The Moment Magnitude and the Energy Magnitude: Common Roots
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New Empirical Relationships Among Magnitude, Rupture Length, Rupture Width, Rupture Area, and Surface Displacement
Bulletin of the Seismological Society of America, Vol. 84, No. 4, pp. 974-1002, August 1994 New Empirical Relationships among Magnitude, Rupture Length, Rupture Width, Rupture Area, and Surface Displacement by Donald L. Wells and Kevin J. Coppersmith Abstract Source parameters for historical earthquakes worldwide are com piled to develop a series of empirical relationships among moment magnitude (M), surface rupture length, subsurface rupture length, downdip rupture width, rupture area, and maximum and average displacement per event. The resulting data base is a significant update of previous compilations and includes the ad ditional source parameters of seismic moment, moment magnitude, subsurface rupture length, downdip rupture width, and average surface displacement. Each source parameter is classified as reliable or unreliable, based on our evaluation of the accuracy of individual values. Only the reliable source parameters are used in the final analyses. In comparing source parameters, we note the fol lowing trends: (1) Generally, the length of rupture at the surface is equal to 75% of the subsurface rupture length; however, the ratio of surface rupture length to subsurface rupture length increases with magnitude; (2) the average surface dis placement per event is about one-half the maximum surface displacement per event; and (3) the average subsurface displacement on the fault plane is less than the maximum surface displacement but more than the average surface dis placement. Thus, for most earthquakes in this data base, slip on the fault plane at seismogenic depths is manifested by similar displacements at the surface. Log-linear regressions between earthquake magnitude and surface rupture length, subsurface rupture length, and rupture area are especially well correlated, show ing standard deviations of 0.25 to 0.35 magnitude units. -
Earthquake Rupture on Multiple Splay Faults and Its Effect on Tsunamis
manuscript submitted to Geophysical Research Letters 1 Earthquake rupture on multiple splay faults and its 2 effect on tsunamis 1;2 3 4 1;5 3 I. van Zelst , L. Rannabauer , A.-A. Gabriel , Y. van Dinther 1 4 Seismology and Wave Physics, Institute of Geophysics, Department of Earth Sciences, ETH Z¨urich, 5 Z¨urich, Switzerland 2 6 Institute of Geophysics and Tectonics, School of Earth and Environment, University of Leeds, Leeds, LS2 7 9JT, United Kingdom 3 8 Department of Informatics, Technical University of Munich, Munich, Germany 4 9 Geophysics, Department of Earth and Environmental Sciences, LMU Munich, Munich, Germany 5 10 Department of Earth Sciences, Utrecht University, Utrecht, The Netherlands 11 Key Points: 12 • Multiple splay faults can be activated during an earthquake by slip on the megath- 13 rust, dynamic stress transfer, or stress changes from waves 14 • Splay fault activation is partially facilitated by their alignment with the local stress 15 field and closeness to failure 16 • The tsunami has a high crest due to slip on the longest splay fault and a second 17 broad wave packet due to slip on multiple smaller faults Corresponding author: Iris van Zelst, [email protected] / [email protected] {1{ manuscript submitted to Geophysical Research Letters 18 Abstract 19 Detailed imaging of accretionary wedges reveal complex splay fault networks which 20 could pose a significant tsunami hazard. However, the dynamics of multiple splay fault 21 activation and interaction during megathrust events and consequent effects on tsunami 22 generation are not well understood. We use a 2D dynamic rupture model with six com- 23 plex splay fault geometries consistent with initial stress and strength conditions constrained 24 by a geodynamic seismic cycle model. -
The 2018 Mw 7.5 Palu Earthquake: a Supershear Rupture Event Constrained by Insar and Broadband Regional Seismograms
