fractal nature and scaling of normal faults in the espanola basin rio grande rift new mexico implications for fault growth and brittle strain abstract quaternary faults in the western espanola basin of the rio grande rift show a power law size displacement distribution suggesting that faulting in this region is scale invariant and that faults are self similar the power law or fractal distribution is characterized by fractal dimension of 0 66 to 0 79 and represents a young immature active fault population in a continental extensional regime based on this distribution it is estimated that unobserved faults with very small displacements account for up to 6 of the total strain since 1 2 ma total extension in this part of the basin has been at least 5 a direct correlation exists between maximum displacement and length of faults in this area suggesting that they obey a scaling relationship in which the ratio of log d max log l is 5 10 3 this ratio is nearly constant for faults whose lengths span three orders of magnitude indicating that there is no difference in the scaling relationship of displacement and length between faults of all sizes considering previous models these fault characteristics suggest that in the western espanola basin 1 host rock shear strengths are low 2 remote shear stresses were probably high and 3 most faults do not extend throughout the brittle crust finally displacement profiles on five of the largest faults arc asymmetric and show a rapid decrease in displacement from the point of maximum displacement toward the fault tip the fractal nature scaling relationship and distribution of displacement on faults are used to suggest that faults grew by nearly proportional increases in displacement and length perhaps by mechanisms dominated by propagating shear fractures rather than by linkage of pre existing joints or faults

climate and collapse agro ecological perspectives on the decline of the tiwanaku state abstract after approximately 700 years of growth and colonial expansion the tiwanaku state disintegrated as a regional political force in the south central andes between c ad 1000 1100 this paper examines the collapse of the state of tiwanaku through the lens of its agricultural history we argue that the proximate cause of tiwanaku s decline as a politically integrated expansive state society was the deterioration and ultimate abandonment of its regional scale agricultural systems both in its core area in the andean altiplano and in its economic colonies in the lower altitude yungas zones we present evidence that the collapse of tiwanaku intensive agriculture was triggered by regional change in climatic conditions recorded in highly resolved palaeoenvironmental data derived from the quelccaya ice cap of southern peru and in sediment cores from lake titicaca our analysis of the quelccaya data documents a radical climate change in the south central andes during the post ad 1000 era in the form of a statistically significant decrease in mean precipitation level that persisted until c ad 1400 by defining vulnerability classes for various agricultural technologies used in different regions of the tiwanaku state we then relate this palaeoclimatic data to performance of specific core area and colonial tiwanaku agricultural systems we demonstrate that chronic drought conditions led to sequential collapse of these distinct agricultural systems irrigation based agriculture in tiwanaku colonies at lower altitude failed first followed by groundwater dependent raised field systems in the altiplano agricultural and settlement pattern changes in the post ad 1000 period are correlated with the palaeoenvironmental data to present an integrated view of the coupling of climate and cultural process the full implications of the agro ecological collapse model presented here reach well beyond an explanation for the decline of tiwanaku alone

a fractal model for crustal deformation abstract we hypothesize that crustal deformation occurs on a scale invariant matrix of faults for simplicity we consider a two dimensional pattern of hexagons on which strike slip faulting occurs the behavior of the system is controlled by a single parameter the fractal dimension deformation occurs on all scales of faults the fractal dimension determines the fraction of the total displacement that occurs on the first order or primary faults the value of the fractal dimension can be obtained from the frequency magnitude relation for earthquakes our results are applied to the san andreas fault system in central california earthquake studies give d 1 90 we associate the main strand of the san andreas fault with the primary faults of our fractal system we predict that the relative velocity across the main strand is 2 93 cm yr the remainder of the relative velocity of 5 5 cm yr between the pacific and north american plates occurs on higher order faults the predicted value is in reasonably good agreement with the value 3 39 0 29 cm yr obtained from geological studies

the importance of small scale faulting in regional extension a recurring observation in many studies of extensional basins has been that the amount of extension visible on normal faults for example on seismic reflection profiles is significantly less than the amount of extension indicated by crustal thickness and thermal subsidence1 5 one mechanism suggested to account for this discrepancy is small scale faulting with offsets too small to be resolved seismically6 7 but earthquake studies8 10 indicate that small faults are responsible for only a small fraction of the total seismic moment in an active area scholz and cowie11 have recently attempted to extend this approach to the total strain at the end of a finite deformation interval by combining scaling laws describing the distributions of fault lengths and displacements here we present fault displacement data that directly conflict with scholz and cowie s conclusions and imply that up to 40 of the extension may be missed by summing fault offsets on basin profiles the fault population at the end of a long deformation interval may differ substantially from that responsible for the earthquake population at any one time

faulting of lemnos island a mirror of faulting of the north aegean trough northern greece abstract a detailed analysis of the faulting on lemnos island since the miocene was achieved by grouping the recorded meso scale faults and their slickenlines into different groups replacing them with mean representative fault planes mrfp and lineations mrfl and finding the stress tensors driven to the activation of the different mrfp mrfl pairs the oldest recognized fault activity followed the late oligocene n s contraction and uplift d1 event as the latter is implied by e w to ene wsw buckle folds in the upper eocene lower oligocene molasse type sediments it was an early middle miocene strike slip to transpression deformation d2 event associated with n s contraction that also affected the lower miocene volcanogenic rocks the next fault activity was dated in middle late miocene and caused a wnw ese extension d3 event this deformation suggests that a during the late eocene oligocene the north aegean trough was developed as a fore arc basin between the rhodopian magmatic arc and its subduction accretion complex to the south and b during the late oligocene middle miocene the north aegean trough as the whole hellenic hinterland was subjected to the transpression s l deformation and lateral extrusion because of the late collisional processes between apulia and eurasia plates and the retreating of the hellenic orogen from late miocene to pliocene a ne sw extension to right lateral transtension d4 event dominated the north aegean trough indicating that the retreating of the hellenic orogen was completely balanced by a back arc extension the deformation facilitates the westward propagation of the north anatolian fault into the north aegean sea since the early pleistocene the deformation of the north aegean trough is related to a nne ssw back arc extension d5 of the present day hellenic subduction zone and the dominant ene wsw to e w faults along the north aegean trough function as normal to oblique right lateral normal faults

diatom evidence for earthquake induced subsidence and tsunami 300 yr ago in southern coastal washington fossil diatoms from four stratigraphic sections along the tidal niawiakum river southwestern washington provide an independent paleoecological test of a relative sea level rise that has been attributed to subsidence during an inferred earthquake in the cascadia subduction zone about 300 yr ago diatom assemblages in a buried soil and overlying mud indicate a sudden and lasting shift from marshes and forests near or above highest tides to mud flats and incipient tidal marshes with a progressive return to high level tidal marshes by sediment aggradation and perhaps gradual tectonic uplift the amount of coseismic submergence required to generate the paleoecological changes observed at these sites could have ranged from a minimum of 0 8 1 0 m to a maximum of 3 0 m fossil diatoms also provide an independent test of previous inferences that the subsidence was shortly followed by a tsunami the inferred tsunami deposit is a distinct sandy interval that widely overlies the buried marsh and forest soil diatoms from this interval consist of species observed on modern sand flats of the open bay identifying a bayward source for the sand occurrences of the same sand flat species above the buried soil in the farthest up valley outcrop where a sandy interval is not recognizable suggest that the tsunami extended farther landward than was previously inferred from the stratigraphy these data rule out proposed alternatives to the coseismic subsidence model that is climatically induced sea level rise temporary submergence caused by storms and support the hypothesis that a great earthquake struck southwestern washington 300 yr ago

spatiotemporal variation of fractal properties in the source zone of the 2001 mw 7 7 bhuj earthquake the kachchh seismic zone ksz in gujarat india has been experiencing earthquakes since the occurrence of the 2001 m w 7 7 bhuj mainshock which led to a homogeneous catalog of 2808 earthquakes of m w 3 0 between 2001 and 2011 this enabled us to investigate the spatiotemporal variation of fractal dimensions d b values and seismic velocities in the ksz through 3d mapping of these three independent parameters the estimated fractal dimensions for the gedi fault gf events range from 0 7 to 1 0 whereas those of north wagad fault nwf events vary from 1 2 to 2 4 the b values for gf events also show smaller values in comparison to the nwf events the d values associated with events occurring in the main rupture zone mrz of the 2001 mainshock vary from 1 6 to 2 1 whereas those associated with events occurring in the surrounding unrifted zones show a wider range of variation from 1 2 to 2 4 we also observe that events associated with the nwf satisfy the aki s relationship d 2 b aki 1981 whereas events associated with gf do not follow this relationship both b and d values tend to increase with an increase in the earthquake density which could be connected with the process of disintegration of crustal rocks in the mrz where large material heterogeneities in terms of low and high seismic velocity patches are being mapped through local earthquake velocity tomography through examining the temporal changes in b and d values we notice several episodes of abnormally low b and d values associated with the occurrences of bursts of seismic activity in 2001 2005 2006 2008 and 2010 this decrease in b and d values is attributed to a reduction in rock friction in the causative fault zone at 10 35 km depths probably due to the presence of metamorphic fluids or volatile co2 thereby enhancing the probability of occurrence of stronger earthquakes

the evolution of seismicity at parkfield observation experiment and a fracture mechanical interpretation we compare observations of local seismicity sequences with acoustic emissions during rock fracture and find similarities in the distribution of event magnitudes which lead us to consider a model of seismicity which is characterized by fracture growth laws derived from the field of fracture mechanics and which include both negative and positive feedback processes we find that the model predicts the observed negative correlation between the seismic b value and the fractal dimension of the earthquake epicentres the simple short range interactions described in the model give rise to a system with a long range order similar to current models of critical processes

