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Evaluating Spatial and Temporal Relations between an Earthquake Cluster near Entiat, Central Washington, and the Large December 1872 Entiat Earthquake

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We investigate spatial and temporal relations between an ongoing and prolific seismicity cluster in central Washington, near Entiat, and the 14 December 1872 Entiat earthquake, the largest historic crustal earthquake in Washington. A fault scarp produced by the 1872 earthquake lies within the Entiat cluster; the locations and areas of both the cluster and the estimated 1872 rupture surface are comparable. Seismic intensities and the 1–2 m of coseismic displacement suggest a magnitude range between 6.5 and 7.0 for the 1872 earthquake. Aftershock forecast models for (1) the first several hours following the 1872 earthquake, (2) the largest felt earthquakes from 1900 to 1974, and (3) the seismicity within the Entiat cluster from 1976 through 2016 are also consistent with this magnitude range. Based on this aftershock modeling, most of the current seismicity in the Entiat cluster could represent aftershocks of the 1872 earthquake. Other earthquakes, especially those with long recurrence intervals , have long-lived aftershock sequences, including the M w 7.5 1891 Nobi earthquake in Japan, with aftershocks continuing 100 yrs after the mainshock. Although we do not rule out ongoing tectonic deformation in this region, a long-lived aftershock sequence can account for these observations. Electronic Supplement: Interpretation of aeromagnetic data in the vicinity of the Entiat seismicity cluster and the 1872 earthquake.
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The Omori formula n(t)=K(t+c)-1 and its modified form n(t)=K(t+c)-P have been successfully applied to many aftershock sequences since the former was proposed just 100 years ago. This paper summarizes studies using these formulae. The problems of fitting these formulae and related point process models to observational data are discussed mainly. Studies published during the last 1/3 century confirmed that the modified Omori formula generally provides an appropriate representation of the temporal variation of aftershock activity. Although no systematic dependence of the index p has been found on the magnitude of the main shock and on the lowest limit of magnitude above which aftershocks are counted, this index (usually p = 0.9-1.5) differs from sequence to. sequence. This variability may be related to the tectonic condition of the region such as structural heterogeneity, stress, and temperature, but it is not clear which factor is most significant in controlling the p value. The constant c is a controversial quantity. It is strongly influenced by incomplete detection of small aftershocks in the early stage of sequence. Careful analyses indicate that c is positive at least for some sequences. Point process models for the temporal pattern of shallow seismicity must include the existence of aftershocks, most suitably expressed by the modified Omori law. Among such models, the ETAS model seems to best represent the main features of seismicity with only five parameters. An anomalous decrease in aftershock activity below the level predicted by the modified Omori formula sometimes precedes a large aftershock. An anomalous decrease in seismic activity of a region below the level predicted by the ETAS model is sometimes followed by a large earthquake in the same or in a neighboring region.
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The International Seismological Centre, in collaboration with the Global Earthquake Model effort, has released a new global earthquake catalog, covering the time period from 1900 through the end of 2009. In order to use this catalog for global earthquake studies, I determined the magnitude of completeness (M-c) as a function of time by dividing the earthquakes shallower than 60 km into seven time periods based on major changes in catalog processing and data availability and applying four objective methods to determine M-c, with uncertainties determined by nonparametric bootstrapping. Deeper events were divided into two time periods. Because of differences between the four methods, the final M-c was determined subjectively by examining the main features of each method in both the cumulative and binned magnitude-frequency distributions. The time periods and Mc values for shallow events are 1900-1917, M-c = 7.7; 1918-1939, M-c = 7.0; 1940-1954, M-c = 6.8; 1955-1963, M-c = 6.5; 1964-1975, M-c = 6.0; 1976-2003, M-c = 5.8; and 2004-2009, M-c = 5.7. Using these M-c values for the longest time periods for which they are valid (e.g., 1918-2009, 1940-2009, ...), the shallow data fits a Gutenberg-Richter distribution with b = 1.05 and a = 8.3, within 1 standard deviation and with no declustering. The exception is for time periods that include 1900-1917, during which there are only 33 events with M >= M-c and, for those few data, b = 2.15 +/- 0.46. That result calls for further investigations for this time period, ideally having a larger number of earthquakes. For deep events, the results are M-c = 7.1 for 1900-1963 (although the early data are problematic) and M-c = 5.7 for 1964-2009. For the later time period, b = 0.99 and a = 7.3.