remote sensing Article The 2018 Mw 7.5 Palu Earthquake: A Supershear Rupture Event Constrained by InSAR and Broadband Regional Seismograms Jin Fang 1, Caijun Xu 1,2,3,* , Yangmao Wen 1,2,3 , Shuai Wang 1, Guangyu Xu 1, Yingwen Zhao 1 and Lei Yi 4,5 1 School of Geodesy and Geomatics, Wuhan University, Wuhan 430079, China; [email protected] (J.F.); [email protected] (Y.W.); [email protected] (S.W.); [email protected] (G.X.); [email protected] (Y.Z.) 2 Key Laboratory of Geospace Environment and Geodesy, Ministry of Education, Wuhan University, Wuhan 430079, China 3 Collaborative Innovation Center of Geospatial Technology, Wuhan University, Wuhan 430079, China 4 Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China; [email protected] 5 Qinghai Provincial Key Laboratory of Geology and Environment of Salt Lakes, Qinghai Institute of Salt Lakes, Chinese Academy of Sciences, Xining 810008, China * Correspondence: [email protected]; Tel.: +86-27-6877-8805 Received: 4 April 2019; Accepted: 29 May 2019; Published: 3 June 2019 Abstract: The 28 September 2018 Mw 7.5 Palu earthquake occurred at a triple junction zone where the Philippine Sea, Australian, and Sunda plates are convergent. Here, we utilized Advanced Land Observing Satellite-2 (ALOS-2) interferometry synthetic aperture radar (InSAR) data together with broadband regional seismograms to investigate the source geometry and rupture kinematics of this earthquake. Results showed that the 2018 Palu earthquake ruptured a fault plane with a relatively steep dip angle of ~85◦. -
Earthquake Measurements
EARTHQUAKE MEASUREMENTS The vibrations produced by earthquakes are detected, recorded, and measured by instruments call seismographs1. The zig-zag line made by a seismograph, called a "seismogram," reflects the changing intensity of the vibrations by responding to the motion of the ground surface beneath the instrument. From the data expressed in seismograms, scientists can determine the time, the epicenter, the focal depth, and the type of faulting of an earthquake and can estimate how much energy was released. Seismograph/Seismometer Earthquake recording instrument, seismograph has a base that sets firmly in the ground, and a heavy weight that hangs free2. When an earthquake causes the ground to shake, the base of the seismograph shakes too, but the hanging weight does not. Instead the spring or string that it is hanging from absorbs all the movement. The difference in position between the shaking part of the seismograph and the motionless part is Seismograph what is recorded. Measuring Size of Earthquakes The size of an earthquake depends on the size of the fault and the amount of slip on the fault, but that’s not something scientists can simply measure with a measuring tape since faults are many kilometers deep beneath the earth’s surface. They use the seismogram recordings made on the seismographs at the surface of the earth to determine how large the earthquake was. A short wiggly line that doesn’t wiggle very much means a small earthquake, and a long wiggly line that wiggles a lot means a large earthquake2. The length of the wiggle depends on the size of the fault, and the size of the wiggle depends on the amount of slip. -
Energy and Magnitude: a Historical Perspective
Pure Appl. Geophys. 176 (2019), 3815–3849 Ó 2018 Springer Nature Switzerland AG https://doi.org/10.1007/s00024-018-1994-7 Pure and Applied Geophysics Energy and Magnitude: A Historical Perspective 1 EMILE A. OKAL Abstract—We present a detailed historical review of early referred to as ‘‘Gutenberg [and Richter]’s energy– attempts to quantify seismic sources through a measure of the magnitude relation’’ features a slope of 1.5 which is energy radiated into seismic waves, in connection with the parallel development of the concept of magnitude. In particular, we explore not predicted a priori by simple physical arguments. the derivation of the widely quoted ‘‘Gutenberg–Richter energy– We will use Gutenberg and Richter’s (1956a) nota- magnitude relationship’’ tion, Q [their Eq. (16) p. 133], for the slope of log10 E versus magnitude [1.5 in (1)]. log10 E ¼ 1:5Ms þ 11:8 ð1Þ We are motivated by the fact that Eq. (1)istobe (E in ergs), and especially the origin of the value 1.5 for the slope. found nowhere in this exact form in any of the tra- By examining all of the relevant papers by Gutenberg and Richter, we note that estimates of this slope kept decreasing for more than ditional references in its support, which incidentally 20 years before Gutenberg’s sudden death, and that the value 1.5 were most probably copied from one referring pub- was obtained through the complex computation of an estimate of lication to the next. They consist of Gutenberg and the energy flux above the hypocenter, based on a number of assumptions and models lacking robustness in the context of Richter (1954)(Seismicity of the Earth), Gutenberg modern seismological theory. -
