bluuebunny/crossref_metadata_2025_split huggingface dataset:
Earthquakes, Geology and Crustal Features in Southern New England
Authors: Kafka Alan L. 
Published: July 2019

Abstract
Within southern New england (SNE) and adjacent areas lies a variety of tectonic regions extending from the ancient North American craton to the Avalonian Terrane. This region, which is part of the northern Appalachians, has had a moderate level of seismic activity throughout its recorded history. Although the geology and geophysics of SNE have been studied extensively, it has been difficult to correlate the seismic activity in this region with geologic structures mapped on the earth’s surface.
The distribution of earthquakes located by regional seismic networks in SNE generally resembles that of historical earthquakes in this region. In both the network and historical records, a cluster of earthquakes occurs near Moodus, CT and more diffuse seismicity occurs in the eastern coastal regions. Both data sets show earthquake activity in the vicinity of the 1755 earthquake that occurred on the coast of Cape Ann, MA, as well as seismicity near the boundary between southwestern CT and NY State. Aside from these very general similarities, the location uncertainties of the historical earthquakes make it difficult to compare the two records of seismicity in any greater detail.
Information about the lateral variation of seismic velocities in the shallow crust beneath SNE has been obtained from studies of dispersion of short-period, fundamental-mode Rayleigh waves (Rg). Rg waves with periods between about 0.2 and 2.5 sec have been studied, and dispersive properties of Rg in that period range are sensitive to lateral variation in the upper few kilometers of the crust. Based on Rg dispersion studies, it appears that SNE can be divided into regions of distinct shallow crustal structure. The pattern of lateral variation is Rg dispersion is similar to the pattern of teleseismic residuals and gravity anomalies, suggesting that the lateral variation revealed by the Rg studies extends deeper into the crust. These results, however, do not reveal any obvious correlations between crustal features and seismicity.
New Focal Mechanisms for the New England Region: Constrains on the Regional Stress Regime
Authors: Ebel John E. , Bouck Bruce R. 
Published: July 2019

Abstract
Single-event focal mechanisms for fifteen earthquakes in New England and New York have been determined. Thirteen of these are new focal mechanisms, while two are redeterminations for events with previously reported solutions. The focal mechanisms display considerable scatter in P-axis orientation, as has been reported in earlier studies. Some areas within the region, such as central New Hampshire and northeastern Massachusetts, show locally consistent principal stress directions. Other areas, such as central Maine, do not. All but one or two of the new focal mechanisms have P-axis and T-axis orientations which fall within the range of values calculated by Gephart and Forsyth (1985) for a regional stress field of horizontal, E-W maximum stress and vertical minimum stress in New England.
Seismogenesis in Eastern Canada
Authors: Hasegawa H. S. 
Published: July 2019

Abstract
The pattern of seismicity in eastern Canada depends on the presence of weak zones from previous major tectonic orogenies and how these weak zones are reactivated by local and regional stress fields and geophysical processes. Within the Canadian Shield, away from seismotectonic trends, there is a low level of seismicity and earthquakes tend to be small, less than M5. However, along seismically active trends, earthquakes as large as M7 have occurred. The seismotectonic features fall into four main categories: positive (uplift) continental basement linears; grabens formed by old plate separation; passive rifted margins offshore; and extinct spreading ridges. Two of the positive seismotectonic trends are the Boothia Uplift-Bell Arch that transects the northeastern part of the craton and northeastern Baffin Island, where the effects of postglacial rebound on the upper crustal stress field are the most pronounced. The St. Lawrence Valley (and interconnecting grabens) is a seismically active graben system that contains the most seismically active region (the Charlevoix zone) in eastern Canada. The extinct spreading ridge along the Labrador Sea and the Mesozoic rifted margin along Baffin Bay and Labrador Sea contain clusters of moderate seismicity. There are diffuse zones of moderate seismicity over some geological provinces (e.g. Central Metasedimentary Belt in western Quebec) apart from major tectonic features, a confined seismic zone (within an intrusion) in the Miramichi region and seismicity at the intersection of faults in northern Ontario. In the Nahanni region, which is situated near the boundary between the northeast Cordillera and the Interior Platform, the commencement of a noteworthy earthquake sequence with magnitude up to Ms 6.9 indicates considerable stress-strain build-up over a large area. There is an anticline in the epicentral area that is bounded by thrust faults and mountain ranges.
In order to enhance our understanding of causative factors of current seismicity, it is necessary to determine in greater detail the tectonic forces and geophysical processes that are reactivating pre-weakened faults along the seismotectonic trends and over broad, diffuse seismogenic regions. Some of these factors are the rate of stress build-up, stress concentration at the intersection of faults and between mountain ranges, residual stress, the role of pore fluids, individual block movement, whether this movement is due to postglacial rebound or to other underlying viscoelastic phenomena and the rate of sediment deposition along the continental slope. Paleoseismicity is useful not only for the reconstruction of old large earthquakes but also for providing insight as to why surface fault offsets have not been observed in regions where large earthquakes (and associated high rate of microseisrnicity) have occurred within the past several hundred years.
Disintegration, Faulting and Seismogenesis of the North China Craton
Authors: Guoyu Ding 
Published: July 2019