Article
The extent to which ongoing seismicity in intraplate regions represents long-lived aftershock activity is unclear. We examined historical and instrumental seismicity in the New Madrid central U.S. region to determine whether present-day seismicity is composed predominantly of aftershocks of the 1811–1812 earthquake sequence. High aftershock productivity is required both to match the observation of multiple mainshocks and to explain the modern level of activity as aftershocks; synthetic sequences consistent with these observations substantially overpredict the number of events of magnitude ≥ 6 that were observed in the past 200 years. Our results imply that ongoing background seismicity in the New Madrid region is driven by ongoing strain accrual processes and that, despite low deformation rates, seismic activity in the zone is not decaying with time.
Article
Generic Mapping Tools (GMT) is an open-source software package for the analysis and display of geoscience data, helping scientists to analyze, interpolate, filter, manipulate, project, and plot time series and gridded data sets. The GMT toolbox includes about 80 core and 40 supplemental program modules sharing a common set of command options, file structures, and documentation. Its power to process data and produce publication-quality graphic presentations has made it vital to a large scientific community that now includes more than 25,000 individual users. GMT's website (http://gmt.soest.hawaii.edu/) exceeds 20,000 visits per month, and server logs show roughly 2000 monthly downloads.
Article
Intensity data from 14 historic earthquakes in or near Washington State, as reported at over 300 localities, are used to study the attenuation structure in Washington. The empirical relation of Evernden (Bull. Seism. Soc. Am., 65, 1287-1313(1975)) is used to determine the size and depth for each earthquake and the local attenuation factor, k, for two physiographic parts of the state. The value for k in the Puget Sound region and north into Canada is 1 3/4, while k = 1 1/2 is more appropriate for eastern Washington and northern Oregon. Individual amplification factors are computed for all localities at which four or more earthquakes have been felt by averaging the difference between the computed intensity and reported intensity at each site. Using these correction factors, the intensities for the North Cascade earthquake of 1872 are used to place constraints on its size and location. It appears this earthquake may be slightly larger (magnitude 7.4) and located south and west of the original epicenter determined by Milne. 7 figures, 4 tables.
Article
A straightforward method for computing rates of slip from earthquakes in major fault zones is presented. The slip rate is calculated from the sum of moments for the earthquakes. Rates obtained are in approximate agreement with rates obtained from geodetic measurements or magnetic anomalies, provided that long time samples are considered and provided that adjustments are made in the vertical extent of the zone of earthquake generation. For some fault zones, particularly deep island arc shear zones, strain is perhaps being relieved by steady creep, whereas, in other fault zones, e.g., the San Andreas, strain is accumulating for a large earthquake. The zone of earthquake generation for oceanic transform faults may be as little as 5 km in vertical extent.
Article
Using a magnitude (M)-log area (A) dataset augmented with seven large (M > 7.0) earthquakes occurring since Wells and Coppersmith (1994), this short note assesses the current validity of the bilinear M-log A relations for continental, strike-slip earthquakes proposed by Hanks and Bakun (2002), in particular the L-model scaling at M > 7. The relations determined by Hanks and Bakun (2002) are only insignificantly altered, leaving these bilinear M-log A relations as valid now as when first proposed.
Article
The Wells and Coppersmith (1994) M -log A data set for continental earthquakes (where M is moment magnitude and A is fault area) and the regression lines derived from it are widely used in seismic hazard analysis for estimating M , given A . Their relations are well determined, whether for the full data set of all mechanism types or for the subset of strike-slip earthquakes. Because the coefficient of the log A term is essentially 1 in both their relations, they are equivalent to constant stress-drop scaling, at least for M ≤ 7, where most of the data lie. For M > 7, however, both relations increasingly underestimate the observations with increasing M . This feature, at least for strike-slip earthquakes, is strongly suggestive of L-model scaling at large M . Using constant stress-drop scaling (Δσ = 26.7 bars) for M ≤ 6.63 and L-model scaling (average fault slip ū = α L , where L is fault length and α = 2.19 &times 10-5) at larger M , we obtain the relations \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[\mathbf{M}=\mathrm{log}{\ }A+3.98{\pm}0.03,{\ }A{\leq}537{\ }\mathrm{km}^{2}\] \end{document} and \batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[\mathbf{M}=4{/}3{\ }\mathrm{log}{\ }A+3.07{\pm}0.04,{\ }A{>}537{\ }\mathrm{km}^{2}.\] \end{document} These prediction equations of our bilinear model fit the Wells and Coppersmith (1994) data set well in their respective ranges of validity, the transition magnitude corresponding to A = 537 km2 being M = 6.71. Manuscript received 15 April 2001.