connectivity permeability and channeling in randomly distributed and kinematically defined discrete fracture network models a major use of dfn models for industrial applications is to evaluate permeability and flow structure in hardrock aquifers from geological observations of fracture networks the relationship between the statistical fracture density distributions and permeability has been extensively studied but there has been little interest in the spatial structure of dfn models which is generally assumed to be spatially random i e poisson in this paper we compare the predictions of poisson dfns to new dfn models where fractures result from a growth process defined by simplified kinematic rules for nucleation growth and fracture arrest davy et al 2010 2013 this so called kinematic fracture model is characterized by a large proportion of t intersections and a smaller number of intersections per fracture several kinematic models were tested and compared with poisson dfn models with the same density length and orientation distributions connectivity permeability and flow distribution were calculated for 3d networks with a self similar power law fracture length distribution for the same statistical properties in orientation and density the permeability is systematically and significantly smaller by a factor of 1 5 to 10 for kinematic than for poisson models in both cases the permeability is well described by a linear relationship with the areal density p32 but the threshold of kinematic models is 50 larger than of poisson models flow channeling is also enhanced in kinematic dfn models this analysis demonstrates the importance of choosing an appropriate dfn organization for predicting flow properties from fracture network parameters

a fully dynamic model of continental rifting applied to the syn rift evolution of sedimentary basins abstract a numerical technique has been developed to model dynamically lithosphere deformation and faulting the method is based on the theory of generalised functions and has been used to investigate rifting processes in a two layered lithosphere with up to four faults among other things the method allows 1 incorporation of the influence of syn rift erosion and sedimentary loading on fault growth 2 prediction of the history of individual fault development during the rift process 3 calculation of the state of stress in the lithosphere during rifting and 4 consideration of the effects of a finite value of mantle viscosity during rifting the model applied to half graben growth reveals a process that can be divided into two stages the first resulting in subsidence prior to the initiation of faulting and the second when extension exceeds a critical value seismic waves accompanying the rifting process are also predicted these and other results are compared with those obtained with other commonly employed rift basin modelling techniques

populations of faults and fault displacements and their effects on estimates of fault related regional extension abstract measured populations of fault displacements derived from regional seismic oilfield seismic coalmine plans and outcrop data show a power law distribution with exponents s of 0 45 to 0 95 for singleline samples across an array of faults the more negative values indicate relatively larger numbers of smaller faults an expression for a population of active faults derived from the gutenberg richter magnitude frequency relation for earthquakes is log n a b d log d where d maximum displacement of a fault n number of faults of maximum displacement d or greater and b d 1 0 and has the same value as b for the corresponding earthquake population populations of dead faults existing at the end of a tectonic episode have been numerically derived using a fault growth model and satisfy the relation log n a e log d where e has a value between 1 6 and 2 0 numerically derived populations of fault displacements in a dead fault population have slopes of s where s e 1 the contribution of an individual fault to the regional strain varies with the lifetime seismic moment of the fault and is proportional to d 2 estimation of fault related extension by summing heaves on faults of a limited size range is valid only if the measured size range of faults accommodates most of the extension correction can be made if the s value of the fault displacement population is known

holocene history of the el nino phenomenon as recorded in flood sediments of northern coastal peru significant precipitation along the north central coast of peru lat 5 10 s occurs exclusively during el nino incursions of warm water into the peruvian littoral flood deposits from this region therefore provide a proxy record of extreme el nino events i present a 3500 yr chronology of the extreme events based on radiocarbon dating of overbank flood sediments from the rio casma lat 9 2 s the flood plain stratigraphy suggests that the el nino phenomenon has occurred throughout the holocene and that flood events much larger than that which occurred during 1982 1983 occur here at least once every 1000 yr

source identification investigations of petroleum contaminated groundwater in the missouri ozarks abstract the growing population in the missouri ozarks rely on the abundant supply of potable groundwater found in the fractured bedrock underlying the region protection of this valuable resource from surface or near surface contamination is essential to the health and safety of the citizens of missouri petroleum products stored in underground storage tanks pose a threat to groundwater if a release occurs pools of free product of petroleum can become trapped in voids commonly found on the karst bedrock of the ozarks these pools become underground sources of contamination by slowly dissolving into the groundwater although the free product rarely travels far from the surface source dissolved phase contamination can migrate thousands of meters through underground conduits dissolved phase petroleum degasses and partitions out of the groundwater in these conduits consequently contaminated groundwater is not commonly found more than a kilometer or two few thousand feet from the source the missouri department of natural resources division of geology and land survey s leaking underground storage tank unit dgls lust investigates sites where petroleum contaminated groundwater has been found in springs or private wells but a source of the contamination is unknown these investigations start at the regional scale by determining the recharge area of the contaminated groundwater and by identifying the potentially responsible parties prps a review of dgls documents and well logs supplemented by field measurements of water levels in private wells throughout the area is used to construct a potentiometric map and determine regional groundwater flow direction water tracing is used to confirm or deny the validity accuracy of the potentiometric map and to establish hydrogeologic connections between the potential surface source of the contamination and the affected groundwater fluorescent dyes are injected into the subsurface recovered in packets containing activated carbon and analyzed by a synchronously scanning spectrofluorometer these results are compared to background fluorescence conditions established at the site prior to injection the background conditions and dye recovery results must be submitted to the missouri water trace committee for approval as an independent quality assurance quality control measure each of the prps found to be within the recharge area of the contaminated groundwater are investigated to determine the source or sources of the contamination initial field screening techniques are followed up by confirmatory sampling of soil and groundwater geophysical methods such as resistivity and electromagnetic conductivity are used to locate the bedrock surface fracture patterns and areas of extensive petroleum contamination on site drilling activities are performed at each of the prps with on site contamination screening methods such as analyzing soil gas within the borehole with a photoionization detector pid and colorimetric tubes soil samples are collected and can be analyzed on site with immunoassay kits with confirmatory samples sent to the lab temporary monitoring wells are installed in boreholes to collect on site groundwater data depth to water levels are measured and the relative elevations of the temporary wells are surveyed so that a more detailed potentiometric map can be constructed water samples are collected from the temporary wells and the boreholes are abandoned per missouri law petroleum fingerprinting by fluorescence is another tool used to investigate prps and determine the source of contamination petroleum is extracted from soil or water samples collected during on site drilling and compared to the petroleum which is extracted from a sample collected at the contaminated spring or well

the transpressive southern termination of the bucaramanga fault colombia insights from geological mapping stress tensors and fractal analysis abstract this study provides a kinematic model of the southern termination of the bucaramanga fault bf in the eastern cordillera of colombia through the integration of geological information field geology morphostructural mapping deduced stress tensors and fractal analysis minor riedel type faults are related to the main fault trace and to its southern termination in multiple structures and allow a determination of the maximum horizontal stress shm azimuth as between 105 and 140 while stress tensors linked mainly with the southern ending faults show an shm with an azimuth ranging from 108 to 169 the southern termination of the bf comprises a series of sub parallel faults that reach lengths of up to 60 km and stress tensors solutions confirm the prevalence of pure strike slip motion this set of faults constitutes a transpressive system in a restraining bend positive flower structure characterized by a domino style that captured the boyaca and soapaga faults two of the inverted structures along the axial zone of the eastern cordillera a general sinistral displacement of 23 km is assumed along the principal bf which is distributed along the southern positive flower structure with kinematics that change from strike slip in the centre to oblique slip on the lateral faults we performed fractal analysis and obtained a d value of d 1 42 0 07 for the whole area in contrast a value of d 1 37 0 08 for the northern part and d 1 39 0 12 for the southern part of the bf and taking into account the standard deviations our analysis corroborates the existence of similar faulting mechanisms and fractionation

fractal dimensions of blocks using a box counting technique for the 2001 bhuj earthquake gujarat india several destructive earthquakes have occurred in the kachchh region of gujarat during the past two centuries among them allah bund earthquake m7 8 in 1819 anjar earthquake m6 in 1956 and the recent bhuj earthquake m7 6 in 2001 the anjar earthquake was on kmf kachchh mainland fault and the recent bhuj events were caused by a hidden fault north of kmf the present study discusses the fractal analysis of tectonics governing seismic activity in the region the region has been divided into five blocks and the fractal dimension of each block has been calculated using the box counting technique the results show significantly low value of fractal dimension of the kachchh rift block consisting of the kmf compared to the other surrounding blocks which also contain faults and rifts of higher fractal dimension this indicates that the cause of earthquakes in this block may be asperities and barriers however the predominance of aftershocks over foreshocks signifies that barriers may be the main cause the other results such as the lower value of dimension of fault clustering show that the kachchh rift block has faults which are distributed in a clustered manner in this context the seismicity of this block seems to be high

a statistical scaling model for fracture network geometry with validation on a multiscale mapping of a joint network hornelen basin norway 1 fracture patterns are characterized by a complex geometry which involves a large length distribution and nonhomogeneous density distributions here we address the issue of the modeling of this complex geometry over scales through a first order model providing the characterization of the number of fractures of a given length and at a given scale we propose that the simplest model is a power law in both space and fracture length with three main parameters the exponent a of a power law length distribution the fractal dimension d which fixes the scale dependence of the number of fractures and the fracture density we verify the applicability of this model on seven fracture patterns mapped from the metric scale up to almost the kilometric scale in the hornelen basin the model efficiently describes fracture network properties at all scales with a single set of parameters for the hornelen fracture networks we found a simple relationship between basic exponents a d 1 implying that the fracture network is self similar through this analysis we present different methodological developments for deriving the basic exponents a and d and for verifying the consistency of the model overall the main methodological development is about the normalization of the measurements made from different scales of observation finally we discuss both the limitations and the uses of such a model for analyzing the hydraulic and mechanical properties of fracture networks