Abstract
The North China Craton (NCC) began to disintegrate completely in the Yanshan Movement period (Jurassic-Cretaceous) forming a great number of NE, NEN, NW and WNW trending faults. Such fault systems have played an important role in the development of tectonics and seismicity in the Craton area. There has been a big change of stress field since the Pliocene, from predominantly normal faulting to predominantly strike-slip faulting. The NCC is an area with high seismicity. The recent seismicity is obviously controlled by the tectonic framework derived from Craton disintegration. Six strong earthquakes with M > 8.0 in this area have occurred in the past two thousand years. Many strong earthquakes in the NCC area are mainly caused by preexisting faults that move horizontally forming pull-apart basins.
The Intersection Model for Intraplate Earthquakes
Authors: Talwani Pradeep 
Published: July 2019

Abstract
The tectonic cause of intraplate earthquakes has remained enigmatic. As newer data became available, several common features were apparent for intraplate earthquakes occurring in a wide variety of geologic terranes. These have been incorporated in the intersection model. Seismicity occurs near the intersection of, and by the reactivation of, preexisting zones of weakness. The intersections are the foci of anomalous stress build up in response to the ambient stress field due to plate tectonic forces. This anomalous stress buildup is relieved by strike slip motion on a suitably oriented fault and, due to kinematic adjustment, is followed by vertical or horizontal movement on the intersecting fault. The intersection model has several elements that complement other models proposed to explain intraplate earthquakes.
Geodetic Evidence for Tectonic Deformation in the Eastern United States
Authors: Reilinger Robert 
Published: July 2019

Abstract
The historic geodetic data base in the eastern United States dates back over 100 years. Although instrumentation and hence measurement precision has improved since the initial observations, the basic techniques [leveling, triangulation, water level gauging] remained unchanged until the recent introduction of space geodesy [Very Long Baseline Interferometry (VLBI), Satellite Laser Ranging (SLR), Global Positioning System (GPS)]. Because of this, it has been possible to compare repeated observations to identify apparent changes in relative positions. Such “changes” can reflect observational errors, non-tectonic movements (water level effects, monument instability, loading, etc.) or tectonic/isostatic deformation.
A number of possible deformation features in the eastern U. S. have been reported in the literature, including uplift of the southern Appalachian and Adirondack mountains, doming of the Gulf coast inland of the Mississippi delta, subsidence of Chesapeak Bay and along the coast of Maine, horizontal deformation in New York and Connecticut, and possible fault related deformation near Charleston and in the New Madrid area. Unfortunately, it is not dear to what extent any of these features represent tectonic deformations and hence what their significance may be for the earthquake problem.
An important recent development in monitoring regional deformation has been the establishment of the eastern U. S. GPS strain network by the National Geodetic Survey. The network consists of roughly 45 sites uniformly distributed east of the Rocky Mountains. The network was established in 1987 and will be reobserved in 1989. Subsequent reobservations will be made at 2 to 5 year intervals depending on analysis of the early measurements. Given the precision of the GPS measurements (few cm in 3-D relative positions), a considerable time period will be required to detect the subtle deformations expected for this intraplate region.
Perhaps more immediate information will result from recent progress in recognizing and correcting systematic errors in the historic geodetic data base. This, together with the newly automated historic data base, and improved techniques for integrating and analyzing these extensive observations, provide the necessary basis for effectively evaluating the deformational features listed above. Given the potential importance of these data for understanding tectonic processes (and the huge expense of collecting these measurements over the pst century), such studies should be an integral part of future earthquake studies in the eastern U. S.
Source Parameters of Large Australian Intracontinental Earthquakes
Authors: McCaffrey Robert , Fredrich Joanne 
Published: July 2019

