mineral magnetic record of late quaternary climatic changes in a high alpine lake the magnetic properties of a sediment core from a high altitude lake in the swiss alps were compared with palynological and geochemical data to link climatic and mineral magnetic variations according to pollen data the sediments extend from the present to the younger dryas i e they cover more than 10 000 years of environmental change in the alps the major change in magnetic properties corresponds to the climatic warming of the early holocene high coercivity magnetic minerals that characterize the late glacial period almost disappeared during the holocene and the concentration of ferrimagnetic minerals increased sharply the contribution of superparamagnetic grains also decreased in the holocene sediments similar variations in sp content and coercivity of smaller magnitude are found in the holocene and are interpreted to represent minor climatic variations comparison with the historical record of the last 1000 years confirms this interpretation the magnetic mineralogy the superparamagnetic contents and the irm intensity in the coarse grained late glacial sediments are similar to those measured in the catchment bedrock this indicates a detrital origin the different properties and the higher concentration of magnetic minerals in the holocene sediments are due to authigenic phases magnetic properties provide a high resolution record of climatic change they are sensitive even to small variations that are not recorded in the pollen or loi data magnetic parameters show fine scale variation and constitute a valuable supplement to conventional climatic indicators 1999 elsevier science b v all rights reserved

the detection of low magnitude seismic events using array based waveform correlation summary it has long been accepted that occurrences of a known signal are most effectively detected by cross correlating the incoming data stream with a waveform template such matched signal detectors have received very little attention in the field of detection seismology because there are relatively few instances in which the form of an anticipated seismic signal is known a priori repeating events in highly confined geographical regions have been observed to produce very similar waveforms and good signals from events at a given site can be exploited to detect subsequent co located events at lower magnitudes than would be possible using traditional power detectors even greater improvement in signal detectability can be achieved using seismic arrays running correlation coefficients from single sensors can be stacked over an array or network to result in a network correlation coefficient displaying a significant array gain if two events are co located the time separating the corresponding patterns in the wave train as indicated by the cross correlation function is identical for all seismic stations and this property means that the correlation coefficient traces are coherent even when the waveforms are not we illustrate the power of array based waveform correlation using the 1997 august 16 kara sea event the weak event that occurred 4 hr after the main event was barely detected using an sta lta detector on the spits array but is readily detected by signal matching on a single channel the main event was also recorded by the far more distant norsar array but no conventional detection can be made for the second event a clear detection is however made when the correlation coefficient traces are beamformed over all sensors of the array we estimate the reduction in detection threshold of a test signal on a regional seismic array using waveform correlation by scaling down a master signal and immersing it into seismic noise we show that for this case waveform correlation using a single channel detects signals of approximately 0 7 orders of magnitude lower than is possible using an sta lta detector on the array beam waveform matching on the full array provides an additional improvement of approximately 0 4 magnitude units we describe a case study in which small seismic events at the barentsburg coal mine on spitsbergen were detected using the signals from a major rockburst as master waveforms many spurious triggers occurred in this study whereby short sections of signal exhibited coincidental similarity with unrelated incoming wave fronts we demonstrate how such false alarms can almost always be identified and screened out automatically by performing frequency wavenumber analysis upon the set of individual correlation coefficient traces

a major change in precipitation gradient on the chinese loess plateau at the pliocene quaternary boundary abstract spatiotemporal variations in east asian monsoon eam precipitation during the quaternary have been intensively studied however spatial variations in pre quaternary eam precipitation remain largely uninvestigated preventing a clear understanding of monsoon dynamics during a warmer climatic period here we compare the spatial differences in heavy mineral assemblages between quaternary loess and pre quaternary red clay on the chinese loess plateau clp to analyze spatial patterns in weathering prior studies have revealed that unstable hornblende is the dominant 50 heavy mineral in chinese loess deposited over the past 500 ka whereas hornblende content decreases to