high resolution aquifer analog of fluvial aeolian sediments of the guarani aquifer system the guarani aquifer system gas represents one of the biggest aquifers in the world and is the most relevant groundwater resource in south america for the first time by combining field and laboratory measurements a high resolution aquifer analog model of fluvial aeolian sediments of the gas in sao paulo state brazil is constructed three parallel sections of frontal outcrops 28 m 5 8 m and two parallel sections of lateral outcrops 7 m 5 8 m are recorded during open pit mining of sandy sediments and describe in detail the three dimensional distribution of the local lithofacies and hydrofacies variations of hydraulic conductivity k and porosity n are resolved on the centimeter scale and the most permeable units of the fluvial aeolian facies association are identified the constructed aquifer analog model shows moderate hydraulic heterogeneity and a mean k value of 1 36 10 4 m s which is greater than the reported range of k values for the entire gas in sao paulo state the results suggest that the examined sedimentary unit constitutes a relevant portion of the gas in sao paulo state in the context of groundwater extraction and pollution moreover the constructed aquifer analog is considered an ideal basis for future numerical model experiments aiming at in depth understanding of the groundwater flow and contaminant transport patterns at this gas portion or at comparable fluvial aeolian facies associations

seismic imaging of the 2001 bhuj mw7 7 earthquake source zone b value fractal dimension and seismic velocity tomography studies abstract we use precisely located aftershocks of the 2001 mw7 7 bhuj earthquake 2001 2009 to explore the structure of the kachchh seismic zone by mapping the 3 d distributions of b value fractal dimension d and seismic velocities from frequency magnitude analysis we find that the catalog is complete above mw 3 0 thus we analyze 2159 aftershocks with mw 3 0 to estimate the 3 d distribution of b value and fractal dimensions using maximum likelihood and spatial correlation dimension approaches respectively our results show an area of high b d and vp vs ratio values at 15 35 km depth in the main rupture zone mrz while relatively low b and d values characterize the surrounding rigid regions and gedi fault gf zone we propose that higher material heterogeneities in the vicinity of the mrz and or circulation of deep aqueous fluid volatile co2 is the main cause of the increased b d and vp vs ratio values at 15 35 km depth seismic velocity images also show some low velocity zones continuing in to the deep lower crust supporting the existence of circulation of deep aqueous fluid volatile co2 in the region probably released from the eclogitasation of olivine rich lower crustal rocks the presence of number of high and low velocity patches further reveals the heterogeneous and fractured nature of the mrz interestingly we observe that aki 1981 s relation d 2b is not valid for the spatial b d correlation of the events in the gf d2 1 2b zone however the events in the mrz d2 1 7b show a fair agreement with the d 2b relationship while the earthquakes associated with the remaining parts of the aftershock zone d2 1 95b show a strong correlation with the aki 1981 s relationship thus we infer that the remaining parts of the aftershock zone are probably behaving like locked un ruptured zones where larger stresses accumulate we also propose that deep fluid involvement may play a key role in generating seismic activity in the mrz therefore a similar episode of deep fluid inflow could play a crucial role in causing the next strong earthquakes in the surrounding blocks of nwf

fractals in geology and geophysics the definition of a fractal distribution is that the number of objectsn with a characteristic size greater thanr scales with the relationn r d the frequency size distributions for islands earthquakes fragments ore deposits and oil fields often satisfy this relation fractals were originally introduced by mandelbrot to relate the length of a coastline to the length of the measuring stick this application illustrates a fundamental aspect of fractal distributions scale invariance the requirement of an object to define a scale in photographs of many geological features is one indication of the wide applicability of scale invariance to geological problems scale invariance can lead to fractal clustering geophysical spectra can also be related to fractals these are self affine fractals rather than self similar fractals examples include the earth s topography and geoid

scaling properties of normal faults in the central afar ethiopia and djibouti implications for strain partitioning during the final stages of continental breakup abstract the central afar depression offers an opportunity for quantitative analysis of the final stages of continental breakup at a divergent triple junction here quaternary faulting dissects plio pleistocene flood basalts providing a regionally pervasive datum to quantify the regional finite strain and fault scaling laws to this end we mapped and measured more than 8500 normal faults using remote sensing products fault length generally follows a power law distribution but exponential distributions are found in areas of magmatic extension fault throw and fault length scale following a power law relationship where t 0 031 l 0 96 similar to previous studies in afar and elsewhere in the world combining the power law distribution with this throw scaling enables a comprehensive assessment of quaternary finite strain throughout the region strain is greatest near manda inakir lake asal and the dobe hanle accommodation zone the makarassou fault zone shows low strain suggesting it does not kinematically link the manda inakir and asal rift segments the presence of moderate to high strain in the amagmatic portions of the central afar rift suggests that those areas accommodate a significant proportion of plate motion this may provide a future path for propagation between the gulf of aden rift and the red sea rift

gutenberg richter law for deep earthquakes revisited a dual mechanism hypothesis deep earthquake b values appear to vary with slab thermal state and earthquake magnitude the physical reason for the variations and the relation with deep rupture mechanisms are still unclear here i confirm the spatial variations of b value and the dependence on slab temperature using about 40 yr of data from the global centroid moment tensor catalog a new bimodal pattern is observed for the 500 700 km depth range b is close to 1 in the cold tonga slab while in warmer slabs e g south america japan kuril izu bonin mariana b is close to 0 5 for intermediate magnitudes m w 5 3 6 5 and increases to 1 for large magnitudes m w 6 5 to explain these observations i propose a dual mechanism hypothesis in which deep earthquakes nucleate only within the metastable olivine wedge mow but can rupture outside mow by a different mechanism the fractal dimension of earthquake size distribution changes from 2 to 1 as the thermally controlled mow thickness decreases and back to 2 as the mechanism outside mow dominates

geologic setting field survey and modeling of the chimbote northern peru tsunami of 21 february 1996 whereas the coast of peru south of 10 s is historically accustomed to tsunamigenic earthquakes the subduction zone north of 10 s has been relatively quiet on 21 february 1996 at 21 51 gmt 07 51 local time a large tsunamigenic earthquake harvard estimate m w 7 5 struck at 9 6 s 79 6 w approximately 130 km off the northern coast of peru north of the intersection of the mendana fracture zone with the peru chile trench the likely mechanism inferred from seismic data is a low angle thrust consistent with subduction of the nazca plate beneath the south american plate with relatively slow rupture characteristics approximately one hour after the main shock a damaging tsunami reached the peruvian coast resulting in twelve deaths we report survey measurements from 7 7 s to 11 s on maximum runup 2 5 m between 8 and 10 s maximum inundation distances which exceeded 500 m and tsunami sediment deposition patterns observations and numerical simulations show that the hydrodynamic characteristics of this event resemble those of the 1992 nicaragua tsunami differences in climate vegetation and population make these two tsunamis seem more different than they were this 1996 chimbote event was the first large m w 7 subduction zone interplate earthquake between about 8 and 10 s in peru since the 17th century and bears resemblance to the 1960 m w 7 6 event at 6 8 s together these two events are apparently the only large subduction zone earthquakes in northern peru since 1619 est latitude 8 s est m w 7 8 these two tsunamis also each produced more fatalities than any other tsunami in peru since the 18th century we concur with pelayo and wiens 1990 1992 that this subduction zone in northern peru resembles others where the subduction zone is only weakly coupled and convergence is largely aseismic subduction zone earthquakes when they occur are slow commonly shallow and originate far from shore near the tip of the wedge thus they are weakly felt and the ensuing tsunamis are unanticipated by local populations although perhaps a borderline case the chimbote tsunami clearly is another wake up example of a tsunami earthquake

terminal classic drought in the northern maya lowlands inferred from multiple sediment cores in lake chichancanab mexico we present new density records from sediment cores taken along a depth transect in lake chichancanab mexico the data reveal in great detail the climatic events that comprised the terminal classic drought tcd and coincided with the demise of classic maya civilization between ca 750 and 1050 ad in shallow water cores the tcd is marked by a condensed gypsum horizon in deeper water sections it is expanded and represented by numerous interbedded gypsum and organic rich strata the tcd was not a single two century long megadrought but rather consisted of a series of dry events separated by intervening periods of relatively moister conditions we estimate the tcd occurred between ca 770 and 1100 ad and included an early phase ca 770 870 ad and late phase ca 920 1100 ad the intervening 50 year period ca 870 920 ad was relatively moister each dry phase is represented by multiple gypsum density bands interbedded with organic rich sediment that indicate alternating dry and wet conditions spectral analysis revealed significant periods around 213 50 and 27 years despite uncertainty regarding the ages of these events their pattern is robust and generally consistent with other proxy records under the same climate regime such as the marine cariaco basin off northern venezuela science 299 2003 1731

investigating the geoelectrical response of hydrocarbon contamination undergoing biodegradation 1 a newly proposed geoelectrical model for hydrocarbon contaminated sites predicts high conductivities coincident with the contaminated zone as opposed to the traditionally accepted low conductivity the model attributes the high conductivities to mineral weathering resulting from byproducts of microbial redox processes to evaluate this conductive model in situ vertical conductivity measurements were acquired from a light non aqueous phase liquid lnapl contaminated site the results showed high conductivities coincident with the zone of contamination and within the smear zone influenced by seasonal water table fluctuations we infer this zone as an active zone of biodegradation and suggest significant microbial degradation under partially water saturated conditions a simple archie s law analysis shows large pore water conductivities necessary to reproduce the bulk conductivity measured at the contaminated location this study supports the conductive layer model and demonstrates the potential of geoelectrical investigations for assessing microbial degradation of lnapl impacted soils

el nino southern oscillation events recorded in the stratigraphy of the tropical quelccaya ice cap peru snow accumulation measured during 1982 1983 on the quelccaya ice cap peru was 70 percent of the average from 1975 through 1983 inspection of 19 years 1964 through 1983 of accumulation measured near the summit of quelccaya reveals a substantial decrease 30 percent in association with the last five el nino southern oscillation enso occurrences in the equatorial pacific the enso phenomenon is now recognized as a global event arising from large scale interactions between the ocean and the atmosphere understanding this extreme event with the goal of prediction requires a record of past occurrences the quelccaya ice cap which contains 1500 years of annually accumulated ice layers may provide a long and detailed record of the most extreme enso events