Abstract
We have examined the largest earthquakes in the Australian continent over the past 20 years by modeling their teleseismic long-period P and SH and short-period P waveforms. Eight earthquakes beneath the continent show thrust faulting at depths shallower than 10 km. Three (1, 2, 4 below) produced surface faulting and their waveforms indicate centroid depths of 3 km or less. The P-axes in the southwestern half of the continent have easterly trends. Preliminary examination of the 3 large earthquakes near Tennant Creek on 22 January, 1988, (7–9) indicate thrusting at less than 10 km depth, but with N-trending P-axes. The largest event (9), at 12:06 GMT, had a seismic moment of roughly 1019 Nm, which makes it comparable in size to the 1968 Meckering event (1). One event (6) beneath the continental margin indicates strike-slip at 26 km depth.
Selected Strong and Weak-Motion Data From the Loma Prieta Earthquake Sequence
Authors: Jarpe S. P. , Hutchings L. J. , Hauk T. F. , Shakal A. F. 
Published: July 2019

Abstract
The purpose of this paper is to document the strong- and weak-motion seismic data from the Loma Prieta earthquake and its aftershocks obtained by Lawrence Livermore National Laboratory (LLNL), and to present some analysis of the spectral seismic response using both weak- and strong-motion recordings. LLNL operates six free-field, digitally recorded, triaxial, strongmotion accelerographs in the vicinity of LLNL; five of these were operating during the Loma Prieta earthquake. Two days after the main event, LLNL initiated a field deployment of 3-component weak-motion instruments to record aftershocks at three LLNL sites and four California Strong Motion Instrumentation Program (CSMIP) sites that recorded strong-motion from the main event.
Spectral ratios of strong- and weak-motion recordings are computed for two pairs of rock and soil sites. One pair of stations is in the vicinity of LLNL, and the other pair is Treasure Island TRI (fill) and Yerba Buena Island YBI (rock) in San Francisco Bay near the Bay Bridge. For the first pair, the weak-motion spectral ratios predict the strong-motion amplification, within 95% confidence limits, for frequencies from 3 to 12 Hz. For TRI and YBI, the strong-motion spectral ratio is much lower than the weak-motion 95% confidence region for frequencies from 1 to 7 Hz. The strong-motion ratio, however, still suggests that the soil underlying TRI resulted in a factor of 3 amplification of energy between 1 and 4 Hz. This is in contrast to the factor of 8 amplification of the weak-motion energy, derived from the spectral ratios of 7 Loma Prieta aftershocks. The large difference between the weak-motion and strong-motion spectral ratios reinforces the limitation that weak-motion cannot be used to directly predict strong-motion amplification at sites underlain by soils that may respond non-linearly at high strain levels.
A further examination of weak-motion recordings indicates that the source effect can be removed and the propagation path effects approximated so that the site response can be isolated. Resulting site specific spectral amplifications reveal that the spectral ratio method can lead to erroneous conclusions if the “rock” site has a complicated geology. At two sites near LLNL the apparent diminishing of spectral amplitudes below 5 Hz observed in the spectral ratios was actually due to amplification of spectral response at the rock site. It appears that the reference site spectral ratios at low frequencies may have been influenced by topography or near-surface geologic features. For the other pair of sites, the spectrum at YBI, the rock site, was flat, so that the features in the spectral ratios are due to the seismic response of the soil at TRI.
A Comparison of the 1981, 1982, 1986 and 1987–1988 Microearthquake Swarms At Moodus, Connecticut
Authors: Ebel John E. 
Published: July 2019