Article
Seismicity is modeled as a sequence of earthquake nucleation events in which the distribution of initial conditions over the population of nucleation sources and stressing history control the timing of earthquakes. The model is implemented using solutions for nucleation of unstable fault slip on faults with experimentally derived rate- and state-dependent fault properties. This yields a general state-variable constitutive formulation for rate of earthquake production resulting from an applied stressing history. To illustrate and test the model some characteristics of seismicity following a stress step have been explored. It is proposed that various features of earthquake clustering arise from sensitivity of nucleation times to the stress changes induced by prior earthquakes. The model gives the characteristic Omori aftershock decay law and interprets aftershock parameters in terms of stress change and stressing rate. Earthquake data appear to support a model prediction that aftershock duration, defined as the time for rates to return to the back-ground seismicity rate, is proportional to mainshock recurrence time. Observed spatial and temporal clustering of earthquake pairs arises as a consequence of the spatial dependence of stress changes of the first event of the pair and stress-sensitive time-dependent nucleation. Applications of the constitutive formulation are not restricted to the simple stress step models investigated here. It may be applied to stressing histories of arbitrary complexity. The apparent success at modeling clustering phenomena suggests the possibility of using the formulation to estimate short- to intermediate-term earthquake probabilities following occurrence of other earthquakes and for inversion of temporal variations of earthquake rates for changes in driving stress.
Article
Statistical seismology is critical to the understanding of seismicity, the testing of proposed earthquake prediction and forecasting methods, and the assessment of seismic hazard. Unfortunately, despite its importance to seismology - especially to those aspects with great impact on public policy - statistical seismology is mostly ignored in the education of seismologists, and there is no central repository for the existing open-source software tools. To remedy these deficiencies, and with the broader goal to enhance the quality of statistical seismology research, we have begun building the Community Online Resource for Statistical Seismicity Analysis (CORSSA). CORSSA is a web-based educational platform that is authoritative, up-to-date, prominent, and user-friendly. We anticipate that the users of CORSSA will range from beginning graduate students to experienced researchers. More than 20 scientists from around the world met for a week in Zurich in May 2010 to kick-start the creation of CORSSA: the format and initial table of contents were defined; a governing structure was organized; and workshop participants began drafting articles. CORSSA materials are organized with respect to six themes, each containing between four and eight articles. The CORSSA web page, www.corssa.org, officially unveiled on September 6, 2010, debuts with an initial set of approximately 10 to 15 articles available online for viewing and commenting with additional articles to be added over the coming months. Each article will be peer-reviewed and will present a balanced discussion, including illustrative examples and code snippets. Topics in the initial set of articles will include: introductions to both CORSSA and statistical seismology, basic statistical tests and their role in seismology; understanding seismicity catalogs and their problems; basic techniques for modeling seismicity; and methods for testing earthquake predictability hypotheses. A special article will compare and review available statistical seismology software packages.
Article
The historical and instrumental records of earthquakes were used to estimate earthquake recurrence rates for input to a new seismic hazard analysis at the Hanford Site in eastern Washington. Two areas were evaluated, the eastern Washington region and the smaller Yakima Fold Belt, in which the Hanford Site is located. The completeness of a catalog of earthquakes was evaluated for earthquakes with Modified Mercalli Intensity (MMI) IV through VII. Only one MMI VII earthquake was reported in the last 100 years in eastern Washington. The reporting of MMI VI earthquakes appears to be complete for the last 80 years, and the reporting of MMI V earthquakes appears to be complete for the last 65 years. However, MMI IV earthquakes are consistently under-reported. For a limited set of earthquakes, both MMI and magnitude (M/sub L/) have been reported. A plot of these data indicated that the Gutenberg-Richter relationship could be used to estimate earthquakes magnitudes from intensities. A recurrence curve for the historical earthquake data was calculated using the maximum likelihood method, including corrections for the width of the magnitude conversion. The slope of the recurrence curve (i.e., b-value) was found to be -1.15. Another catalog, one that listed instrumentally detected earthquakes from 1969 to the present, was used to supplement the historical earthquake data. Magnitudes were determined using a coda-length method (M/sub c/) that had been approximately calibrated to local magnitude M/sub L/. For earthquakes whose M/sub c/ was between 3 and 5, the b-value ranged from -1.07 to - 1.12. 12 refs., 9 figs., 9 tabs.