southward movement of the pacific intertropical convergence zone ad 1400 1850 tropical rainfall patterns control the subsistence lifestyle of more than one billion people seasonal changes in these rainfall patterns are associated with changes in the position of the intertropical convergence zone which is characterized by deep convection causing heavy rainfall near 10 n in boreal summer and 3 n in boreal winter dynamic controls on the position of the intertropical convergence zone are debated but palaeoclimatic evidence from continental asia africa and the americas suggests that it has shifted substantially during the past millennium reaching its southernmost position some time during the little ice age ad1400 1850 however without records from the meteorological core of the intertropical convergence zone in the pacific ocean quantitative constraints on its position are lacking here we report microbiological molecular and hydrogen isotopic evidence from lake sediments in the northern line islands galapagos and palau indicating that the pacific intertropical convergence zone was south of its modern position for most of the past millennium by as much as 500km during the little ice age a colder northern hemisphere at that time possibly resulting from lower solar irradiance may have driven the intertropical convergence zone south we conclude that small changes in earth s radiation budget may profoundly affect tropical rainfall

recurrence models and parkfield california earthquakes main shocks of the earthquake sequences that occurred on the parkfield section of the san andreas fault in central california in 1922 1934 and 1966 are characterized by southeast rupture expansion over the same 20 to 30 km long section of the fault whereas the seismic moments for the 1922 and 1934 events are identical to within a precision of 10 the seismic moment for 1966 is 20 greater than for the earlier events to within a precision of 20 the parkfield area seismicity in general seems well described by a recurring moderate size characteristic earthquake repeating the same epicenter magnitude seismic moment rupture area and southeast direction of rupture expansion an unexplained 10 year advance of the 1934 event is the only discrepancy in the hypothesis that the parkfield earthquakes in 1857 1881 1901 1922 1934 and 1966 represent a strictly periodic process assuming the strictly periodic model and the absence since 1966 of the perturbations hypothesized for the 1922 to 1934 period the next characteristic parkfield earthquake should occur between 1983 and 1993

diatom assemblages in tsunami deposits associated with the 2004 indian ocean tsunami at phra thong island thailand abstract diatom assemblages in sandy deposits of the 2004 tsunami at phra thong island thailand may provide clues to flow conditions during the tsunami the tsunami deposits contain one or more beds that fine upward commonly from medium sand to silty very fine sand diatom assemblages of the lowermost portion of the deposit predominantly comprise unbroken beach and subtidal species that live attached to sand grains the dominant taxa shift to marine plankton species in the middle of the bed and to a mix of freshwater brackish and marine species near the top these trends are consistent with expected changes in current velocities of tsunami through time during high current velocities medium sand is deposited only beach and subtidal benthic diatoms attached to sediment can be incorporated into the tsunami deposit high shear velocity keeps finer material including planktonic diatoms in suspension with decreasing current velocities finer material including marine plankton can be deposited finally during the lull between tsunami waves the entrained freshwater brackish and marine species settle out with mud and plant trash low numbers of broken diatoms in the lower medium sand implies rapid entrainment and deposition whilst selective breakage of marine plankton thalassionema nitzschioides and thalassiosira and coscinodiscus spp in the middle portion of the deposit probably results from abrasion in the turbulent current before deposition

tectonics fracturing of rock and erosion 1 we argue that by fracturing rock not by raising it relative to base level tectonics plays its most important role in causing rapid incision of valleys and rapid erosion of hillslopes tectonic deformation riddles the upper crust with fractures which not only provide avenues for water flow and thus promote weathering and further disintegration of rock but also fragment bedrock into debris that is readily extracted and transported by surface processes bends in active faults require straining of adjacent rock masses aftershocks that occur subsequent to slip on primary faults reflect penetrative brittle deformation of the upper crust at least some aftershocks must nucleate or lengthen cracks which contribute to the comminution of these rock masses scaling rules suggest that dimensions of ruptures for very small m 2 earthquakes can be meters or less the gutenberg richter recurrence relationship implies that such earthquakes are common as high magnification seismographs in low noise environments confirm moreover large differences among fault plane solutions for aftershocks show that the small faults on which they occur are not parallel to one another some faults must intersect thus the upper crust in tectonically active regions should be fragmented into blocks down to the scale of boulders or smaller dismembered rock arrives at the earth s surface already prepared to be transported away as a corollary both deeply exhumed lower crust and posttectonic igneous rock never deformed under brittle conditions and not deformed recently should be less susceptible to detachment and subsequent transport than fractured rock

evidence for three north sea tsunamis at the shetland islands between 8000 and 1500 years ago abstract coastal fen and lake deposits enclose sand layers that record at least three holocene tsunamis at the shetland islands the oldest is the well known storegga tsunami ca 8100 cal yr bp which at the shetlands invaded coastal lakes and ran up peaty hillsides where it deposited sand layers up to 9 2 m above present high tide level because sea level at ca 8100 cal yr bp was at least 10 15 m below present day sea level the runup exceeded 20 m in two lakes we also found deposits from a younger tsunami dated to ca 5500 cal yr bp the sediment facies are similar to those of the storegga tsunami rip up clasts sand layers re deposited material and marine diatoms runup was probably more than 10 m yet another sand layer in peat outcrops dates to ca 1500 cal yr bp this sand layer thins and fines inland and was found at two sites 40 km apart and traced to ca 5 6 m above present high tide the oldest tsunami was generated by the storegga slide on the norwegian continental slope we do not know what triggered the two younger events

a model of damage mechanics for the deformation of the continental crust 1 we derive a continuum rheology for the deformation of the continental crust using continuum damage mechanics it is hypothesized that when a constant strain rate is applied to a solid material the stress and damage increase until failure occurs which is analogous to an earthquake we further assume that this process is repeated in analogy to the reoccurrence of earthquakes on a fault our model assumes that the continental crust behaves elastically below a yield stress y above this stress the continuum deformations can be modeled as a non newtonian viscous flow with y n where n is constant we derive the modified omori s law for aftershock decay using a viscoelastic version of our model and get good agreement with observations taking n 6 using parameter values appropriate for aftershocks we obtain a continuum crustal rheology that can explain major orogenies such as the indian asian collision

diatoms as an aid in identifying late holocene tsunami deposits diatoms bacillariophyta help identify the onshore deposits of tsunamis from earthquakes on the cascadia subduction zone along the pacific coast of oregon washington and british columbia and on faults high in the north american plate in the puget sound area of washington at the copalis river washington diatom analyses suggest that a tsunami deposit about 300 calendric years old 300 yr bp originated from sandy shoals of the lower estuary rather than nearby beaches or coastal dunes at cultus bay and west point washington well preserved benthic estuarine diatoms in sand sheets overlying tidal marsh peat indicate that the deposits came from intertidal or nearshore areas of puget sound on an abruptly uplifted mudflat at the landward end of hood canal at lynch cove washington tidal flat diatoms refute the possibility of a terrestrial source for the sand diatoms in 300 yr bp tsunami deposits on the niawiakum river washington confirm that the sand in these deposits had a marine source and help

climate variability on the yucatan peninsula mexico during the past 3500 years and implications for maya cultural evolution climate variability on the yucatan peninsula during the past 3500 yrs is reconstructed from the measurement of 18o in monospecific ostracods and gastropods in a 6 3 m sediment core from lake punta laguna mexico this late holocene record is divided into three periods based on changes in mean 18o values from 3310 to 178514c yr b p period i low mean 18o values indicate relatively wet conditions i e low evaporation to precipitation ratio e p mean oxygen isotopic values increased 178514c yr b p and the interval between 1785 and 93014c yr b p period ii was distinctly drier than the periods before or after the climate during the latter part of period ii was persistently dry with exceptionally arid events centered at 1171 1019 and 94314c yr b p equivalent to 862 986 and 1051 a d this interval of frequent drought was recorded at several other localities in mexico and central america and coincided with the collapse of classic maya civilization following the last arid event 18o values decreased abruptly at 93014c yr b p beginning of period iii signaling a return to wetter conditions that have generally prevailed to the present with the exception of a dry episode centered at 55914c yr b p 1391 a d the paleoclimatic record from punta laguna provides evidence that multi decadal and millennial scale changes ine poccurred on the yucatan peninsula during the late holocene these wet dry episodes may have influenced cultural evolution in mesoamerica

temporal and spatial variations of gutenberg richter parameter and fractal dimension in western anatolia turkey abstract the temporal and spatial variations of gutenberg richter parameter b value and fractal dimension dc during the period 1900 2010 in western anatolia was investigated the study area is divided into 15 different source zones based on their tectonic and seismotectonic regimes we calculated the temporal variation of b and dc values in each region using zmap the temporal variation of these parameters for the prediction of major earthquakes was calculated the spatial distribution of these parameters is related to the stress levels of the faults we observed that b and dc values change before the major earthquakes in the 15 seismic regions to evaluate the spatial distribution of b and dc values 0 50 0 50 grid interval were used the b values smaller than 0 70 are related to the aegean arc and eskisehir fault the highest values are related to sultandagi and sandikli faults fractal correlation dimension varies from 1 65 to 2 60 which shows that the study area has a higher dc value the lowest dc values are related to the joining area between aegean and cyprus arcs burdur fethiye fault zone some have concluded that b values drop instantly before large shocks others suggested that temporally stable low b value zones identify future large earthquake locations the results reveal that large earthquakes occur when b decreases and dc increases suggesting that variation of b and dc can be used as an earthquake precursor mapping of b and dc values provide information about the state of stress in the region i e lower b and higher dc values associated with epicentral areas of large earthquakes

