Identifying Direct SP-Converted Waves Constrains Local Induced Earthquake Depths

2021 ◽  
Author(s):  
Keith A. Nolte ◽  
George P. Tsoflias
Keyword(s):  
Intermediate Phase ◽  
Sedimentary Rocks ◽  
S Phase ◽  
P Wave ◽  
Earthquake Catalog ◽  
Induced Earthquakes ◽  
Induced Earthquake ◽  
The Past ◽  
Shallow Earthquakes ◽  
Converted Phases

Abstract Seismicity in southern Kansas and northern Oklahoma in the past decade has been associated with fluid injections. In southcentral Kansas, the Wellington earthquake catalog is primarily composed of local, low-magnitude events. Approximately 22% of recorded earthquakes over a 2.5 yr period exhibit a seismic phase arriving between the direct P phase and direct S phase with particle motion similar to the P wave. This intermediate phase was identified as an S to P conversion (SP phase) occurring in the sedimentary rocks instead of the hypothesized basement to sedimentary section transition. We exploit the SP-converted phases to improve the depth accuracy of shallow earthquakes and to constrain VP/VS. The revised depth calculations further confirm that these local induced earthquakes are occurring in the shallow crystalline basement, below the sedimentary section in which fluids are injected.

scholarly journals S-wave experiments for the exploration of a deep geothermal carbonate reservoir in the German Molasse Basin

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Britta Wawerzinek ◽  
Hermann Buness ◽  
Hartwig von Hartmann ◽  
David C. Tanner
Keyword(s):  
Upper Jurassic ◽  
Carbonate Reservoir ◽  
P Wave ◽  
Seismic Survey ◽  
Seismic Exploration ◽  
Molasse Basin ◽  
S Wave ◽  
Induced Earthquakes ◽  
Conversion Point ◽  
Facies Classification

AbstractThere are many successful geothermal projects that exploit the Upper Jurassic aquifer at 2–3 km depth in the German Molasse Basin. However, up to now, only P-wave seismic exploration has been carried out. In an experiment in the Greater Munich area, we recorded S-waves that were generated by the conventional P-wave seismic survey, using 3C receivers. From this, we built a 3D volume of P- to S-converted (PS) waves using the asymptotic conversion point approach. By combining the P-volume and the resulting PS-seismic volume, we were able to derive the spatial distribution of the vp/vs ratio of both the Molasse overburden and the Upper Jurassic reservoir. We found that the vp/vs ratios for the Molasse units range from 2.0 to 2.3 with a median of 2.15, which is much higher than previously assumed. This raises the depth of hypocenters of induced earthquakes in surrounding geothermal wells. The vp/vs ratios found in the Upper Jurassic vary laterally between 1.5 and 2.2. Since no boreholes are available for verification, we test our results against an independently derived facies classification of the conventional 3D seismic volume and found it correlates well. Furthermore, we see that low vp/vs ratios correlate with high vp and vs velocities. We interpret the latter as dolomitized rocks, which are connected with enhanced permeability in the reservoir. We conclude that 3C registration of conventional P-wave surveys is worthwhile.

scholarly journals Vestige of The Ancient Estuarine of Cisaar Valley, Sumedang as One of the Pleistocene Fossil Bearing Site in West Jawa

2019 ◽  
Vol 8 (2) ◽  
pp. 65-80
Author(s):  
Unggul Prasetyo Wibowo ◽  
Anton Ferdianto ◽  
Nurul Laili ◽  
Dida Yurnaldi ◽  
Ruli Setiawan
Keyword(s):  
Depositional Environment ◽  
Sedimentary Rocks ◽  
Estuarine Environment ◽  
Shallow Marine ◽  
East Part ◽  
The Past ◽  
Braided Channel ◽  
Freshwater Mollusk ◽  
Past Data

Cisaar Valley is located on the east part of Sumedang Regency, West Jawa Province. It’s close to the boundary of Sumedang-Majalengka Regency. In this location the sandy and clay dominated sedimentary rocks are well exposed along the outcrops in the Cisaar Valley. These sedimentary rocks is inferred from Pliocene-Pleistocene deposits from Kaliwangu and Citalang Formation. Foraminifera microfossil that commonly used for interpretation of depositional environment is rarely found, whereas freshwater mollusk and vertebrate fossils often found in the sediment rocks of this area.  This condition raises a question, what is the environment of this valley in the past? Data obtained from measured stratigraphic sections along Cisaar river and its tributary rivers in Cibengkung and Cirendang hamlets, Jembarwangi village. There are at least three depositional paleoenvironments which from old to young are: shallow marine, estuarine and fluviatil braided channel depositional paleoenvironment.  Characteristics of the lower, middle and upper of the estuarine environment were found in this Cisaar Valley as the evidences of the oceanic regression processes was happened in the past in this area. 