improving local earthquake locations using the l1 norm and waveform cross correlation application to the whittier narrows california aftershock sequence experiments with different earthquake location methods applied to aftershocks of the october 1 1987 whittier narrows earthquake in california ml 5 9 suggest that local event locations can be greatly improved through the use of the l1 norm station corrections and waveform cross correlation the whittier narrows sequence is a compact cluster of over 500 events at 12 to 18 km depth located within the dense station coverage of the southern california seismic network scsn a telemetered network of several hundred short period seismographs scsn travel time picks and waveforms obtained through the southern california earthquake center are examined for 589 earthquakes between 1981 and 1994 in the vicinity of the mainshock using a smoothed version of the standard southern california velocity model and the existing travel time picks improved location accuracy is obtained through use of the l1 norm rather than the conventional least squares l2 norm approach presumably due to the more robust response of the former to outliers in the data a large additional improvement results from the use of station terms to account for three dimensional velocity structure outside of the event cluster to achieve greater location accuracy waveforms for these events are resampled and low pass filtered and the p and s wave cross correlation functions are computed at each station for every event pair for those events with similar waveforms differential times may be obtained from the cross correlation functions these times are then combined with the travel time picks to invert for an adjusted set of picks that are more consistent than the original picks and include seismograms that were originally unpicked locations obtained from the adjusted picks show a further improvement in accuracy location uncertainties are estimated using a bootstrap technique in which events are relocated many times for sets of picks in which the travel time residuals at the best fitting location are used to randomly perturb each pick improvements in location accuracy are indicated by the reduced scatter in the residuals smaller estimated location errors and the increased tendency of the locations to cluster along well defined fault planes median standard errors for the final inversion are 150 m in horizontal location and 230 m in vertical location although the relative locations within localized clusters of similar events are better constrained seismicity cross sections resolve the shallow dipping fault plane associated with the mainshock and a steeply dipping fault plane associated with a ml 5 3 aftershock these fault planes appear to cross and activity began on the secondary fault plane prior to the large aftershock

the rise collapse and compaction of mt mantap from the 3 september 2017 north korean nuclear test surveillance of clandestine nuclear tests relies on a global seismic network but the potential of spaceborne monitoring has been underexploited we used satellite radar imagery to determine the complete surface displacement field of up to 3 5 meters of divergent horizontal motion with 0 5 meters of subsidence associated with north korea s largest underground nuclear test combining insight from geodetic and seismological remote sensing we found that the aftermath of the initial explosive deformation involved subsidence associated with subsurface collapse and aseismic compaction of the damaged rocks of the test site the explosive yield from the nuclear detonation with best fitting source parameters for 450 meter depth was 191 kilotonnes of tnt equivalent our results demonstrate the capability of spaceborne remote sensing to help characterize large underground nuclear tests

the 9 september 2016 north korean underground nuclear test we characterize the seismic events that occurred in north korea on 9 september 2016 and south korea on 12 september 2016 the 9 september 2016 event was identified as an explosion and the two 12 september 2016 events were identified as natural earthquakes using the p s p and s wave spectral ratios pg lg pn lg and pn sn as discriminants the explosive event was relocated within the north korean nuclear test site using a relative location method and the 2006 north korea underground nuclear test as the master event and the epicenter was identified at 41 2976 degrees n latitude and 129 0804 degrees e longitude from the regional lg and rayleigh waves the body and surface wave magnitudes for the 9 september 2016 event were calculated as m b lg 4 8 0 2 and m s 4 2 0 1 by adopting an empirical magnitude yield relation for the body wave magnitude and assuming that the explosion was fully coupled and detonated at a normally scaled depth we estimated that the seismic yield was similar to 6 kt and the uncertainty range was between 3 and 11 kt if an overburied depth range between 780 and 1200 m was applied then the yield would be increased to 16 22 kt