paleoenvironmental catastrophies on the peruvian coast revealed in lagoon sediment cores from pachacamac abstract paleoenvironmental reconstruction combining data from diatom pollen macrophytic and archaeological analyses had not been attempted previously for coastal peru we analyzed two radiocarbon dated sediment cores extracted from the sacred urpi kocha lagoon at the pre hispanic religious center of pachacamac ca ad 350 1533 near lima to characterize the paleoenvironment of the site the data reveal an environmental history characterized by alternating periods of severe drought and catastrophic flood recurrent pulses with distinctive sediment diatom pollen and macrophytic characteristics reflecting variations in water depth substrate turbidity and salinity usually contain a thick basal sandy storm deposit overlain by thin organic accumulations of peat gyttja and snails the most intense of these disturbance pulses when correlated with pollen plant macrofossils radiocarbon dates and regional proxy data provide local evidence of four major floods associated with sustained catastrophic el nino events tsunamis and or severe storms in the andean highlands over the last 2000 years

geophysical investigation using resistivity and gpr methods a case study of a lubricant oil waste disposal area in the city of ribeirao preto sao paulo brazil geophysics has been shown to be effective in identifying areas contaminated by waste disposal contributing to the greater efficiency of soundings programs and the installation of monitoring wells in the study area four trenches were constructed with a total volume of about 25 000 m3 they were almost totally filled with re refined lubricating oil waste for approximately 25 years no protection liners were used in the bottoms and laterals of the disposal trenches the purpose of this work is to evaluate the potential of the resistivity and ground penetrating radar gpr methods in characterizing the contamination of this lubricant oil waste disposal area in ribeirao preto sp situated on the geological domain of the basalt spills of the serra geral formation and the sandstones of the botucatu formation geophysical results were shown in 2d profiles the geophysical methods used enabled the identification of geophysical anomalies which characterized the contamination produced by the trenches filled with lubricant oil waste conductive anomalies smaller than 185 m immediately below the trenches suggest the action of bacteria in the hydrocarbons as has been observed in several sites contaminated by hydrocarbons in previously reported cases in the literature it was also possible to define the geometry of the trenches as evidenced by the gpr method direct sampling chemical analysis of the soil and the water in the monitoring well confirmed the contamination in the soil analysis low concentrations of several polycyclic aromatic hydrocarbons pahs were found mainly naphthalene and phenanthrene in the water samples an analysis verified contamination of the groundwater by lead pb the geophysical methods used in the investigation provided an excellent tool for environmental characterization in this study of a lubricant oil waste disposal area and could be applied in the study of similar areas

modelling of earthquake rupturing as a stochastic process and estimation of its distribution function from earthquake observations summary the effect on earthquake rupturing of heterogeneities in tectonic stress and in material strength along a large fault zone is incorporated in the potential dynamic stress drop defined as the difference between the tectonic shear stress and the dynamic frictional strength according to a slip weakening model the distribution of the potential dynamic stress drop az x along the strike of the fault plane is modelled as a 1 d stochastic process using a simple dynamic fracture criterion a relation is established between earthquake rupturing and potential dynamic stress drop by which any earthquake rupture process can be regarded as a segment of a realization of the process at where azd x 0 since dynamic slip varies approximately linearly with dynamic stress drop it has the same distribution function as azd x provided that azd x is a gaussian process three independent earthquake observations i e the average stress drop the gutenberg richter relation and the surface slip along earthquake faults are used to estimate the distribution function of azd x an analytical solution is derived for the distribution function of azd x which shows that among all known distribution models only the fractional brownian motion with index h 0 fractal dimension d 2 in the 1 d case can give rise to the observed approximately constant stress drop independent of earthquake size the probability distribution of the size of zerosets of the fractional brownian motion shows a power law relation with frequency which resembles the frequency seismic moment relation using an average b value of 1 o for small earthquakes an index h o of the fractional brownian motion is obtained the model predicts that the b value for large earthquakes is smaller than that for small earthquakes along the same fault zone which is in agreement with observations the surface slip data of two strike slip dominated earthquake faults with rupture lengths larger than 100 km are inverted using power spectral analysis both data sets display a power law relation between the sample power spectrum and the spatial frequency which implies a fractional brownian distribution the estimated index h is close to zero for both earthquake faults stress drops b values and surface slips all independently suggest that the earthquake rupturing process can be modelled stochastically as a fractional brownian motion with index h 0

spatial variations of the fractal properties of seismicity in the anatolian fault zones abstract the anatolian fault zones are seismically active strike slip fault zones transcending the anatolian plate in e w and n s directions we investigate the spatial variations of seismicity along these zones in an attempt to investigate fault complexity along strike quantified by the gutenberg richter b value and the fractal correlation dimension of earthquake epicentres using the maximum likelihood method and the correlation integral respectively the investigation covers instrumentally recorded carthquakes of magnitude m 4 5 occurring between 1900 and 1992 we find systematic spatial variations which may be related to structural or mechanical variability along strike in particular the large change in strike at the northern apex of the north anatolian fault zone is associated with the highest correlation dimension and lowest b value for seismicity this century the correlation dimension and b value show a negative correlation with respect to each other similar to results reported in other regional studies of japan and southern california this statistical correlation is stronger when more objective seismic zoning is carried out based on number of events rather than more subjective seismotectonic zoning in common use in seismic hazard analysis

a new fractal approach to the clustering of earthquakes physical fractal abstract traditional fractal analysis methods of earthquake temporal clustering treat earthquake events as mathematical points without mass in time smalley et al 1987 the results obtained by these methods mainly reflect the seismic behavior of numerous small earthquakes a sieve method of physical fractal analysis has been developed in the present article in which a series of magnitude sieves are used to study the fractal behavior of earthquakes with different magnitudes fractal analyses of earthquake clustering are conducted for three regions northern china mainland of china and southern california we find that all the earthquake subsets of each region show nearly the same fractal dimension d 0 3 for northern china and the mainland of china and d 0 4 for southern california the scaling ranges in which the corresponding earthquake subsets under consideration exhibit fractal features vary from subset to subset the method has the potential application to characterizing the fractal behavior of earthquake clustering for different regions

spatio temporal seismicity patterns using mutual information application to southern iberian peninsula spain earthquakes abstract a quantitative method to characterize the spatio temporal evolution of the seismic activity of a region for a given time interval is proposed in this paper the epicentral region is divided in equal area parallelograms that we call cells a probability p i is assign to every cell depending on its seismic activity level the evolution of the mutual information based on these probabilities allows us to fit the optimal value for p i s the analysis results show that is possible to monitor the change of seismic activity quantitatively we show that a propagation model based on cross template model ct model give us a criteria whether or not an area whose size is determined by the model mathematically is going to be considered seismically activated in a period of time whose value is also the result of the application of the method our method is applied to the data of southern iberian peninsula seismicity including more than 10 000 earthquakes data available from the andalusian seismic network is used from 1985 to 1995

evolving geometrical heterogeneities of fault trace data summary we perform a systematic comparative analysis of geometrical fault zone heterogeneities using derived measures from digitized fault maps that are not very sensitive to mapping resolution we employ the digital gis map of california faults version 2 0 and analyse the surface traces of active strike slip fault zones with evidence of quaternary and historic movements each fault zone is broken into segments that are defined as a continuous length of fault bounded by changes of angle larger than 1 measurements of the orientations and lengths of fault zone segments are used to calculate the mean direction and misalignment of each fault zone from the local plate motion direction and to define several quantities that represent the fault zone disorder these include circular standard deviation and circular standard error of segments orientation of long and short segments with respect to the mean direction and normal separation distances of fault segments we examine the correlations between various calculated parameters of fault zone disorder and the following three potential controlling variables cumulative slip slip rate and fault zone misalignment from the plate motion direction the analysis indicates that the circular standard deviation and circular standard error of segments decrease overall with increasing cumulative slip and increasing slip rate of the fault zones the results imply that the circular standard deviation and error quantifying the range or dispersion in the data provide effective measures of the fault zone disorder and that the cumulative slip and slip rate or more generally slip rate normalized by healing rate represent the fault zone maturity the fault zone misalignment from plate motion direction does not seem to play a major role in controlling the fault trace heterogeneities the frequency size statistics of fault segment lengths can be fitted well by an exponential function over the entire range of observations

fractals in studies of faulting and seismicity in the baikal rift zone abstract fractal analyses have been carried out for spatial patterns of faulting including over 3000 faults and seismicity of more than 60 000 earthquakes in the baikal rift zone brz it is concluded that faulting and seismicity are in balance in the whole brz and out of balance in its flanks by analysing fractal dimensions of seismicity in time it has been revealed that the out of balance state of the processes is predetermined by the fact that development of the spatial patterns of epicentral fields has not been completed yet in the brz flanks

great earthquakes and subduction along the peru trench subduction along the peru trench between 9 and 15 s involves both large interplate underthrusting earthquakes and intraplate normal fault earthquakes the four largest earthquakes along the peru trench are from north to south the 1970 m 7 9 intraplate normal fault earthquake and the interplate underthrusting earthquakes in 1966 m 8 0 1940 m 8 and 1974 m 8 0 we have studied the rupture process of these earthquakes and can locate spatial concentrations of moment release through directivity analysis of source time functions deconvolved from long period p wave seismograms the 1966 earthquake has a source duration of 45 s with most of the moment release concentrated near the epicenter two intraplate normal fault events occurred in 1963 m 6 7 and 7 0 at the down dip edge of the 1966 dominant asperity the 1940 earthquake is an underthrusting event with a simple source time function of 30 s duration that represents the rupture of a single asperity near the epicenter the 1974 earthquake has a source duration of 45 50s and two pulses of moment release this earthquake has a bilateral rupture with the first pulse of moment release located northwest of the epicenter and the second pulse of moment release located southeast of the epicenter both pulses of moment release occur on the northern half of the aftershock area the 1970 earthquake is one of the largest intraplate normal fault earthquakes to occur in a subduction zone and has a moment release comparable with many large underthrusting events the aftershocks for the 1970 earthquake form two distinct clusters the smaller cluster near the epicenter has focal mechanisms characterized by down dip tension but the second aftershock cluster located 80 km southeast of the epicenter has focal mechanisms characterized by down dip compression the p waves for the main shock can be modeled as two sources with different focal mechanisms and depths similar to the two clusters of aftershocks the first event has a down dip tensional focal mechanism and is followed 40 s later by a distinct second event located 80 km southeast of the epicenter with a down dip compressional focal mechanism and a somewhat shallower depth than the first event the observable directivity indicates that the second source is located at the second cluster of aftershocks that have down dip compressional focal mechanisms the occurrence of both down dip tensional and compressional focal mechanisms may be explained by extreme unbending stresses associated with the anomalous slab geometry the unusually large size of the 1970 earthquake may also be related to the subduction of the mendana fracture zone the historic earthquake record along the peru trench indicates that the previous event in 1746 was much larger than any of the three underthrusting earthquakes this century the 1746 earthquake may have ruptured the entire segment in a multiple asperity earthquake thus the mode of rupture along the peru coast has changed between successive earthquake cycles

