted the record sections with a duration of 330 sec which include p pp and sp phases and obtained a dip slip mechanism dip rake strike 13 4 1 or 89 103 95 with a scalar moment of mo 2 9 10 21 nm mw 8 2 this mechanism is similar to that obtained from long period 175 to 250 sec rayleigh and love waves 83 100 90 mo 3 0 10 21 nm mw 8 3 the main rupture was preceded by about 10 sec by a cluster of smaller events with a total moment of 1 2 10 20 nm mw 7 3 the main rupture starts at about 20 km east or northeast of the initial break and propagates horizontally in the east to northeast direction the source duration is 40 sec and the rupture dimension is about 40km if a fault area of 40 40km is assumed the stress drop is 110 mpa an inversion of body waves p pp and sp with 6 basis moment tensors yielded a best fit solution with a 10 implosive component this result is of marginal significance and its confirmation would require more detailed information on the structures near the source region pp bounce points and stations the observed amplitude of the radial mode 0s 0 1226 sec is consistent with a double couple model with less than 2 isotropic component

en echelon ruptures during the great bolivian earthquake of 1994 rupture during this event has two characteristics first bursts of major moment release subevents have a component of eastward movement from the epicenter second later subevents show northward directivity these observations lead to a model with four subevents the latter three being line sources propagating within approximately 30 of north this model has en echelon regions of moment release over sub horizontal plane s and rupture speeds up to 3 5 0 5 km s within subevents moment release over en echelon regions can accommodate high moment release over a limited seismogenic volume within subducted lithosphere depending on the exact geometry of the wadati benioff zone and the precise direction of rupture propagation lower bounds on the thickness of the seismogenic zone during this event range approximately 10 40 km while several aspects of the en echelon rupture model dovetail with predictions based on the anticrack model for deep focus seismicity one must also allow for the possibility that the rupture zone extended beyond the expected thickness of metastable olivine wedge

do intermediate and deep focus earthquakes occur on preexisting weak zones an examination of the tonga subduction zone it has been proposed that intermediate and deep focus earthquakes occur on preexisting planes of weakness that were created at shallow depth the purpose of this study is to test this hypothesis we examined fault plane solutions for 360 events that occurred in the tonga subduction zone from january 1976 to february 1999 for events in the slab each fault plane solution is rotated by the slab dip angle so that the slab is in its original horizontal position we then compare fault plane solutions for events in the slab with those for events at the outer rise we find that an asymmetric fault system corresponding to that found for outer rise events persists down to about 450 km depth this suggests that earthquakes down to this depth are caused by the reactivation of preexisting faults created in the oceanic plate before subduction a similar pattern though less well constrained is found in the kurile subduction zone down to 200 km depth for earthquakes deeper than 450 km the fault plane solutions are much more scattered in some places the fault plane pattern suggests the creation of new fault planes along orientations of maximum shear with zero internal friction the pattern of fault plane solutions in particular localized volumes cannot be easily explained by the creation of new faults in the direction of maximum shear under a coherent regional tectonic stress field thus either a highly heterogeneous stress field exists or preexisting planes of weakness also account for some deep earthquakes

significant contribution of the shallow crust to seismic pkp travel time residuals and implications an example from taiwan and nearby islands abstract array observations indicate that the relative pkp travel time residuals in the taiwan region vary from 2 5 to 2 0 s a range greater than the largest known teleseismic travel time residuals from deep earth pkp waves are generally employed to probe structures of the deep earth however the contribution of shallow geological structures to pkp waves is generally undefined and the implications of such a contribution have rarely been discussed current travel time tomographic models of taiwan are able to predict less than 40 of the observed pkp residuals and the pkp residuals are consistent with the pattern of station corrections used in determining local earthquakes detailed island wide gravity measurements indicate that the distribution of bouguer anomalies which were previously proposed to be induced by thick sedimentary deposits in large tectonic basins is consistent with the pattern of pkp travel time residuals in conclusion the observed pkp residuals are strongly affected by shallow sediments therefore the contribution of residuals from shallow crustal structures should be carefully considered when employing pkp observations for imaging structures of the deep earth or the deep crust and upper mantle