high precision location and yield of north korea s 2013 nuclear test 1 using north korea s 2009 nuclear test as reference and satellite imagery we show that the location and yield of north korea s 2013 nuclear test can be quickly and accurately determined based on seismic data north korea s 2013 nuclear test site is pinpointed by deriving relative location of north korea s 2009 and 2013 nuclear tests and using the previously determined location of the 2009 nuclear test while its yield is estimated based on the relative amplitude ratios of the lg waves recorded for both events the previously determined lg magnitude of 2009 nuclear test and burial depth inferred from satellite imagery north korea s 2013 test site is determined to be located at 41 17 26 88 n 129 4 34 68 e about 345 m south and 453 m west of its 2009 nuclear test site with a geographic precision of 94 m its yield is estimated to be 12 2 3 8 kt

southern hemisphere forcing of pliocene δ18o and the evolution of indo asian monsoons monsoon phase relationships consistent with direct orbital forcing across the entire indo asian region including marine and terrestrial proxies from the chinese loess plateau the south china sea and the arabian sea strong pliocene summer and winter monsoons were in phase with one another strengthened at obliquity minima and precession minima the summer monsoon was also strengthened at precession maxima yielding a semiprecession spectral signal strong pliocene monsoons at orbital extremes indicate a direct response to fast physics processes including sensible heating and cooling of the asian landmass and for the summer monsoon the export of latent heat from the southern indian ocean as northern hemisphere ice volume grew into the pleistocene the timing of strong winter and summer monsoons drifted apart becoming influenced by the combined effects of fast physics and slow physics ice volume variables the phase of strong winter monsoons shifted toward ice maxima and the phase of strong summer monsoons shifted toward ice minima

el nino s tropical climate and teleconnections as a blueprint for pre ice age climates 1 at 2 7 million years ago the warm equable climates of early and middle pliocene time used here to mean from 5 to 2 7 ma were replaced by recurring ice ages most attempts to explain the change appeal either to changes in co2 in the atmosphere or reduced heat transport by the atlantic ocean the sources of the strongest teleconnections in the current climate however lie in the tropics and such connections occur by transport of heat and moisture by the atmosphere the most prominent of these teleconnections link aberrations in sea surface temperatures in the equatorial pacific el nino southern oscillation enso variations with warm and dry or cool and wet anomalies in extratropical climates we show that in most cases early and middle pliocene climate both in equatorial regions and in the extratropics differ from present day climates with the same spatial pattern as that associated with enso for instance not only was canada warmer during early pliocene time than at present as it is during el nino but the region surrounding the gulf of mexico appears to have been cooler and a bit wetter as it commonly is during el nino a virtually permanent el nino like state appears to have characterized pre ice age climates suggesting that transport of heat by the atmosphere was the principal mechanism that maintained extratropical warmth accordingly cooling and the growth of recurring ice sheets in the northern hemisphere resulted from the development of a strong walker circulation and a weakening of the hadley circulation

improvements to seismic monitoring of the european arctic using three component array processing at spits abstract the detectability of low magnitude seismic events in the european arctic is determined primarily by the small aperture international monitoring system arrays arces and spits in august 2004 the spits array was upgraded to a broadband array with an increase in the sampling rate from 40 to 80 hz most important however for the detection and location of small magnitude seismic events was the deployment of three component instruments at six of the nine sites detection and correct classification of secondary phases are of paramount importance for events observed by only a small number of stations at regional distances and in the absence of the strong lg phases typically observed for continental propagation paths multiple three component stations were deemed necessary to exploit the higher s phase amplitudes anticipated on the horizontal sensors we demonstrate improved signal to noise ratios snrs for s phases on horizontal beams for several events close to novaya zemlya horizontal component f k analysis improves direction estimates and phase classification for low snr signals we demonstrate secondary phases that are misidentified by vertical only f k analysis but which are correctly classified by three component array processing a significant problem with array processing at spits is the overlap in slowness space of regional p and s phases phase identification is improved greatly by comparing the coherence between vertical traces with the coherence between horizontal traces considerations in the routine array processing of spits data are reviewed including the need for elevation corrections in slowness estimation and the need to take into account azimuth dependent variation of apparent velocity estimates for regional phases

