Location and Felt Reports for the 25 April 2010 mbLg 3.9 Earthquake Near Alice, Texas: Was it Induced by Petroleum Production?

This study examines seismograms and felt reports for the 25 April 2010 Alice, Texas, earthquake and explores its possible relationship with gas and oil production in the Stratton field. We identified P arrivals at seven broadband stations situated within similar to 100 km of the epicentral region and determined a location of 27.72 degrees N, 97.95 degrees W, about 11 km east of the location reported by the National Earthquake Information Center but coincident with the region of highest intensity (modified Mercalli intensity V-VI) felt reports. We compare arrivals for observed secondary P and S arrivals with predictions from a published Gulf Coast velocity model. At nearby stations, the secondary arrivals are much stronger than primary arrivals; the arrival times and the presence of high-amplitude phases traveling at the Love-wave velocity of the uppermost model layer suggest the focal depth was shallow, 3 km or less. This places the 2010 hypocenter approximately along the mapped trace of the Vicksburg fault zone and at the depth of the Frio formation, the principal productive member in the Stratton field, which has produced at least 2.7 trillion cubic feet of gas and about 100 million barrels of oil since production commenced in 1938. We conclude it is plausible, although not proven definitively, that production in the Stratton field contributed to the occurrence of the 2010 Alice earthquake and an earlier similar earthquake that occurred on 24 March 1997.Ewing-Worzel Summer FellowshipU.S. Geological Survey (USGS), Department of the Interior, under USGS G12AP20001Institute for Geophysic

STRATA-VARIOUS: A flexible Fortran program for dynamic forward modeling of stratigraphy

STRATA-VARIOUS version 1.3 is a computer program written in Fortran 77 to perform two-dimensional forward modeling of stratigraphic processes. We designed specific features of the program to investigate orbital forcing of high-frequency glacioeustasy. This requires forward modeling of many hundreds of sea-level stillstands and the graphic display of relatively precise spatial details. To use this program, the user constructs files that specify the times and elevations of sea-level stillstands, the initial basement topography, numerous parameters that control the geometry and physical properties of stratigraphic beds, the isostatic response of the lithosphere, the pattern of tectonic subsidence and uplift, the number and scale of desired output cross sections, etc. Two features of this program are especially novel. Whereas many forward-modeling programs store information about stratigraphic beds in fixed-size horizontal bins, our program retains in memory the precise locations of all horizontal locations where any stratigraphic bed undergoes any distinct change. This allows us to obtain regional cross sections and magnified sections that preserve information about the geometry and lithology of individual beds. Second, for clastic sediments we have developed a realistic parametric scheme for describing how sea-level variation affects the sediment discharge rate. The parameters that control this scheme have simple physical interpretations in terms of the dimensions, erosion rates, etc. for the alluvial valley responsible for the sediment supply. In this article we give various examples of STRATA-VARIOUS graphic output to illustrate model sensitivity and to demonstrate some of the options available

STRATA-VARIOUS: A flexible Fortran program for dynamic forward modeling of stratigraphy

STRATA-VARIOUS version 1.3 is a computer program written in Fortran 77 to perform two-dimensional forward modeling of stratigraphic processes. We designed specific features of the program to investigate orbital forcing of high-frequency glacioeustasy. This requires forward modeling of many hundreds of sea-level stillstands and the graphic display of relatively precise spatial details. To use this program, the user constructs files that specify the times and elevations of sea-level stillstands, the initial basement topography, numerous parameters that control the geometry and physical properties of stratigraphic beds, the isostatic response of the lithosphere, the pattern of tectonic subsidence and uplift, the number and scale of desired output cross sections, etc. Two features of this program are especially novel. Whereas many forward-modeling programs store information about stratigraphic beds in fixed-size horizontal bins, our program retains in memory the precise locations of all horizontal locations where any stratigraphic bed undergoes any distinct change. This allows us to obtain regional cross sections and magnified sections that preserve information about the geometry and lithology of individual beds. Second, for clastic sediments we have developed a realistic parametric scheme for describing how sea-level variation affects the sediment discharge rate. The parameters that control this scheme have simple physical interpretations in terms of the dimensions, erosion rates, etc. for the alluvial valley responsible for the sediment supply. In this article we give various examples of STRATA-VARIOUS graphic output to illustrate model sensitivity and to demonstrate some of the options available

The Dallas-Fort Worth Earthquake Sequence: October 2008 through May 2009

This paper describes a sequence of small earthquakes (m(b) <= 3.3) that occurred at the Dallas-Fort Worth Airport, Texas, between 30 October 2008 and 31 May 2009. Analysis of records at regional station WMOK identified more than 180 earthquakes in the sequence; about 90 percent occurred in four clusters on 30 October-1 November, 20 November, 26 December and 15-17 May. After the sequence began, a six-station temporary local network obtained high-quality three-component records for 11 earthquakes occurring between 20 November and 1 December. Analysis of these data demonstrated that all 11 earthquakes originated from a focus near 32.855 degrees N, 97.051 degrees W, with an estimated depth similar to 4.4 km. This location is less than 0.5 km from a well completed in August 2008 that extends to a depth of 4.2 km, drilled to dispose of brines collected during flowback of hydraulic fracturing fluids associated with the production of natural gas. Brine disposal commenced at the well on 12 September 2008. Seismograms and (S-P) intervals for the earthquakes are similar though not identical, and relative locations indicate they occurred along a north-northeast-south-southwest trend with horizontal and vertical dimensions of similar to 1.1 km and 0.2 km, respectively. This trend is approximately coincident with that of a mapped normal fault in the subsurface, and consistent with the maximum horizontal in situ stress direction. Because of the absence of previous historical earthquakes, the proximity of the brine disposal well, and the similarity with other documented cases of induced seismicity, it seems likely that fluid injection induced the 2008-2009 sequence.Bureau of Economic Geolog