localized versus distributed shear in transform plate boundary zones the case of the dead sea transform in the jericho valley 1 continental transform plate boundaries are typically either localized along a single usually segmented major fault or distributed over a broad deformation zone in the latter shear is partitioned between major strike slip faults and intervening often rotating fault systems analog and numerical simulations suggest that such internal fault systems evolve and may be localized or delocalized depending on strain and fault zone strength this paper examines the degree and evolution of shear localization in the jericho valley section of the dead sea transform dst which is part of the africa arabia plate boundary in this section the current breadth of the transform valley and its penetrative strain field are difficult to reconcile with localized shear we integrate newly acquired high resolution reflection data reprocessed exploration reflection data both focused to 2 5 3 5 km depth relatively relocated earthquake epicenters and fault plane solutions based on p wave first arrivals and suggest reinterpretations for previously published structural and seismic data in the jericho valley and the northern dead sea basin it is found that shear in this section of the dst evolved from an early probably miocene pliocene stage of localized strike slip motion primarily along the jericho fault to a late stage pliocene recent when shear has been distributed over internal fault sets that apparently lean against a major eastern dst segment in the early stage the jericho fault formed the western boundary of a deep narrow probably pull apart basin filled by fluvial clastics and evaporites this is overlain by the late stage broad basin characterized by low energy deposition of lacustrine and fluvial sediments pliocene rock salt has apparently utilized the jericho fault zone as a conduit for diapirism causing the uplift normal faulting and surface deformation of late pleistocene and holocene sediments currently observed along the 15 km long jericho lineament on the basis of the currently observed dextral normal motion across the internal nne ne trending fault system counterclockwise rotation is expected to have occurred within the transform zone these tectonic and depositional changes were probably associated with onset of transtension across the dst related to the previously postulated shift of the africa arabia euler pole of rotation in the pliocene

depositional and summer snow melting features in 2007 2011 on the upstream side of potanin glacier mongolian altai reconstructed by pollen and oxygen isotope analysis this study analyzed pollen in snow pits dug in late summer 2008 2011 on the upstream side of potanin glacier a summer accumulation type glacier in the mongolian altai to reconstruct the recent snow depositional environment particularly melting conditions annual snow pit observations were performed at sites 0 and 4 3752 and 3890 m a s l respectively seasonal layers in the pits were identified according to the presence of pollen from three taxa betulaceae pinus and artemisia which have different pollen seasons typically between may and early september the pollen dating method was successful in snow pits where conventional methods such as ice layer dating and use of 18o records were unreliable due to significant melting depths of pollen concentration peaks for the three taxa differed annually at both sites in some years concentration peaks of the three pollen taxa were found at different depths but in other years peaks associated with each taxon were found at the same depth this difference was explained by summer temperature snow melting during the relatively warm summers of 2007 and 2008 caused pollen grains to concentrate on the glacier surface producing peaks at the same depth in contrast snow melting during the relatively cool summer of 2009 did not substantially alter pollen grain location and each peak thus retained its original depth the median temperatures in 2010 and 2011 corresponded to pollen concentrating on the glacier surface at site 0 but retaining their original position at site 4

hope fault jordan thrust and uplift of the seaward kaikoura range new zealand in the northern south island of new zealand displacement at the pacific indian plate boundary is accommodated by the east north east striking right lateral strike slip marlborough fault system the southernmost marlborough fault is the hope fault the late pleistocene holocene horizontal slip rate on this fault is 20 25 mm yr about half of the rate of pacific australian plate motion near the eastern end of the hope fault most displacement is transferred to the north northeast striking jordan thrust but the average dip slip rate at the surface trace of this thrust is less than 4 mm yr we propose that most slip takes place on a blind thrust expressed at the surface by the fault propagation folding of the seaward kaikoura range and that the rate of uplift of this range is as high as that of the southern alps 6 to 10 mm yr the major restraining bend of the alpine fault has the same average slip rate as the wairau fault 4 6 mm yr even though the alpine fault is an east dipping reverse separation fault at the restraining bend this low slip rate results in uplift of the spenser mountains east of the bend at a rate lower than that of the southern alps and seaward kaikoura range