lateglacial and early holocene summer temperatures in the southern swiss alps reconstructed using fossil chironomids we present a lateglacial and early holocene chironomid based july air temperature reconstruction from foppe 1470 m a s l in the swiss southern alps our analysis suggests that chironomid assemblages have responded to major and minor climatic fluctuations during the past 17 000 years such as the oldest dryas the younger dryas and the bolling allerod events in the lateglacial and the preboreal oscillation at the beginning of the holocene quantitative july air temperature estimates were produced by applying a combined norwegian and swiss temperature inference model consisting of 274 lakes to the fossil chironomid assemblages the foppe record infers average july air temperatures of ca 9 9 8c during the oldest dryas 12 2 8c during most of the bolling allerod and 11 1 8c for the younger dryas mean july air temperatures during the preboreal were 14 8c major temperature changes were observed at the oldest dryas bolling 2 7 8c the allerod younger dryas 2 8c and the younger dryas holocene transitions 3 9 8c the temperature reconstruction also shows centennial scale coolings of ca 0 8 1 4 8c which may be synchronous with the aegelsee greenland interstadial 1d and the preboreal oscillations a comparison of our results with other palaeoclimate records suggests noticeable temperature gradients across the alps during the lateglacial and early holocene copyright 2011 john wiley sons ltd

100 year mass changes in the swiss alps linked to the atlantic multidecadal oscillation thirty new 100 year records of glacier surface mass balance accumulation and melt in the swiss alps are presented the time series are based on a comprehensive set of field data and distributed modeling and provide insights into the glacier climate linkage considerable mass loss over the 20th century is evident for all glaciers but rates differ strongly glacier mass loss shows multidecadal variations and was particularly rapid in the 1940s and since the 1980s mass balance is significantly anticorrelated to the atlantic multidecadal oscillation amo index assumed to be linked to thermohaline ocean circulation we show that north atlantic variability had a recognizable impact on glacier changes in the swiss alps for at least 250 years citation huss m r hock a bauder and m funk 2010 100 year mass changes in the swiss alps linked to the atlantic multidecadal oscillation geophys res lett 37 l10501 doi

quantitative assessment to the impact of insar ionospheric and tropospheric corrections on source parameter modelling application to the 4th nuclear test north korea

advanced seismic analyses of the source characteristics of the 2006 and 2009 north korean nuclear tests in 2006 and 2009 north korea conducted underground nuclear tests at a remote mountainous site in the northeastern part of the country both events were small leading to uncertainties for location yield estimation and discrimination based on seismic observations the objectives of the studies described in this paper have been to more fully exploit data from the international monitoring system ims network and other unclassified sources e g incorporated research institutions for seismology iris japanese national research institute for earth science and disaster prevention nied to analyze these nuclear tests we have used differential waveform interferometry dwif to refine relative locations for the tests and extended the methodology using observations from regional stations to estimate relative emplacement depths which are consistent with explosion source model predictions for broadband regional p wave spectral ratios topographic data from the test site were analyzed to constrain relative locations and depths needed for containment of the two tests based on normal testing practice network averaged teleseismic p wave spectra were inverted using a model based approach and provide explosion yield estimates in the range 0 6 1 0 kt for the 2006 test and 2 0 4 8 kt for the 2009 test depending on assumed emplacement depth detailed spectral analysis of broadband regional p observations are most consistent with theoretical explosion models with yields of 0 9 and 4 6 kt for the 2006 and 2009 tests respectively with associated source depths of 200 and 550 m consistent with previous studies the surface wave m s magnitudes for the 2006 and 2009 tests provide anomalously large m s yield estimates and problematic m s m b identification characteristics finite difference simulations of long period surface wave signals incorporating tensile prestress consistent with the regional tectonics lead to predicted m s values that agree much better with the observed values