Article
The large dispersion of data for components of earthquake motion requires that the spread be appraised in design applications. Instrumental data also must be related to historic records of intensity. The near field and the far field contribute greatly to differences in peak motions. Site conditions, soil versus rock, affect duration. With these considerations, and with geological studies and the probability of recurrence, peak values can be specified from parameters of motions related to Modified Mercalli intensities. These peak values can be used for rescaling selected strong motion records or alternatively for the generation of synthetic seismograms. The procedure incorporates the wide variability in ground motions that have occurred during earthquakes. (Author)
Article
After a strong earthquake, the possibility of the occurrence of either significant aftershocks or an even stronger mainshock is a continuing hazard that threatens the resumption of critical services and reoccupation of essential but partially damaged structures. A stochastic parametric model allows determination of probabilities for aftershocks and larger mainshocks during intervals following the mainshock. The probabilities depend strongly on the model parameters, which are estimated with Bayesian statistics from both the ongoing aftershock sequence and from a suite of historic California aftershock sequences. Probabilities for damaging aftershocks and greater mainshocks are typically well-constrained after the first day of the sequence, with accuracy increasing with time.
The December 14, 1872, earthquake in the Pacific Northwest
  • S T Hopper
  • D M Algermissen
  • S R Perkins
  • E P Brockman
  • Arnold
The other data are available in the unpublished USGS openfile report by M. G. Hopper, S. T. Algermissen, D. M. Perkins, S. R. Brockman, and E. P. Arnold (2003), "The December 14, 1872, earthquake in the Pacific Northwest", and in the unpublished manuscript by B. L. Sherrod, R. J. Blakely, and C. S.
Active faulting in the northern Juan de Fuca Strait, implications for Victoria
  • V Barrie
  • G Greene
Barrie, V., and G. Greene (2015). Active faulting in the northern Juan de Fuca Strait, implications for Victoria, British Columbia, Geol. Surv. Can. Curr. Res. 2015-6, 10, doi: 10.4095/296564.
Scaling for seismic source spectra and energy attenuation in the Chelan Region, eastern Washington
  • S S Bor
Bor, S. S. (1977). Scaling for seismic source spectra and energy attenuation in the Chelan Region, eastern Washington, Master Dissertation, University of Washington, Seattle, 65 pp.
Active fault monitoring using portable seismograph arrays in Washington State
  • R Cakir
  • S Scott
  • T J Walsh
  • T Lau
  • K Szatkowski
  • J Dragovich
  • M L Anderson
  • M Polenz
  • S Mavor
  • M Allen
Cakir, R., S. Scott, T. J. Walsh, T. Lau, K. Szatkowski, J. Dragovich, M. L. Anderson, M. Polenz, S. Mavor, and M. Allen (2016). Active fault monitoring using portable seismograph arrays in Washington State, Eos Trans. AGU 98, Abstract T41A-2892.
Reportof the Review Panel on the December 14, 1872 earthquake in Washington Public Power Supply System Nuclear Projects Nos. 1 and 4, Preliminary Site Analysis Report
  • H A Coombs
  • W G Milne
  • O W Nuttli
  • D B Slemmons
Coombs,H.A., W. G.Milne,O.W. Nuttli, and D.B.Slemmons(1976). Reportof the Review Panel on the December 14, 1872 earthquake in Washington Public Power Supply System Nuclear Projects Nos. 1 and 4, Preliminary Site Analysis Report, Amendment 23, Vol. 2A, Sub-appendix 2R-A, 30 pp., Appendix B, Reports related to the December 14, 1872 earthquake, 247 pp., Report to the Nuclear RegulatoryCommission, Washington, D.C.
The Chelan seismic zone, the Great Terrace and the December 1872 Washington State
  • J G Crider
  • R S Crosson
  • J Brooks
Crider, J. G., R. S. Crosson, and J. Brooks (2003). The Chelan seismic zone, the Great Terrace and the December 1872 Washington State, Geol. Soc. Am. Abstr. Progr. 35, no. 6, 645.
An InSAR analysis of surface deformation associated with the Chelan seismic zone, central Washington
  • A Diefenbach
  • J G Crider
  • M Poland
Diefenbach, A., J. G. Crider, and M. Poland (2007). An InSAR analysis of surface deformation associated with the Chelan seismic zone, central Washington, Proc. of the GSA Cordilleran Section 103rd Annual Meeting, Geol. Soc. Am., Bellingham, Washington, 4-6 May.
Seismic Activity in Canada West of the 113th Meridian
  • W G Milne
Milne, W. G. (1956). Seismic Activity in Canada West of the 113th Meridian, 1841-1951, Vol. 18, Dominion Observatory Publications, Ottawa, Canada, 126-127.
LiDAR helps identify source of 1872 earthquake near Chelan
  • B L Sherrod
  • R J Blakely
  • C S Weaver
Sherrod, B. L., R. J. Blakely, and C. S. Weaver (2015). LiDAR helps identify source of 1872 earthquake near Chelan, Eos Trans. AGU 97, Abstract T31A-2826.