Seismic recurrence intervals and timing of aseismic subduction inferred from emerged corals and reefs of the Central Vanuatu (New Hebrides) Frontal Arc

The recognition and dating of corals that have been killed by tectonic uplift allow us to date paleoseismic uplifts in the Vanuatu island arc. We recognize corals that record paleouplifts by their similarity to those known to have died during contemporary sudden uplifts and date them (1) by counting annual coral growth bands (only if part of the coral is alive at the time of collection) or (2) by newly developed techniques for obtaining ^(230)Th ages by mass spectrometry. The mass spectrometric method produces isotopic ages with precisions of ±3 to ±9 years (2σ) in the 0–1000 years B.P. time range. The ^(230)Th ages in this time range appear to be accurate. Samples whose ages are known by counting coral growth bands give ^(230)Th ages that are indistinguishable from their growth band ages. By dividing the average increment of uplift for the latest Holocene uplifts by the mean Holocene uplift rate, we can estimate average seismic uplift recurrence intervals for the past 6000 years. The results for each of four central Vanuatu arc segments are (1) North Santo emerged 1.2 m in 1866 A.D. and 0.6 m 107 years later in 1973 A.D. The average coseismic uplift of 0.9 m and mean Holocene uplift rate of 4.3 mm yr^(−1) suggest a longer recurrence interval of 212 years. (2) South Santo emerged 0.29 m in 1946 and 0.26 m 19 years later in 1965, including the related 1971 event. Here the mean Holocene uplift rate is 5.5 mm yr^(−1). The uplift data suggest a longer average recurrence interval of about 51 years. (3) North Malekula emerged 1.23 m near 1729 A. D. and 1.05 m 236 years later in 1965. The mean Holocene uplift rate of 2.7 mm yr^(−1) and mean coseismic uplift of 1.14 m for dated events suggest a longer recurrence interval of 422 years. (4) Part of southernmost Malekula has uplifted continuously or episodically by about 0.35 m from about 1957 until at least mid-1983 A.D. The maximum uplift of 2.7 mm yr^(−1) occurs near a nest of small earthquakes. Both the earthquakes and rapid uplift suggest that interplate slip beneath south Malekula may be continuous, rather than episodic. Episodes of 0.35 m uplift would have to recur every 130 years to maintain the 2.7 mm yr^(−1) uplift rate. In contrast, we find no evidence of interseismic vertical movements for the other three blocks. The most reasonable interpretation of these results is that the seismic recurrence intervals and processes for accommodation of slip are quite different on adjacent arc segments. We have used the most widely accepted moment magnitude relationship to evaluate the accumulated seismic slip caused by large earthquakes occurring since 1920. In all four arc segments this analysis suggests that the seismically radiated moments account for less than one-third to one-tenth of the slip associated with plate convergence. The similarity between the paleoseismic record of uplifts and the contemporary record of coseismic uplifts suggests that this analysis can be generalized to times before 1920. For the northern three segments of central Vanuatu, aseismic slip probably occurs in the same years as large earthquakes because the contemporary coral record records uplifts only in years having large historic earthquakes. This suggests that aseismic slip is not continuous and does not occur at rates which vary slowly over the course of the earthquake cycle. The south Santo segment may have the highest proportion of seismic slip because the mean recurrence interval of 51 years is shortest and the mean Holocene uplift rate of at least 5.5 mm yr^(−1) is the fastest

Seismic Vulnerability and Post-Event Actions for Texas Bridge Infrastructure

0-6916The research investigates the seismic vulnerability of bridges in Texas by characterizing seismic hazards in the State, developing computational tools to estimate the likelihood of seismic damage to various bridge types, and providing the Texas Department of Transportation (TxDOT) tools to inform post-earthquake response planning and decision-making

Modelling human choices: MADeM and decision‑making

Research supported by FAPESP 2015/50122-0 and DFG-GRTK 1740/2. RP and AR are also part of the Research, Innovation and Dissemination Center for Neuromathematics FAPESP grant (2013/07699-0). RP is supported by a FAPESP scholarship (2013/25667-8). ACR is partially supported by a CNPq fellowship (grant 306251/2014-0)

Review: Resource Letter Ps-2: Physics Of Sports

This Resource Letter provides a guide to the literature on the physics of sports, updating Resource Letter PS-1, published 25 years ago (Ref. 17). The intent is to suggest literature for anyone curious about the basic physics of particular sports, for physics teachers searching for sports examples to augment their teaching, and for physicists contemplating research on unsolved sports-related questions. (C) 2011 American Association of Physics Teachers. [DOI: 10.1119/1.3552157]Institute for Geophysic