a tree ring based reconstruction of the atlantic multidecadal oscillation since 1567 a d 1 we present a tree ring based reconstruction of the atlantic multidecadal oscillation amo which demonstrates that strong low frequency 60 100 yr variability in basin wide 0 70 n sea surface temperatures ssts has been a consistent feature of north atlantic climate for the past five centuries intervention analysis of reconstructed amo indicates that 20th century modes were similar to those in the preceding 350 yr and wavelet spectra show robust multidecadal oscillations throughout the reconstruction though the exact relationships between low frequency sst modes higher frequency 7 25 yr atmospheric modes e g north atlantic oscillation arctic oscillation and terrestrial climates must still be resolved our results confirm that the amo should be considered in assessments of past and future northern hemisphere climates

relative locations of the october 2006 and may 2009 dprk announced nuclear tests using international monitoring system seismometer arrays abstract waveform data recorded at seven of the international monitoring system ims seismometer arrays are used to measure the relative times of teleseismic p signals with three methods analyst picks and two methods that make full use of the capabilities of seismometer arrays the cross correlation of array beams and the average of channel by channel cross correlations these times are used to estimate the relative locations of the 9 october 2006 and 25 may 2009 democratic people s republic of korea announced underground nuclear tests the 2009 test is found to have occurred about 1 8 0 8 km to the west and 0 4 0 6 km to the north of the 2006 test the use of cross correlation reduces the standard deviation of the travel time residuals from 0 05 to 0 01 sec enabling the two epicenters to be statistically distinguished with high confidence this result demonstrates the power of a small number of ims seismometer arrays at teleseismic distances to detect and relatively locate small explosions with high precision

preliminary results from laguna minucua a potentially annually resolved record of climate and environmental change for the past 5000 years in the mixteca alta of oaxaca mexico abstract despite several decades of research focusing on prehispanic human ecology debate continues over the impact of climatic and anthropogenic landscape change on human populations in mesoamerica one problem in identifying the cause of this change is the lack of high resolution paleo environmental data from many regions the southern mexican highlands in particular have yielded few paleoenvironment data yet have a rich and diverse cultural history the sedimentary record from laguna minucua located within the sierra madre del sur oaxaca offers an exceptional opportunity to address human and environmental interactions in the region minucua is a small 0 25 ha currently shallow pond with no apparent inlets or outlets we retrieved two sediment cores from the site 3 5 m and 5 6 m long the cores are highly laminated core chronology was developed with paleomagnetic secular variation data and compared with couplet counts and limited radiometric measurements these data indicate that the minucua record at least spans the last 4500 100 years we discuss preliminary results that assess long term environmental change for the region through examination of geochemical and magnetic susceptibility data in particular we discuss in more detail a 500 year time slice which encompasses the period known as the classic collapse the record indicates overall dry conditions but with two extended wet periods experienced between 1160 and 1120 cal yr bp and 1060 1000 cal yr bp we place our findings in the context of current archaeological and paleoclimatological research in oaxaca

tracking the north korean nuclear explosion of 2006 using seismic data from japan and satellite data from taiwan abstract the location of the 2006 nuclear explosion in north korea has been accurately imaged by back projected regional pn waves recorded by the japanese hi net array based on the determined location the nuclear explosion site can be identified from geo referenced formosat 2 satellite images the seismically determined epicenter is about 2 5 km northeast of the original estimate of its absolute location results indicate that a remote suspect event had been unambiguously detected and accurately located by a dense array within a regional distance employing ground truth correction the satellite images can be referenced for shifting the array determined epicenter to its absolute position after correction this event can be treated as a reference event for accurately locating future nuclear explosions our study utilizes public information from a dense seismic network and further demonstrates that commercial observation satellites can accurately monitor compliance with the comprehensive nuclear test ban treaty as well as earthquake and tsunami hazards almost in real time