frequency size distribution of competent lenses in a block in matrix melange imposed length scales of brittle deformation 1 this study explores the frequency size distribution of competent lenses phacoids in the chrystalls beach complex a melange shear zone within the otago schist accretion collision assemblage new zealand the distribution of phacoids within a cleaved pelitic matrix follows a power law distribution with exponent 1 18 d 2 37 2 d at outcrop scale whereas distributions at thin section scale have higher d than the outcrop they were sampled from d relates to volume fraction and distribution of competent material where high d correlates with small aspect ratio phacoids and high matrix volume fraction in outcrops which experienced mixed continuous discontinuous deformation d 1 4 0 2 it is suggested that d 1 4 indicates dominant continuous deformation whereas d 1 4 is indicative of localized deformation on shear discontinuities in this melange d therefore appears a function of dominant deformation style actively deforming melange shear zones likely exhibit a range of seismic styles and earthquake magnitudes at length scales limited by lithological layering and shear zone thickness a hypothesis is suggested where strongly coupled shear zone segments may be distinguished by a high volume fraction of competent material low d while aseismically creeping regions are characterized by a high proportion of incompetent rock high d as the b value in the gutenberg richter frequency magnitude relationship also tends to be high in coupled and low in creeping fault segments it may be that d is analogous to b and the b value is also related to the ratio of incompetent competent material and dominant fault zone deformation style

fractal geometry of faults and seismicity of koyna warna region west india using landsat images the koyna warna region has been shaken by several earthquakes greater than magnitude 4 in the last 35 years four of them in 1967 1973 1980 and 1993 were potentially very destructive with magnitudes exceeding 5 0 the majority of seismic events recorded to date has been induced from koyna warna reservoir areas this paper discusses the fractal analysis of a fault map from landsat images with the increasing seismic activity in the region the region is divided into six blocks and the fractal dimension of each block is calculated using a box counting technique a plot of a three dimensional map of the fractal dimension is prepared it shows that the value of the fractal dimension is gently dipping from ne to sw the fractal dimension is used to estimate the b value in the frequency magnitude relation of earthquakes in the region which is in agreement with earlier studies

on the fractal dimension of the fallout deposits a case study of the 79 a d plinian eruption at mt vesuvius we investigated the existence of a fractal law power law distribution of size pyroclastic fragments erupted during the fallout phase of the 79 a d plinian eruption at mt vesuvius in particular we performed a particle size distribution analysis on 18 white and grey pumice samples collected in six sites distributed in the sw sector of mt vesuvius our measurements show that the fragmentation of samples in the investigated range from 32 mm to 850 m follows a power law guaranteeing the scale invariance of the process the relationship frequency size distribution of the fragments is verified independently from the nature i e pumices and lithics and stratigraphic height of the considered samples in the pyroclastic deposit therefore the fractal fragmentation theory can be indicated for evaluating the relationship between the intensity of fragmentation fractal dimension d and eruption energy in this way the apparent chaotic distribution of the particles in the fallout deposits hides a self organized complexity revealed by the retrieved power law distribution we further remark that a key aspect of our analysis is the founded evidence that the fractal dimension of the lithics is systematically greater than that of the pumices

fractal dimension of the 1999 chamoli earthquake from aftershock studies in garhwal himalaya the aftershock sequence of chamoli earthquake mw 6 4 of 29 march 1999 is analyzed to study the fractal structure in space time and magnitude distribution the b value is found to be 0 63 less than which is usually observed worldwide and in the himalayas this indicates that the numbers of smaller earthquakes are relatively less than the larger ones the spatial correlation is 1 64 indicating that events are approaching a two dimensional region meaning that the aftershocks are uniformly distributed along the trend of the aftershock zone temporal correlation is 0 86 for aftershocks of m 1 indicating a nearly continuous aftershock activity however it is 0 5 for aftershocks of m 1 75 indicating a non continuous aftershock activity from the assessment of slip on different faults it is inferred that 70 displacement is accommodated on the primary fault and the remainder on secondary faults

a fractal approach to probabilistic seismic hazard assessment abstract the definition of a fractal distribution is that the number of objects events n with a characteristic size greater than r satisfies the relation n r d where d is the fractal dimension the applicability of a fractal relation implies that the underlying physical process is scale invariant over the range of applicability of the relation the empirical frequency magnitude relation for earthquakes defining a b value is a fractal relation with d 2b accepting the fractal distribution the level of regional seismicity can be related to the rate of regional strain and the magnitude of the largest characteristic earthquake high levels of seismic activity indicate either a large regional strain or a low magnitude maximum characteristic earthquake or both if the regional seismicity has a weak time dependence the approach can be used to make probabilistic seismic hazard assessments as in many fractal applications the basic approach has been used in the past however the association of a fractal behavior with scale invariance provides a rational basis for the extrapolation of frequency magnitude statistics in order to make predictions of seismic hazards

geology and mathematics progressing mathematization of geology surveying the history of mathematical geology since the times of lyell it is shown that its characteristic feature is that of interaction between a strongly historically inclined science and rather abstract mathematics statistics it is proven that mathematization of geology and experimental geology stimulate one another and that mathematical geology can be of essential aid in formulating conceptual models and scientific theories to integrate and unify diverse geological phenomena

fault kinematics of the magallanes fagnano fault system southern chile an example of diffuse strain and sinistral transtension along a continental transform margin abstract a system of left lateral faults that separates the south american and scotia plates known as the magallanes fagnano fault system defines the modern tectonic setting of the southernmost andes and is superimposed on the late cretaceous paleogene patagonian fold thrust belt fault kinematic data and crosscutting relationships from populations of thrust strike slip and normal faults from peninsula brunswick adjacent to the magallanes fagnano fault system presented herein show kinematic and temporal relationships between thrust faults and sets of younger strike slip and normal faults thrust fault kinematics are homogeneous in the study area and record subhorizontal northeast directed shortening strike slip faults record east northeast directed horizontal shortening west northwest directed horizontal extension and form riedel and p shear geometries compatible with left lateral slip on the main splay of the magallanes fagnano fault system normal faults record north south trending extension that is compatible with the strike slip faults the study area occurs in a releasing step over between overlapping segments of the magallanes fagnano fault system which localized on antecedent sutures between basement terranes with differing geological origin results are consistent with regional tectonic models that suggest sinistral shearing and transtension in the southernmost andes was contemporaneous with the onset of seafloor spreading in the western scotia sea during the early miocene

regional variations and correlations of gutenberg richter parameters and fractal dimension for the different seismogenic zones in western anatolia we investigated the regional variations of gutenberg richter g r parameters a and b and fractal correlation dimension dc and relations among these parameters for the different regions in western anatolia wa the whole examined area 26 33 e 33 40 5 n is divided into 15 different seismogenic regions based on their tectonic and seismotectonic regimes we used database including 69 182 earthquakes for the instrumental period from 1900 to 2011 we calculated b value which is the slope of the frequency magnitude gutenberg richter relationship from maximum likelihood method ml and dc value which is the slope of log10c r versus log10r from correlation integral using the least squares ls method computed values for 15 different seismogenic regions are mapped using different color scale for different range of values of b and dc regional distributions of these parameters reveal information about regional variation of stress level and geological complexity we concluded aegean arc and aegean islands aliaga fault and buyuk menderes graben the most vulnerable regions for occurrence of the large earthquakes in wa considering the computed lowest b values and the highest dc values in these regions since dc b values are the highest in these regions this ratio may be used as an indicator of earthquake hazard levels of different seismogenic zones in a studied region an effort is made to find relationships between the g r parameters and fractal dimension we observed negative correlation between dc and b values and positive correlation between dc and a b values for different regions of wa we observed that the relationship between a b and dc can be used for seismicity earthquake risk and hazard studies because of the computed high correlation coefficient and fewer scattering of these parameters

evidence for chaotic behaviour in seismic wave scattering scattering of seismic waves by lithospheric heterogeneities produces seismic coda which typically look random consequently stochastic modelling methods are usually applied to these coda 1 6 here we introduce a technique based on previous work 7 for evaluating the predictability of time series data as an indicator of underlying determinism when analyzed using this method both earthquake and explosive source seismic coda display strong short term predictability which is not consistent with a random generation mechanism