P-wave travel times from shallow earthquakes recorded in India and inferred upper mantle structure

1968 ◽  
Vol 58 (6) ◽  
pp. 1879-1897
Author(s):  
K. L. Kaila ◽  
P. R. Reddy ◽  
Hari Narain
Keyword(s):  
Upper Mantle ◽  
P Wave ◽  
Mantle Structure ◽  
Travel Times ◽  
The North ◽  
Shallow Earthquakes ◽  
Upper Mantle Structure ◽  
Wave Travel ◽  
Excess Value ◽  
Velocity Changes

ABSTRACT P-wave travel times of 39 shallow earthquakes and three nuclear explosions with epicenters in the North in Himalayas, Tibet, China and USSR as recorded in Indian observatories have been analyzed statistically by the method of weighting observations. The travel times from Δ = 2° to 50° can be represented by four straight line segments indicating abrupt velocity changes around 19°, 22° and 33° respectively. The P-wave velocity at the top of the mantle has been found to be 8.31 ± 0.02 km/sec. Inferred upper mantle structure reveals three velocity discontinuities in the upper mantle at depths (below the crust) of 380 ± 20, 580 ± 50 and 1000 ± 120 km with velocities below the discontinuities as 9.47 ± 0.06, 10.15 ± 0.07 and 11.40 ± 0.08 km/sec respectively. The J-B residuals up to Δ = 19° are mostly negative varying from 1 to 10 seconds with a dependence on Δ values indicating a different upper mantle velocity in the Himalayan region as compared to that used by Jeffreys-Bullen in their tables (1940). Between 19° to 33° there is a reasonably good agreement between the J-B curve and the observation points. From Δ = 33° to 50° the J-B residuals are mostly positive with an average excess value of about 4 sec.

Complex Shear-Wave Anisotropy from Induced Earthquakes in West Texas

2020 ◽  
Vol 110 (5) ◽  
pp. 2242-2251 ◽  
Author(s):  
Regan Robinson ◽  
Aibing Li ◽  
Alexandros Savvaidis ◽  
Hongru Hu
Keyword(s):  
Shear Wave ◽  
Induced Seismicity ◽  
High Rate ◽  
Normal Faults ◽  
Permian Basin ◽  
Induced Earthquakes ◽  
Large Delay ◽  
Delaware Basin ◽  
West Texas ◽  
Shallow Earthquakes

ABSTRACT We have analyzed shear-wave splitting (SWS) data from local earthquakes in the Permian basin in west Texas to understand crustal stress change and induced seismicity. Two SWS parameters, the fast polarization direction and the delay time, are computed using a semiautomatic algorithm. Most measurements are determined in the Delaware basin and the Snyder area. In both regions, SWS fast directions are mostly consistent with local SHmax at stations that are relatively far from the earthquake clusters. Varying fast directions at one station are related to different ray paths and are probably caused by heterogeneity. In the Snyder area, most northeast–southwest fast directions are from the events in the northern part of the cluster, whereas the northwest–southeast fast directions are mostly from the southern part. The northeast–southwest and northwest–southeast fast directions could be attributed to the northeast-trending normal faults and the northwest-trending strike-slip faults, respectively. SWS results in the Delaware basin have two unique features. First, most shallow earthquakes less than 4 km deep produce relatively large delay times. This observation implies that the upper crust of the Delaware basin is highly fractured, as indicated by the increasing number of induced earthquakes. Second, diverse fast directions are observed at the stations in the high-seismicity region, likely caused by the presence of multiple sets of cracks with different orientations. This situation is possible in the crust with high pore pressure, which is expected in the Delaware basin due to extensive wastewater injection and hydraulic fracturing. We propose that the diversity of SWS fast directions could be a typical phenomenon in regions with a high rate of induced seismicity.

scholarly journals “Palaeoentomology”: A modern journal for a science dealing with the past