Relation of Slow Slip Events to Subsequent Earthquake Rupture
Earthquake and tsunami forecasts: Relation of slow slip events to subsequent earthquake rupture Timothy H. Dixona,1, Yan Jiangb, Rocco Malservisia, Robert McCaffreyc, Nicholas Vossa, Marino Prottid, and Victor Gonzalezd aSchool of Geosciences, University of South Florida, Tampa, FL 33620; bPacific Geoscience Centre, Geological Survey of Canada, BC, Canada V8L 4B2; cDepartment of Geology, Portland State University, Portland, OR 97201; and dObservatorio Vulcanológico y Sismológico de Costa Rica, Universidad Nacional, Heredia 3000, Costa Rica Edited* by David T. Sandwell, Scripps Institution of Oceanography, La Jolla, CA, and approved October 24, 2014 (received for review June 30, 2014) The 5 September 2012 Mw 7.6 earthquake on the Costa Rica sub- Geologic and Seismic Background duction plate boundary followed a 62-y interseismic period. High- The Nicoya Peninsula forms the western edge of the Caribbean precision GPS recorded numerous slow slip events (SSEs) in the plate, where the Cocos plate subducts beneath the Caribbean decade leading up to the earthquake, both up-dip and down-dip plate along the Middle American Trench at about 8 cm/y (3). The of seismic rupture. Deeper SSEs were larger than shallower ones region has a well-defined earthquake cycle, with large (M > 7) and, if characteristic of the interseismic period, release most lock- earthquakes in 1853, 1900, 1950 (M 7.7), and most recently 5 ing down-dip of the earthquake, limiting down-dip rupture and September 2012 (Mw 7.6). Smaller (M ∼ 7) events in 1978 and earthquake magnitude. Shallower SSEs were smaller, accounting 1990 have also occurred nearby (4). Large tsunamis have not for some but not all interseismic locking. -
Fully-Coupled Simulations of Megathrust Earthquakes and Tsunamis in the Japan Trench, Nankai Trough, and Cascadia Subduction Zone
Noname manuscript No. (will be inserted by the editor) Fully-coupled simulations of megathrust earthquakes and tsunamis in the Japan Trench, Nankai Trough, and Cascadia Subduction Zone Gabriel C. Lotto · Tamara N. Jeppson · Eric M. Dunham Abstract Subduction zone earthquakes can pro- strate that horizontal seafloor displacement is a duce significant seafloor deformation and devas- major contributor to tsunami generation in all sub- tating tsunamis. Real subduction zones display re- duction zones studied. We document how the non- markable diversity in fault geometry and struc- hydrostatic response of the ocean at short wave- ture, and accordingly exhibit a variety of styles lengths smooths the initial tsunami source relative of earthquake rupture and tsunamigenic behavior. to commonly used approach for setting tsunami We perform fully-coupled earthquake and tsunami initial conditions. Finally, we determine self-consistent simulations for three subduction zones: the Japan tsunami initial conditions by isolating tsunami waves Trench, the Nankai Trough, and the Cascadia Sub- from seismic and acoustic waves at a final sim- duction Zone. We use data from seismic surveys, ulation time and backpropagating them to their drilling expeditions, and laboratory experiments initial state using an adjoint method. We find no to construct detailed 2D models of the subduc- evidence to support claims that horizontal momen- tion zones with realistic geometry, structure, fric- tum transfer from the solid Earth to the ocean is tion, and prestress. Greater prestress and rate-and- important in tsunami generation. state friction parameters that are more velocity- weakening generally lead to enhanced slip, seafloor Keywords tsunami; megathrust earthquake; deformation, and tsunami amplitude. -
Rapid Identification of Tsunamigenic Earthquakes Using GNSS