Abstract
Four extensive microearthquake swarms, in 1981, 1982, 1986 and 1987–1988, have occurred near Moodus, Connecticut since the installation of a dense local monitoring network in 1979. All of the swarms have been accompanied by at least one event of M≥2.0, have had depths of less than 2.4 km, and have originated from one small primary source volume. A few of the events from 1981 and 1982 were located about 1.5 km west to southwest of this primary source locality. The time histories and energy releases have varied from swarm to swarm, with the 1981 and 1982 swarms having some foreshocks, a main shock, and a decaying aftershock pattern. The 1986 and 1987–1988 swarms were more distributed in time and totaled fewer events than the earlier swarms. The b-value for the 1987–1988 swarm is closer to that of the foreshocks from 1981 and 1982 than that of the aftershocks from those swarms. The 1980’s have been an unusually active period at Moodus, but the geologic and seismological evidence are ambiguous as to the cause the Moodus earthquakes and how large an event can take place at this locality.
The January 4, 1989, Earthquake in Bluffton, South Carolina, and its Tectonic Implications
Authors: Talwani P. , Rajendran K. 
Published: July 2019

Abstract
An earthquake of magnitude 2.8 occurred on January 4, 1989, at 9:39:01.47 UTC (4:39 am EST) near Bluffton, in the lower South Carolina Coastal Plain, a region of low seismicity. More than seventy people in the Bluffton-Hilton Head area reported either hearing or feeling this early morning event. Historically, there have been three earthquakes, two of which had a MMI ≥ V, near Savannah, 25 km southwest of this earthquake. Recent discoveries of earthquake induced liquefaction features in the Bluffton area suggested that this area had been subjected to large ground motion in the past. Together, these data lead to the preliminary inference of a possible seismic source zone near Bluffton.
The Woodstock Lineament: A Possible Surface Expression of the Seismogenic Fault of the 1886 Charleston, South Carolina, Earthquake
Authors: Marple Ronald T. , Talwani Pradeep 
Published: July 2019

Abstract
A SPOT satellite image of the Charleston, South Carolina, area revealed a linear feature, the Woodstock lineament, that may be the surface expression of a seismogenic fault of the 1886 Charleston earthquake. An enhancement of the SPOT image reveals a linear, 5 km wide band on the east side of the lineament that extends at least 65 km in a north-northeast direction and coincides with a part of the axis of the highest intensity isoseismal contours of the Charleston earthquake. Corroborative geologic, geodetic, and geophysical data suggest that the lineament and associated band may be the result of ongoing tectonic activity on the Woodstock fault inferred from seismicity.
Overview of Research in The New Madrid Seismic Zone
Authors: Johnston Arch C. , Shedlock Kaye M. 
Published: July 2019

Abstract
We review the development of understanding of the seismicity and tectonic structure of the New Madrid seismic zone and the upper Mississippi embayment. The broad framework of a failed intracontinental rift with reactivated seismogenic faults was not established until the mid-1970s. By the early 1990s a much more detailed knowledge of the rift and the current seismicity has been gained but fundamental questions remain. The 25 papers of this Special Issue of Seismological Research Letters convey the location of the most recent research front in such diverse fields as seismology, paleoseismology, seismic and potential-field investigation of rift structure, neotectonic deformation, and seismic hazard estimation and response. The new information content of these papers, considered ensemble, is enormous and highlights the tremendous progress made since the 1970s. These current studies, in turn, sharpen the focus on remaining outstanding problems of seismogenesis in the New Madrid seismic zone. We close with a discussion of what we believe will be the important foci of research in the 1990s.
Liquefaction Evidence for Strong Holocene Earthquake(S) in the Wabash Valley of Indiana-Illinois
Authors: Obermeier S.F. , Munson P.J. , Munson C.A. , Martin J.R. , Frankel A.D. , Youd T.L. , Pond E.C. 
Published: July 2019