2018 ◽  
Vol 1 (1) ◽  
pp. 1 ◽  
Author(s):  
DANY AZAR ◽  
JACEK SZWEDO ◽  
EDMUND JARZEMBOWSKI ◽  
NEAL EVENHUIS ◽  
DIYING HUANG
Keyword(s):  
Sedimentary Rocks ◽  
Fossil Insects ◽  
The Past ◽  
Terrestrial Arthropods ◽  
Invertebrate Paleontology ◽  
Xxist Century ◽  
History Of ◽  
Geological Sciences ◽  
Fossil Resins ◽  
Biological Literature

Palaeoentomology started in the late XVIIIth century, shortly after the 10th edition of Linnaeus’ Systema Naturae (the foundation of modern taxonomy), when papers on the curiosities of insects entombed in fossil resins were published. The beginning of XIXth century (with the growing interest in geological sciences and prehistoric life) witnessed the first attempts to study and describe insects from sedimentary rocks. This discipline then developed during the XIXth and beginning of the XXth centuries; and resulted in some major works and reviews (summarizing the knowledge on fossil insects and other terrestrial arthropods) published in the geological and biological literature. The XXth century was a period of relatively slow but constant development in palaeoentomology, during which the famous “Treatise on invertebrate paleontology: Arthropoda 4. Superclass Hexapoda” (cataloguing the knowledge on fossil insects) was published (Carpenter, 1992). At the beginning of XXIst century, palaeoentomology grew significantly and exponentially; and two major manuals (“History of insects” and “Evolution of the insects”) were published (Rasnitsyn & Quicke, 2002; Grimaldi & Engel, 2005, respectively). These manuals helped to encourage more students and researchers to work on fossil insects and other terrestrial arthropods. 

On rhodonite and tephroite from Treburland manganese mine, Altarnun, Cornwall; and on rhodonite from other localities in Cornwall and Devonshire

1946 ◽  
Vol 27 (194) ◽  
pp. 221-235 ◽  
Author(s):  
Arthur Russell
Keyword(s):  
Sedimentary Rocks ◽  
Point Of View ◽  
Contact Metamorphism ◽  
Geological Survey ◽  
The West ◽  
The Past ◽  
Manganese Deposits ◽  
The Many

Of the many small manganese deposits which have in the past been worked in both Cornwall and Devonshire that of Treburland is from the mineralogical point of view by far the most remarkable, its especial interest being due to the variety of minerals which it has afforded and to the fact that it and one other are the only manganese deposits in the west of England which are known to lie on the contact of igneous and sedimentary rocks and which have consequently been vitally affected by contact metamorphism.The following observations are based on frequent visits to the spot since the year 1906, when I first stumbled across the locality, which, strange to say, has only received very cursory mention by the Geological Survey and has altogether escaped mention in mineralogical literature.

POSSIBLE P‐WAVE OBSERVATIONS IN SHORT‐PERIOD SEISMIC NOISE

Geophysics ◽  
1965 ◽  
Vol 30 (6) ◽  
pp. 1187-1190 ◽  
Author(s):  
A. J. Seriff ◽  
C. J. Velzeboer ◽  
R. J. Haase
Keyword(s):  
Seismic Noise ◽  
P Wave ◽  
Deep Hole ◽  
Frequency Range ◽  
The Past ◽  
Deep Well ◽  
Short Period ◽  
Noise Measurements ◽  
Deep Boreholes

For the past two years we have been engaged in a program of seismic noise measurements in deep boreholes; noise in a frequency range of approximately 0.2 to 5.0 cps has been studied. A special deep‐well seismometer designed by The Geotechnical Corporation has been used for recording noise at depths down to 14,000 ft in cased holes. The seismometer, which has a response almost identical to the typical short‐period Benioff, was clamped to the casing of the deep hole by a mechanical locking arm during observation periods. An identical seismometer has been used as a reference in a 500‐ft hole adjacent to the deep well. A surface array of four vertical Benioff seismometers was also recorded, with one seismometer near the well and three others at distances ranging from 0.5 to 1.0 km. Two horizontal seismometers were stationed near the wellhead.