www.nature.com/scientificreports OPEN Rapid identifcation of tsunamigenic earthquakes using GNSS ionospheric sounding Fabio Manta1,2,4*, Giovanni Occhipinti 3,4, Lujia Feng 1 & Emma M. Hill 1,2 The largest tsunamis are generated by seafoor uplift resulting from rupture of ofshore subduction- zone megathrusts. The rupture of the shallowest part of a megathrust often produces unexpected outsize tsunami relative to their seismic magnitude. These are so called ‘tsunami earthquakes’, which are difcult to identify rapidly using the current tsunami warning systems, even though, they produce some of the deadliest tsunami. We here introduce a new method to evaluate the tsunami risk by measuring ionospheric total electron content (TEC). We examine two Mw 7.8 earthquakes (one is a tsunami earthquake and the other is not) generated in 2010 by the Sunda megathrust, ofshore Sumatra, to demonstrate for the frst time that observations of ionospheric sounding from Global Navigation Satellite System (GNSS) can be used to evaluate the tsunamigenic potential of earthquakes as early as 8 min after the mainshock. ‘Tsunami earthquakes’, as originally defned by Kanamori 1, are events generating tsunami with larger amplitude than expected from their seismic magnitude. Most tsunami earthquakes are generated by high levels of slip on the shallow megathrust, which results in large seafoor uplifs and hence very dangerous tsunami. Te shallow location of the slip—close to the subduction trench—means that the ruptures generating tsunami earthquakes are at signifcant distance from land-based monitoring networks, limiting our ability to quickly and accurately assess their magnitude and source parameters. Conventional approaches using various seismological methods2–4 or rapid inversion of GNSS (Global Navigation Satellite System) estimates of ground motion5 regularly encounter difculties in accurately estimating the uplif of the seafoor and consequently fail in predicting the tsunamigenic nature of tsunami earthquakes. -
Rupture Process of the 2019 Ridgecrest, California Mw 6.4 Foreshock and Mw 7.1 Earthquake Constrained by Seismic and Geodetic Data, Bull
Rupture process of the 2019 Ridgecrest, M M California w 6.4 Foreshock and w 7.1 Earthquake Constrained by Seismic and Geodetic Data Kang Wang*1,2, Douglas S. Dreger1,2, Elisa Tinti3,4, Roland Bürgmann1,2, and Taka’aki Taira2 ABSTRACT The 2019 Ridgecrest earthquake sequence culminated in the largest seismic event in California M since the 1999 w 7.1 Hector Mine earthquake. Here, we combine geodetic and seismic data M M to study the rupture process of both the 4 July w 6.4 foreshock and the 6 July w 7.1 main- M shock. The results show that the w 6.4 foreshock rupture started on a northwest-striking right-lateral fault, and then continued on a southwest-striking fault with mainly left-lateral M slip. Although most moment release during the w 6.4 foreshock was along the southwest- striking fault, slip on the northwest-striking fault seems to have played a more important role M ∼ M in triggering the w 7.1 mainshock that happened 34 hr later. Rupture of the w 7.1 main- shock was characterized by dominantly right-lateral slip on a series of overall northwest- striking fault strands, including the one that had already been activated during the nucleation M ∼ of the w 6.4 foreshock. The maximum slip of the 2019 Ridgecrest earthquake was 5m, – M located at a depth range of 3 8kmnearthe w 7.1 epicenter, corresponding to a shallow slip deficit of ∼ 20%–30%. Both the foreshock and mainshock had a relatively low-rupture veloc- ity of ∼ 2km= s, which is possibly related to the geometric complexity and immaturity of the eastern California shear zone faults. -
This Article Was Published in an Elsevier Journal. the Attached Copy Is Furnished to the Author for Non-Commercial Research