earthquake scaling relations for mid ocean ridge transform faults 1 a mid ocean ridge transform fault rtf of length l slip rate v and moment release rate can be characterized by a seismic coupling coefficient ae at where ae v is an effective seismic area and at l3 2v 1 2 is the area above an isotherm tref a global set of 65 rtfs with a combined length of 16 410 km is well described by a linear scaling relation 1 ae at which yields 0 15 0 05 for tref 600 c therefore about 85 of the slip above the 600 c isotherm must be accommodated by subseismic mechanisms and this slip partitioning does not depend systematically on either v or l rtf seismicity can be fit by a truncated gutenberg richter distribution with a slope 2 3 in which the cumulative number of events n0 and the upper cutoff moment mc dcac depend on at data for the largest events are consistent with a self similar slip scaling dc ac1 2 and a square root areal scaling 2 ac at1 2 if relations 1 and 2 apply then moment balance requires that the dimensionless seismic productivity 0 0 atv should scale as 0 at 1 4 which we confirm using small events hence the frequencies of both small and large earthquakes adjust with at to maintain constant coupling rtf scaling relations appear to violate the single mode hypothesis which states that a fault patch is either fully seismic or fully aseismic and thus implies ac ae the heterogeneities in the stress distribution and fault structure responsible for relation 2 may arise from a thermally regulated dynamic balance between the growth and coalescence of fault segments within a rapidly evolving fault zone

taking into account the complexity of natural fracture systems in reservoir single phase flow modelling abstract in order to develop a methodology for reservoir flow modelling that takes into account the complexity of natural fracture systems high quality fracture datasets were collected at different scales in a well exposed clastic formation at tayma saudi arabia and used to design a multiscale fracture model incorporating both large scale faults and medium to small scale fractures joints for numerical simulation flow modelling was then conducted taking into account three scales of permeability to represent the matrix joints and faults actually the most severe situation was considered where the permeability of the joints dominates strongly the one of the matrix the results obtained with this model show that on a local scale the maximum directional flow is always horizontal along the direction of a systematic joint set in this case nw se vertical flow is only possible where joints j and bedding planes b have conductivity ratios c j c b between 0 1 and 10 the flow properties of the model were then upscaled to simulate the entire reservoir through combining the flow properties of the jointed matrix represented by an equivalent permeability tensor with those of the large scale fault system which was modelled explicitly in a dual permeability system simulation of a pumping well to illustrate the hydraulic response of the multiscale fracture system according to different permeability ratios between the faults and the jointed rock matrix i e k f k m showed that the influence of the fault system begins to be visible at a permeability ratio of 100 at a ratio of 10 000 the hydraulic potential field is controlled completely by the fault system the fault planes becoming isopotential lines of the hydraulic field this multiscale fracture flow simulation procedure which combines the hydraulic effects of small to medium scale fractures and large scale faults could be very helpful in predicting flow responses in dual permeability reservoirs

a correlation between the b value and the fractal dimension from the aftershock sequence of the 1999 chi chi taiwan earthquake summary we analyse large number of aftershock events from the 1999 chi chi taiwan earthquake m l 7 3 recorded around the epicentre area of the main shock in central taiwan where events can be precisely located due to dense coverage of modern seismometers the seismicity is characterized by the b value of the gutenberg richter relation and the fractal correlation dimension d of earthquake hypocenters calculated from sliding windows containing more than 100 events over a span of 6 months after the main shock we find a positive correlation between b and d from the aftershock sequence our result thus suggests that aki s relation d 3b c could be possibly applied to one single fracturing process and its related aftermath

ground penetrating radar for high resolution mapping of soil and rock stratigraphy ground penetrating radar is a technique which offers a new way of viewing shallow soil and rock conditions the need to better understanding overburden conditions for activities such as geochemical sampling geotechnical investigations and placer exploration as well as the factors controlling groundwater flow has generated an increasing demand for techniques which can image the subsurface with higher resolution than previously possible the areas of application for ground penetrating radar are diverse the method has been used successfully to map ice thickness water depth in lakes bedrock depth soil stratigraphy and water table depth it is also used to delineate rock fabric detect voids and identify karst features the effective application of the radar for the high resolution definition of soil stratigraphy and fractures in bedrock is highlighted the basic principles and practices involved in acquiring high quality radar data in the field are illustrated by selected case histories one example demonstrates how radar has been used to map the bedrock and delineate soil horizons to a depth of more than 20 m two case histories show how radar has been used to map fractures and changes of rock type to 40 m range from inside a mine another case history demonstrates how radar has also been used to detect and map the extent of groundwater contamination the corroboration of the radar results by borehole investigations demonstrates the power and utility of the high resolution radar method as an aid for interpolation and extrapolation of the information obtained with conventional coring programmes with the advent of new instrumentation and field procedures the routine application of the radar method is becoming economically viable and the method will see expanded use in the future

authigenic smectite on diatom frustules in bolivian saline lakes abstract observation under the electron microscope of diatom frustules from bolivian altiplano saline lakes shows that many of these are coated with particles occurring as tiny sheets the frustules can be found to be almost completely replaced by these sheets isolated sheet aggregates seem to have resulted from completely transformed frustules section observations of altered frustules bear out that the sheets have grown from biogenic silica through replacement selected area diffraction dark field observation microdiffraction and elemental microanalysis show that the particles on the diatom frustules consist of a poorly crystallized mg smectite the unambiguous localisation of this authigenesis allows us to reconstruct its hydrochemical and sedimentological environment observation of the most recent lake sediments has pointed out that at least two main conditions are required for this authigenesis at 5 c saturation with respect to amorphous silica and a ph above 8 2 variations in the mg concentration have no significant effect

space time correlations of seismotectonic parameters examples from japan and from turkey preceding the izmit earthquake analysis of the correlation between fractal attributes of complex seis motectonic variables may offer insights into seismic hazard assessment the guten berg richter moment magnitude and moment source area relations yield a direct fractal relationship among the gutenberg richter b value occurrence rate and the characteristic linear dimension of the fault plane square root of fault surface area in contrast temporal variation in the correlation dimension of epicenters dc i s found in several studies to correlate negatively with the b value in different regions of the world spatial variations between the b value and dc also tend to oppose each other in japan negative correlations are also observed in the regional scale com parisons of the capacity dimension do of active fault systems and the b value however at local scales the relationship yields both positive and negative correla tion the occurrence of positive or negative correlation appears to be controlled by different modes of failure within the active fault complex spatial variations between the b value and dc along the northern anatolian fault zone nafz suggest that on average from 1900 to 1992 earthquake magnitudes were higher and epicenters more scattered within the central nafz than in its eastern and western segments temporal analysis reveals that the relationship between the b value and dc are nonstationary temporal correlations are generally negative a period of positive correlation is observed between 1976 and 1988 during the last 3 yr of this period 1985 1988 both the b value and d c rose significantly suggesting that stress release occurs through increased levels of low magnitude and increasingly scattered seismicity this dispersed pattern of seismicity in combination with higher slip rates in the central nafz may be one that did not adequately relieve stress along the main fault zone this change in behavior and the tendency during the last century for the seismicity to migrate westward along the nafz may point to an increased risk of larger magnitude events such as the i zmit earthquake

the accommodation of large strains in the upper lithosphere of the earth and other solids by self similar fault systems the geometrical origin of b value plate tectonics has provided a method of visualizing the geometry of the deformation of the earth s lithosphere on a large scale the description is so concise that for many purposes it provides an explanation of geological processes that overshadows the need to understand the driving processes the mechanics of the zones between the plates are less well understood particularly in continental regions where large areas are subject to deformation both continuous and discontinuous models have been tried but both have obvious drawbacks

fractal interrelationships between topography and structure fractal interrelationships between topography and structure are investigated in two areas of the north american central appalachian mountains one in the intensely deformed valley and ridge province and the other in the relatively undeformed foreland area of the appalachian plateau province in the valley and ridge province the fractal dimensions of topographic and structural relief vary systematically along the strike of major folds following a second order polynominal trend cross correlation of the fractal dimensions of topography to structure indicates that there is a significant positive correlation between the two fractal analysis of topography in the relatively undeformed foreland area of the appalachian plateau revealed no significant variation in the fractal characteristics of topography across the study area consistent with the lack of near surface structure however fractal analysis of deeper structures beneath the plateau area undertaken using reflection seismic data revealed step wise increases in fractal dimension from the deeply buried precambrian basement to the near surface these vertical changes in fractal dimension can be related to the tectonic history of the area taken together these studies indicate that fractal analysis provides a means to quantify and compare the influence of near surface structure on topographic development and lateral and vertical structural variability fractal analysis provides a means to characterize the systematic changes in the complex patterns formed by topography and structure and the interrelationships between them similarity in their fractal characteristics implies similarity in the relative amplitude and abundance of different wavelength features in the topographic or structural profile 1998 john wiley sons ltd

rates of aftershock decay and the fractal structure of active fault systems abstract aftershock activity on frequency decay against time is characterized by a power law the modified omori formula of an exponent p which differs with each aftershock sequence a theoretical study suggested that p which is a rate constant of aftershock decay is related to the fractal dimension of a pre existing fault system this has however never been checked aftershock activity on size distribution is also characterized by an exponential distribution against magnitude the gutenberg richter relation with a slope b although p is expected to be related to b which is related to the partitioning rate of earthquake energy the relationship has never been established here the relation between the p values and the fractal dimensions of the pre existing fault systems and that between the p values and the b values are explored using natural seismicity data and data of the observable fault systems the p and b values were estimated for fifteen aftershock sequences which occurred in japan in this paper aftershocks were identified on the basis of a phenomenological definition in the seismicity data the fractal capacity dimensions d0 are estimated for the pre existing active fault systems observed on the surface in the aftershock regions in the present paper the standard box counting method was adopted to get the d0 negative correlations between 1 p and d0 and 2 p and b were observed with some scattering observation 1 shows that the rate of aftershock decay p decreases systematically with increasing occupancy rate of the pre existing active fault system d0 and suggests that aftershock decay dynamics is constrained by the pre existing fracture field observation 2 shows that p certainly has a relation with b moreover we offer possible interpretation on these negative correlations and some scatters in both observations the scatters are interpreted as the scatter of the difference of two fractal dimensions between 3 d fracture construction in the crust and 2 d cross sectional surface observed active fault system supported by further tests this paper strongly suggests that the scaling for a natural fracture system is self affine with different fractal scalings in different directions rather than self similar which would be a manifestation of regional anisotropy of the fracture system and that the seismic parameters p and b depend on the 3 d construction of the fracture system in the crust