A Systematic Study of Earthquake Source Mechanism and Regional Stress Field in the Southern Montney Unconventional Play of Northeast British Columbia, Canada

2019 ◽  
Vol 91 (1) ◽  
pp. 195-206 ◽  
Author(s):  
Alireza Babaie Mahani ◽  
Fatemeh Esfahani ◽  
Honn Kao ◽  
Michelle Gaucher ◽  
Mark Hayes ◽  
...  
Keyword(s):  
British Columbia ◽  
Stress Field ◽  
Horizontal Stress ◽  
Strike Slip ◽  
P Wave ◽  
Source Mechanism ◽  
Induced Earthquakes ◽  
Nodal Plane ◽  
Reverse Faulting ◽  
Best Fitting

Abstract We provide a close look at the source mechanism of hydraulically fractured induced earthquakes and the in situ stress field within the southern Montney unconventional play in the northeast British Columbia, Canada. P‐wave first‐motion focal mechanisms were obtained for 66 earthquakes with magnitudes between 1.5 and 4.6. Results show that strike‐slip movement is the prevailing source mechanism for the events in this area, although reverse faulting is also observed for a few earthquakes. The best‐fitting nodal plane mostly strikes at ∼N60° E, with most events having dip angles of >60°. Using the Martinez‐Garzon et al. (2014) stress inversion module, we obtained the orientation of the three principal compressive stress (S1>S2>S3) and the relative intermediate principal stress magnitude (R) in five clusters. Assuming the best‐fitting nodal plane to be the causative fault, R values are mostly between 0.8 and 0.9 suggesting that the magnitude of S2 and S3 are similar, which is consistent with strike‐slip or reverse‐faulting regimes. The plunge of S1 varies between 1° and 3°, with its trend varying between N21°E and N34°E. On the other hand, the plunge of S3 varies between 22° and 50°, with its trend varies between N68°W and N58°W. Following Lund and Townend (2007), we calculated the trend of maximum horizontal stress to vary from N22°E to N33°E, in comparison with the average trend of N41°E from the World Stress Map (Heidbach et al., 2016). Through analysis of the Coulomb failure criterion and Mohr diagrams, we estimated the amount of pore‐pressure increase necessary to initiate shear slip to range between 4 and 29 MPa (average of 14±8  MPa) in the study area.

Revised world seismicity catalog (1950-1997) for strong (Ms ≧ 6) shallow (h ≦ 70 km) earthquakes

1999 ◽  
Vol 89 (2) ◽  
pp. 335-341 ◽  
Author(s):  
Omar J. Pérez
Keyword(s):  
Earthquake Catalog ◽  
Shallow Earthquakes ◽  
Seismicity Rates ◽  
Worldwide Web ◽  
Seismicity Catalog ◽  
International Seismological Centre ◽  
Seismograph Network ◽  
National Earthquake Information Center ◽  
Magnitude Determination ◽  
Scalar Moment

Abstract Using the standard earthquake catalogs provided by the International Seismological Centre (ISC), its predecessor the International Seismological Summary (ISS), and the National Earthquake Information Center (NEIC), I analyze the worldwide consistency of teleseismic reporting, completeness of the seismicity record, and homogeneity of magnitude determination, for strong shallow earthquakes (surface-wave magnitude, Ms ≥ 6; depth, h ≤ 70 km) for the period 1950 to 1997. Under the postulates that the rate of earthquake occurrence for the entire world is constant on a time scale of decades and that well after the installation of the World-Wide Standardized Seismograph Network in the middle 1960s the earthquake catalog for strong (Ms ≥ 6) shocks is complete, and the seismicity rates are typical of all periods in the century, we find that, due to the use of different formulations and criteria to calculate the parameter magnitude, the Ms of moderate (6 ≤ Ms < 7) events during the period 1950 to 1963 was systematically overestimated by as much as 0.5 magnitude unit, relative to the Ms assigned to shocks occurring after 1963. When this correction is taken into account, the new catalog of events with Ms (corrected) ≥ 6 in the period 1950 to 1997 becomes largely homogeneous in Ms. Under the foregoing postulates, this new catalog is shown to list nearly all and only the strong shocks [Ms (corrected) ≥ 6; h ≤ 70 km] that occurred in the Earth during the period, a notable exception being the time span from 1964 to 1968. The revised catalog, including the scalar moment and moment magnitude for each event, is listed on the worldwide web page http://www.ldc.usb.ve/~ojperez/catalog.

Sign in / Sign up

Export Citation Format

Share Document