This article was published in an Elsevier journal. The attached copy is furnished to the author for non-commercial research and education use, including for instruction at the author’s institution, sharing with colleagues and providing to institution administration. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier’s archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/copyright Author's personal copy ARTICLE IN PRESS Journal of the Mechanics and Physics of Solids 56 (2008) 25–50 www.elsevier.com/locate/jmps Transition of mode II cracks from sub-Rayleigh to intersonic speeds in the presence of favorable heterogeneity Yi Liua, Nadia Lapustab,Ã aDivision of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125, USA bDivision of Engineering and Applied Science and Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125, USA Received 22 January 2007; received in revised form 8 June 2007; accepted 11 June 2007 Abstract Understanding sub-Rayleigh-to-intersonic transition of mode II cracks is a fundamental problem in fracture mechanics with important practical implications for earthquake dynamics and seismic radiation. In the Burridge–Andrews mechanism, an intersonic daughter crack nucleates, for sufficiently high prestress, at the shear stress peak traveling with the shear wave speed in front of the main crack. -
Earthquake Rupture Below the Brittle-Ductile Transition in Continental Lithospheric Mantle G.A
Earthquake rupture below the brittle-ductile transition in continental lithospheric mantle G.A. Prieto, B. Froment, C. Yu, P. Poli, R. Abercrombie To cite this version: G.A. Prieto, B. Froment, C. Yu, P. Poli, R. Abercrombie. Earthquake rupture below the brittle- ductile transition in continental lithospheric mantle. Science Advances , American Association for the Advancement of Science (AAAS), 2017, 3 (3), pp.e1602642. 10.1126/sciadv.1602642. hal-02546125 HAL Id: hal-02546125 https://hal.archives-ouvertes.fr/hal-02546125 Submitted on 25 Sep 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. SCIENCE ADVANCES | RESEARCH ARTICLE GEOLOGY 2017 © The Authors, some rights reserved; Earthquake rupture below the brittle-ductile transition exclusive licensee American Association in continental lithospheric mantle for the Advancement of Science. Distributed 1 2 3,4 3 5 under a Creative Germán A. Prieto, * Bérénice Froment, Chunquan Yu, Piero Poli, Rachel Abercrombie Commons Attribution NonCommercial Earthquakes deep in the continental lithosphere are rare and hard to interpret in our current understanding of tem- License 4.0 (CC BY-NC). perature control on brittle failure. The recent lithospheric mantle earthquake with a moment magnitude of 4.8 at a depth of ~75 km in the Wyoming Craton was exceptionally well recorded and thus enabled us to probe the cause of these unusual earthquakes. -
A Test for the Mediterranean Tsunami Warning System Mohammad Heidarzadeh1* , Ocal Necmioglu2 , Takeo Ishibe3 and Ahmet C
Heidarzadeh et al. Geosci. Lett. (2017) 4:31 https://doi.org/10.1186/s40562-017-0097-0 RESEARCH LETTER Open Access Bodrum–Kos (Turkey–Greece) Mw 6.6 earthquake and tsunami of 20 July 2017: a test for the Mediterranean tsunami warning system Mohammad Heidarzadeh1* , Ocal Necmioglu2 , Takeo Ishibe3 and Ahmet C. Yalciner4 Abstract Various Tsunami Service Providers (TSPs) within the Mediterranean Basin supply tsunami warnings including CAT-INGV (Italy), KOERI-RETMC (Turkey), and NOA/HL-NTWC (Greece). The 20 July 2017 Bodrum–Kos (Turkey–Greece) earth- quake (Mw 6.6) and tsunami provided an opportunity to assess the response from these TSPs. Although the Bodrum– Kos tsunami was moderate (e.g., runup of 1.9 m) with little damage to properties, it was the frst noticeable tsunami in the Mediterranean Basin since the 21 May 2003 western Mediterranean tsunami. Tsunami waveform analysis revealed that the trough-to-crest height was 34.1 cm at the near-feld tide gauge station of Bodrum (Turkey). Tsunami period band was 2–30 min with peak periods at 7–13 min. We proposed a source fault model for this tsunami with the length and width of 25 and 15 km and uniform slip of 0.4 m. Tsunami simulations using both nodal planes produced almost same results in terms of agreement between tsunami observations and simulations. Diferent TSPs provided tsunami warnings at 10 min (CAT-INGV), 19 min (KOERI-RETMC), and 18 min (NOA/HL-NTWC) after the earthquake origin time. Apart from CAT-INGV, whose initial Mw estimation difered 0.2 units with respect to the fnal value, the response from the other two TSPs came relatively late compared to the desired warning time of ~ 10 min, given the difculties for timely and accurate calculation of earthquake magnitude and tsunami impact assessment.