relative surface wave amplitude and phase anomalies from the democratic people s republic of korea announced nuclear tests relative amplitude and phase anomalies we performed relative locations of six event pairs based on surface wave sw and body wave bw differential travel times of the 2016 09 09 2016 01 06 2013 02 12 and 2009 05 25 announced north korea nuclear explosions the sw relative locations for the 2009 05 25 and 2013 02 12 events were inconsistent with the bws when paired with other events and only the 2016 01 06 2016 09 09 pair was consistent apparent sw phase shift is investigated with respect to the bw relative locations the pairs formed with the 2009 05 25 and 2013 02 12 events beneath the southeast slope of mount mant ap have the largest phase shifts and amplitude ratio deviations whereas the least deviation was from the 2016 01 06 and 2016 09 09 event pair beneath the mountain peak regional moment tensors mts predict the amplitude ratios but do not resolve the relative phase we find mts with 10 difference in isotropic and rotated clvd can fit both relative phase and amplitude ratios sw relative locations of highly isotropic and correlated explosion clusters can be affected by topography and small differences in mt

a record of holocene climate in the mineral magnetic record of alpine lakes sagistalsee and hinterburgsee the effect of climate variations on the magnetic properties of sediments from two small alpine lakes in the bernese alps switzerland was investigated although relatively similar in water volume and general environment sa gistalsee and hinterburgsee have different catchment vegetation and lithology due to their different elevation and geographic locations the climatic signal in the mineral magnetic parameters of the sediments was validated and interpreted with the aid of palynological and geochemical data the sediment age was determined with several accelerated mass spectrometry 14 c dates the results from the different lakes compare well on a common time scale and show that the influence of local conditions on the magnetic record is rather small a climatic influence on the mineral magnetism has been recognized at both studied sites this is interpreted as a consequence of the production of an authigenic mineral with particularly uniform magnetic properties during the warmer stages and the influx of heterogeneous detrital magnetic minerals during the colder stages the clearest climate record is found in sediments with no organic matter whereas the anoxic conditions found in highly organic sediment can completely obliterate the climate signal recorded in the sediment magnetic properties fl 2001 elsevier science b v all rights reserved

accurate locations of nuclear explosions at the lop nor test site using alignment of seismograms and ikonos satellite imagery locations are estimated of 11 underground nuclear explosions conducted between 26 may 1990 and 29 july 1996 at the lop nor test site in western china to perform the analysis seismic recordings were obtained from the center for monitoring research cmr u s national data center and incorporated research institutions for seismology iris data management center using recordings with adequate signal to noise ratios p wave arrivals are picked manually by aligning waveforms of the events at common stations this provides very precise relative phase timings i e with relative errors typically much less than 0 1 sec based on analysis of commercial ikonos satellite imagery the locations of three explosions are fixed and used as master events the other events are located relative to the nearest master event after correcting their travel times by the travel time residuals relative to iasp91 of the master events location estimates of the 25 september 1992 and 29 july 1996 nuclear tests are within about 100 m of each other the 90 confidence error ellipse for the 29 july 1996 event has a semimajor axis of less than 0 3 km the results indicate that these two tests were likely conducted in the same tunnel location estimates of nine explosions conducted at the eastern zone of the lop nor test site are within 140 to 490 meters of vertical boreholes and infrastructure to support nuclear testing observed in ikonos imagery the location estimates of the eleven chinese explosions are all considered to be well within one km of the true detonation points and hence are categorized as gt1 events as defined by yang et al 2000a these solutions allow seismic travel times to be calibrated accurately for the lop nor region at seismographic stations of the international monitoring system ims manuscript received 23 october 2001

evidence of atlantic multidecadal oscillation in the magnetic properties of alpine lakes during the last 2500 years abstract we re analyzed rock magnetic data of lake sediments from the alpine region which were previously recognized as sensitive climate proxy records in search of decadal climate variability different methods of spectral analysis applied to the rock magnetic data from two independent lake records show the presence of a coherent and statistically significant periodicity with a period of about 50 60 years the frequency filtered signal of this component co varies with the instrumental record of the atlantic multidecadal oscillation amo over the last 110 years with a negligible phase shift after having tested and ruled out the possible influence of solar irradiance in the putative amo frequency band based on spectral properties we suggest that a significant influence of amo in the alpine region extends back in time for at least two millennia comparison of the amplitude of the amo record with that of the younger dryas holocene transition suggests that amo fluctuations played a significant role in pacing the past variability of the alpine climate