holocene hydrologic variation at lake titicaca bolivia peru and its relationship to north atlantic climate variation a growing number of sites in the northern hemisphere show centennial to millennial scale climate variation that has been correlated with change in solar variability or with change in north atlantic circulation however it is unclear how or whether these oscillations in the climate system are manifest in the southern hemisphere because of a lack of sites with suitably high sampling resolution in this paper we reconstruct the lake level history of lake titicaca using the carbon isotopic content of sedimentary organic matter to evaluate centennial to millennial scale precipitation variation and its phasing relative to sites in the northern hemisphere the pattern and timing of lake level change in lake titicaca is similar to the ice rafted debris record of holocene bond events demonstrating a possible coupling between precipitation variation on the altiplano and north atlantic sea surface temperatures ssts the cold periods of the holocene bond events correspond with periods of increased precipitation on the altiplano holocene precipitation variability on the altiplano is anti phased with respect to precipitation in the northern hemisphere monsoon region more generally the tropical andes underwent large changes in precipitation on centennial to millennial timescales during the holocene copyright 2005 john wiley sons ltd

multifractal analysis of earthquakes multifractal properties of the epicenter and hypocenter distribution and also of the energy distribution of earthquakes are studied for california japan and greece the calculateddq q curves the generalized dimension indicate that the earthquake process is multifractal or heterogeneous in the fractal dimension japanese earthquakes are the most heterogeneous and californian earthquakes are the least since the earthquake process is multifractal a single value of the so called fractal dimension is not sufficient to characterize the earthquake process studies of multifractal models of earthquakes are recommended temporal changes of thedq q curve are also obtained for californian and japanese earthquakes thedq q curve shows two distinctly different types in each region the gentle type and the steep type the steeptype corresponds to a strongly heterogeneous multifractal which appears during seismically active periods when large earthquakes occur dq for smallq or negativeq is considerably more sensitive to the change in fractal structure of earthquakes thandq forq 2 we recommend use ofdq at smallq to detect the seismicity change in a local area

introduction to special section on physical processes in geodynamics on may 16 and 17 1992 a meeting was held at cornell university as part of activities to honor donald l turcotte on the occasion of his 60th birthday which actually occurred on april 22 1992 the papers in the following special section are a result of that meeting which included invited presentations and posters representing the diverse areas of geology and geophysics to which donald turcotte has contributed three of the papers deal with aspects of mantle convection a c fowler addresses the problem of initiation of subduction by extending boundary layer theory to a viscoplastic rheology turcotte and oxburgh 1967 pioneered such studies by showing how boundary layer theory could be used to describe the dependence of geophysical observables such as heat flux on distance from a midocean ridge or age of the oceanic crust d w sparks et al use a model of three dimensional convection beneath a segmented ridge to explore how buoyancy effects and melt production beneath a spreading center influence ridge parallel variations in crustal thickness and gravity magma migration and the dynamics of midocean ridges have been major focuses of donald turcotte s research in papers dating back to 1978 e g turcotte and ahern 1978 ahern and turcotte 1979 turcotte 1982a kenyon and turcotte 1987 g a glatzmaier and g schubert calculate models of three dimensional two layer mantle convection in a spherical shell and compare with whole layer spherical shell three dimensional convection models these models represent the end member states of a spectrum of possible modes of mantle convection turcotte and oxburgh 1972 oxburgh and turcotte 1978 turcotte 1979a silver et al 1988

a tsunami ca 6300 years bp and other holocene environmental changes northern hawke s bay new zealand abstract sediment cores collected in a coastal lagoon a few kilometres east of wairoa northern hawke s bay new zealand were examined using sedimentological geochemical palynological and micropaleontological analyses a distinct short lived catastrophic saltwater inundation csi about 6300 years bp and possibly other minor marine incursions are preserved in the coastal estuarine to lagoonal freshwater sedimentary sequences which have been deposited in the last 6500 years the csi is characterised by a gravel unit that thins landward and decreases in particle size to sand within a sequence consisting mainly of brackish estuarine muds diatom assemblages indicate a marked change from the shallow brackish estuarine muds to marine gravels and sands to brackish estuarine muds the marine influence in the gravel and sand is also shown by the presence of marine dinoflagellates and a peak in na rb sedimentological chemical and paleontological in particular diatoms evidence indicates it is a csi we conclude that this was a tsunami and propose the most likely propagating mechanisms marine influence decreases upcore and totally freshwater conditions are evident in the upper section of the cores the geochemistry of the sediments mainly reflects the change in stratigraphy with distinct signatures for tephra na fe cr organic rich and peat units as br and the coarse gravel sand csi unit na rb cr fe but it is also indicative of changes in depositional environment the change in chemistry na rb in the csi event is indicative of a saltwater influence whereas a marked change in s content suggests a sudden change from brackish to freshwater conditions shortly after 4800 years bp another peak in s and br content about 3200 years bp may indicate another temporary change to brackish conditions

the role of an intracrustal asthenosphere on the behavior of major strike slip faults measurements of strain accumulation adjacent to the san andreas fault indicate that the zone of strain accumulation extends only a few tens of kilometers away from the fault such a narrow zone of cyclic strain accumulation and release is consistent with the measured coseismic strain and inferred stress drop during the 1906 earthquake the restricted zone of cyclic accumulation and release of elastic energy adjacent to major strike slip faults has been attributed to the damping effect of a viscoelastic asthenosphere however to explain the narrowness of the zone on the san andreas fault it is necessary to conclude that the thickness of the lithosphere is 10 20 km this does not appear to be consistent with the relatively low surface heat flow measurements in this paper an alternative four layer model is proposed to explain the behavior of the san andreas fault an upper elastic plate extends to a depth of about 15 km the depth of the deepest seismicity on and adjacent to the fault beneath this upper elastic plate is a soft intracrustal asthenosphere that exhibits a viscoelastic behavior the viscous behavior of these crustal rocks at relatively low temperatures is attributed to either the presence of quartz which is known to have a very soft rheology or the presence of water that can lead to pressure solution creep or to both effects beneath this soft layer is a second elastic layer made up of the tough lower crustal and upper mantle rocks and beneath this second elastic layer is the asthenosphere there is extensive geological and geophysical evidence for the existence of an intracrustal asthenosphere both in california and elsewhere we show that the damping due to the intracrustal asthenosphere can explain the observed narrow zone of cyclic strain accumulation and release on the san andreas fault

towards a new view of earthquake phenomena recent advances in the theory of fracture and fragmentation are reviewed empirical laws in seismology are interpreted from a fractal perspective and earthquakes are viewed as a self organized critical phenomenon soc earthquakes occur as an energy dissipation process in the earth s crust to which the tectonic energy is continuously input the crust self organizes into the critical state and the temporal and spatial fractal structure emerges naturally power law relations known in seismology are the expression of the critical state of the crust an soc model for earthquakes which explains the gutenberg richter relation the omori s formula of aftershocks and the fractal distribution of hypocenters is presented a new view of earthquake phenomena shares a common standpoint with other disciplines to study natural complex phenomena with a unified theory

fault friction regional stress and crust mantle coupling in southern california from finite element models ongoing deformation of southern california is simulated in a set of 63 models in an attempt to empirically determine fault friction to a previous code for simulation of anelastic crustal strain we introduce a new finite element to represent a curved fault of arbitrary rheology we also add several selfconsistent patterns of horizontal drag on the base of the crust caused by independent upper mantle flow a grid of isoparametric finite elements represents the regional fault geometry and the known variations in elevation and heat flow plate tectonic velocity boundary conditions are applied solutions include the time averaged flow velocities and fault slip rates and vertically averaged stresses each model is scored by comparing its slip rate predictions with 56 rates from dated offset geologic features in membrane stress models the optimal fault friction is 0 4 0 6 frictional self heating of faults is not a major factor determining strength addition of crust mantle coupling improves results if convergence of north american and pacific lithospheres is assumed to occur under the transverse ranges among such models those with fault friction of about 0 3 score best by most norms of the prediction error these have over 80 of regional strain in faults and only a small amount of block deformation however one model with friction of 0 85 scores better by the percent of correct predictions norm this model has only half the regional strain as fault slip and matches slow rates well but underpredicts slip rates over 1 cm yr furthermore its predictions are degraded considerably if hydraulic lubrication of thrust faults is assumed the low friction models are unaffected we conclude that some source of variation in fault friction remains unmodeled but that at least the fastslipping faults in california have low friction similar to that of hydrated clay gouges appendix is available with entire article on microfiche order from american geophysical union 2000 florida avenue n w washington dc 20009 document b84 001 2 50 payment must accompany order

diatom biostratigraphy of tsunami deposits examples from the 1998 papua new guinea tsunami abstract distinctive diatom assemblages may be associated with tsunami sediments and may often contrast with the assemblages found within sediments underlying the tsunami deposit as well as those associated with the modern coastal environment sediments associated with the 1998 tsunami that destroyed much of the sissano lagoon area in northern papua new guinea have been investigated surface sediments from three transects across the sediment spit near warapu have been examined for diatom content and preservation the preservation is variable and the data show an often chaotic assemblage that can be attributed to the tsunami waves incorporating and depositing diatoms from distinctive habitat zones during their runup and subsequent backwash the diatoms identified within the warapu sediments indicate an origin from within the inter tidal and offshore area rather than from the beach sand spit complex the sand deposits disclose a high percentage in excess of 75 of broken diatom valves and a predominance of centric circular species due to preferential preservation the study demonstrates that the application of diatom biostratigraphy to modern tsunami deposits can be used in conjunction with other stratigraphical lines of evidence to interpret the source and provenance of historical and palaeo tsunami deposits