Abstract
We have discovered hundreds of planar, nearly vertical sand- and gravel-filled dikes that we interpret to have been caused by earthquake-induced liquefaction in the Wabash Valley of Indiana- Illinois. These dikes range in width from a few cm to as much as 2.5 m. The largest dikes are centered about the general area of Vincennes, Indiana; they decrease in size and abundance to the north and south of this area. Preliminary studies indicate the high possibility that many, if not all, of the dikes were formed by a single large earthquake that took place in the Vincennes area sometime between 2,500 and 7,500 years ago. The severity of ground shaking required to have formed the dikes far exceeds the strongest level of shaking of any earthquake in the central United States since the 1811–12 New Madrid earthquakes.
Distribution and Dating of Prehistoric Earthquake Liquefaction in the Wabash Valley of the Central U.S.
Authors: Munson Patrick J. , Munson Cheryl Ann , Bleuer Ned K. , Labitzke Michael D. 
Published: July 2019

Abstract
Earthquake-induced paleoliquefaction features are exposed in eroding river banks at 24 sites in the lower and central Wabash Valley. North-south distribution of features is at least 165 km. Sites with very large dikes (60–250 cm wide) suggestive of lateral spreads are found near the center of the distribution and extend over an area about 35 km in diameter. Stratigraphy, sedimentology, pedology, and archaeological associations suggest that all liquefaction resulted from a single, large, middle Holocene earthquake with an epicenter in the vicinity of Vincennes, Indiana.
On the Search for Paleoliquefaction in the New Madrid Seismic Zone
Authors: Wesnousky Steven G. , Leffler Lisa M. 
Published: July 2019

Abstract
The great 1811–12 New Madrid earthquakes produced extensive liquefaction in the meisoseismal zone, which is largely within the St. Francis drainage basin of Missouri and Arkansas. We examined 10’s of kilometers of ditch banks within the meisoseismal zone for evidence of prehistoric liquefaction events. Radiocarbon dates indicate that the exposures studied provide a record of the last 5,000 to 10,000 years. Our search has revealed no evidence of widespread paleoliquefaction events and, hence, provides no independent support for the relatively short 550 to 1100 year return time of 1811–12 type earthquakes implied by analyses of the statistics of historical seismicity.
Analysis of the Seismic Origin of a Landslide in the New Madrid Seismic Zone
Authors: Jibson Randall W. , Keefer David K. 
Published: July 2019

Abstract
The New Madrid earthquakes of 1811–12 reportedly triggered many landslides from the bluffs east of the Mississippi River. We use static and dynamic slope stability analyses to determine if landslides currently visible in this area were triggered by seismic shaking or if failure could have occurred in aseismic conditions. We apply this approach to a translational block slide representative of a group of old landslides that previous investigations showed probably were triggered in 1811–12. Slope-stability modeling of aseismic conditions shows that the slide could not have formed aseismically even in unrealistically high ground-water conditions. Dynamic stability analysis using Newmark’s method shows that the landslide would have experienced large displacements – sufficient to cause catastrophic failure – during earthquake shaking similar to that which occurred in 1811–12.
A Review of Time-Frequency Analysis Techniques for Estimation of Group Velocities
Authors: Kocaoglu Argun H. , Long Leland T. 
Published: July 2019

Abstract
Time-frequency analysis techniques, including the classical use of zero crossings to measure period, have been widely used in seismology for the estimation of surface wave group velocities. Group velocity estimation by the short-time Fourier transform and the multiple filter techniques are equivalent. Although these techniques are used most often, their resolution is limited. The resolution is controlled by the window length in the short time Fourier transform and the filter band width in the multiple filter technique. The moving-window autoregressive spectral estimation provides the highest resolution with the shortest possible window length by predicting the properties of the signal outside the analysis window; however, high resolution is obtained at the expense of uncertainty in the amplitude. Recently, the Wigner distribution has been introduced as a tool for mapping dispersed surface waves into the time-frequency domain. Resolution of the Wigner distribution is comparable to that of the moving-window autoregressive spectral estimation. When the spectral density at a given time contains two or more dominant frequencies, their interference causes the Wigner distribution to introduce spurious spectral peaks complicating the interpretation. The Choi-Williams distribution, in which these interference effects are minimized, can be used for such dispersed signals. However, the implementation is computationally complex and the distribution offers only a medium resolution.