reconstruction of the late glacial and holocene history of lake oron eastern siberia russia based on high resolution reflection seismic data high resolution seismic data have been used to study the sedimentary infill of lake oron we have tested the idea that glacial lake vitim could be formed when glaciers descending from the kodar mountains blocked the vitim river at lake oron the five seismic facies types shallow pelagic mudslide and turbidite rock sandslide and alluvial or glacial fan facies and five seismic units were identified in the sedimentary infill of lake oron however features that could represent moraines were not observed on the seismic profiles and along the shoreline of lake oron it is very likely that terminal moraines did not dam the vitim river up to 840 60 m a s l at the end of the last glacial maximum lgm we assume that the oron depression was mainly dry and glaciers lobes could be located close to the eastern edge of lake oron in valleys of the sygykta kultushnaya and kamennaya rivers during the lgm intensive inflow of meltwater and river input into lake oron began since ca 18 ka bp after ca 5 ka bp the supply of surface water into the lake sharply reduced

seismicity and fault kinematics through the eastern transverse ranges california block rotation strike slip faulting and low angle thrusts hypocentral locations and first motion data from the southern california seismic network are used to infer the present pattern of deformation along the southern san andreas fault the study area lies between the san jacinto fault and desert hot springs and includes the san bernardino mountains and san gorgonio pass this region has some of the deepest earthquakes observed anywhere along the entire san andreas system exhibits a complex surface geology characterized by both right and left lateral faults has high topographic relief as a result of recent uplift and is a potential site for the nucleation of a great earthquake although this area is unusually seismogenic little activity can be directly associated with major throughgoing faults seismicity is also generally absent in the upper 5 km the predominant style of faulting above 10 12 km is oblique slip with a large reverse component the spatial distribution of relocated hypocenters and first motion data suggests the presence of a system of left slip faults striking northeast this pattern of faulting in conjunction with an unusual set of normal and reverse focal mechanisms is interpreted as the clockwise rotation of a small set of crustal blocks subject to regional right lateral shear at depths greater than about 10 km seismicity defines a wedge shaped volume undergoing pervasive internal deformation on a combination of strike slip and low angle thrust faults velocity structures determined from earthquake arrival times suggest a low velocity zone at about 10 km below the san bernardino mountains but not below the san jacinto mountains this is nearly the same depth as the transition between the two layers of different kinematic behavior seen south of the mill creek mission creek branch of the san andreas fault and the maximum depth of seismicity seen north of that fault the low velocity zone and the transition between block rotations and the deeper deformation may thus correspond to a detachment under much of this region and would imply that the overthrust san bernardino mountains are allochthonous the present pattern of seismic deformation in shocks of small to moderate size may only characterize the interval between large earthquakes and may change systematically as the region prepares to accommodate large right lateral displacements

the last 25 ma of rotational deformation in part of the new zealand plate boundary zone abstract the marlborough fault system is a zone of dextral transpression in continental crust and marks the southern end of the hikurangi subduction system between the obliquely convergent australian and pacific plates detailed mapping over an area of 100 km2 has revealed a complex history of deformation during the last 25 ma the development of a thrust belt in the miocene referred to as d1 deformation was synchronous with the deposition of a thick submarine fan complex the beginning of d1 deformation may mark the initiation of the subduction zone in this part of the plate boundary zone subsequently in the plio pleistocene the region formed a zone of dextral shear marked by major strike slip faults and zones of distributed deformation referred to as d2 deformation crustal blocks less than 5 km across may have rotated ca 60 clockwise about vertical axes relative to the pacific plate in the last 4 ma the pattern of deformation during the last 10 ka to 100 years is consistent with the long term d2 deformation and suggests that large crustal blocks resting on the subducted pacific plate have rotated clockwise about vertical axes relative to the pacific plate accommodated by dextral shear further to the sw in the marlborough fault system the overall effect of the deformation has been the rotation of the edge of the southern part of the hikurangi margin from a w to nw trend in the early miocene to a ne trend today

the temporal distribution of seismic radiation during deep earthquake rupture the time history of energy release during earthquakes illuminates the process of failure which remains enigmatic for events deeper than about 100 kilometers stacks of teleseismic records from regional arrays for 122 intermediate depths of 100 to 350 kilometers and deep depths of 350 to 700 kilometers earthquakes show that the temporal pattern of short period seismic radiation has a systematic variation with depth on average for intermediate depth events more radiation is released toward the beginning of the rupture than near the end whereas for deep events radiation is released symmetrically over the duration of the event with an abrupt beginning and end of rupture these findings suggest a variation in the style of rupture related to decreasing fault heterogeneity with depth