Foreshock Sequences and Short-Term Earthquake Predictability on East Pacific Rise Transform Faults
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Coulomb Stresses Imparted by the 25 March
LETTER Earth Planets Space, 60, 1041–1046, 2008 Coulomb stresses imparted by the 25 March 2007 Mw=6.6 Noto-Hanto, Japan, earthquake explain its ‘butterfly’ distribution of aftershocks and suggest a heightened seismic hazard Shinji Toda Active Fault Research Center, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology (AIST), site 7, 1-1-1 Higashi Tsukuba, Ibaraki 305-8567, Japan (Received June 26, 2007; Revised November 17, 2007; Accepted November 22, 2007; Online published November 7, 2008) The well-recorded aftershocks and well-determined source model of the Noto Hanto earthquake provide an excellent opportunity to examine earthquake triggering associated with a blind thrust event. The aftershock zone rapidly expanded into a ‘butterfly pattern’ predicted by static Coulomb stress transfer associated with thrust faulting. We found that abundant aftershocks occurred where the static Coulomb stress increased by more than 0.5 bars, while few shocks occurred in the stress shadow calculated to extend northwest and southeast of the Noto Hanto rupture. To explore the three-dimensional distribution of the observed aftershocks and the calculated stress imparted by the mainshock, we further resolved Coulomb stress changes on the nodal planes of all aftershocks for which focal mechanisms are available. About 75% of the possible faults associated with the moderate-sized aftershocks were calculated to have been brought closer to failure by the mainshock, with the correlation best for low apparent fault friction. Our interpretation is that most of the aftershocks struck on the steeply dipping source fault and on a conjugate northwest-dipping reverse fault contiguous with the source fault. -
Intraplate Earthquakes in North China
5 Intraplate earthquakes in North China mian liu, hui wang, jiyang ye, and cheng jia Abstract North China, or geologically the North China Block (NCB), is one of the most active intracontinental seismic regions in the world. More than 100 large (M > 6) earthquakes have occurred here since 23 BC, including the 1556 Huax- ian earthquake (M 8.3), the deadliest one in human history with a death toll of 830,000, and the 1976 Tangshan earthquake (M 7.8) which killed 250,000 people. The cause of active crustal deformation and earthquakes in North China remains uncertain. The NCB is part of the Archean Sino-Korean craton; ther- mal rejuvenation of the craton during the Mesozoic and early Cenozoic caused widespread extension and volcanism in the eastern part of the NCB. Today, this region is characterized by a thin lithosphere, low seismic velocity in the upper mantle, and a low and flat topography. The western part of the NCB consists of the Ordos Plateau, a relic of the craton with a thick lithosphere and little inter- nal deformation and seismicity, and the surrounding rift zones of concentrated earthquakes. The spatial pattern of the present-day crustal strain rates based on GPS data is comparable to that of the total seismic moment release over the past 2,000 years, but the comparison breaks down when using shorter time windows for seismic moment release. The Chinese catalog shows long-distance roaming of large earthquakes between widespread fault systems, such that no M ࣙ 7.0 events ruptured twice on the same fault segment during the past 2,000 years. -
Development of Faults and Prediction of Earthquakes in the Himalayas
Journal of Graphic Era University Vol. 6, Issue 2, 197-206, 2018 ISSN: 0975-1416 (Print), 2456-4281 (Online) Development of Faults and Prediction of Earthquakes in the Himalayas A. K. Dubey Department of Petroleum Engineering Graphic Era Deemed to be University, Dehradun, India E-mail: [email protected] (Received October 9, 2017; Accepted July 3, 2018) Abstract Recurrence period of high magnitude earthquakes in the Himalayas may be of the order of hundreds of years but a large number of smaller earthquakes occur every day. The low intensity earthquakes are not felt by human beings but recorded in sensitive instruments called seismometers. It is not possible to get rid of these earthquakes because the mountain building activity is still going on. Continuous compression and formation of faults in the region is caused by northward movement of the Indian plate. Some of the larger faults extend from Kashmir to Arunachal Pradesh. Strain build up in the region results in displacement along these faults that cause earthquakes. Types of these faults, mechanism of their formation and problems in predicting earthquakes in the region are discussed. Keywords- Faults and faulting, Himalayan thrusts, Oil trap, Seismicity, Superimposed deformation. 1. Introduction If we go back in the history of the Earth (~250 million years ago), India was part of a huge land mass called 'Pangaea'. The land mass was positioned in the southern hemisphere very close to the South pole (Antarctica). Because of some reason, not known to us till now, the landmass broke and India started its onward journey in a northerly direction. -
Seismic Rate Variations Prior to the 2010 Maule, Chile MW 8.8 Giant Megathrust Earthquake
www.nature.com/scientificreports OPEN Seismic rate variations prior to the 2010 Maule, Chile MW 8.8 giant megathrust earthquake Benoit Derode1*, Raúl Madariaga1,2 & Jaime Campos1 The MW 8.8 Maule earthquake is the largest well-recorded megathrust earthquake reported in South America. It is known to have had very few foreshocks due to its locking degree, and a strong aftershock activity. We analyze seismic activity in the area of the 27 February 2010, MW 8.8 Maule earthquake at diferent time scales from 2000 to 2019. We diferentiate the seismicity located inside the coseismic rupture zone of the main shock from that located in the areas surrounding the rupture zone. Using an original spatial and temporal method of seismic comparison, we fnd that after a period of seismic activity, the rupture zone at the plate interface experienced a long-term seismic quiescence before the main shock. Furthermore, a few days before the main shock, a set of seismic bursts of foreshocks located within the highest coseismic displacement area is observed. We show that after the main shock, the seismic rate decelerates during a period of 3 years, until reaching its initial interseismic value. We conclude that this megathrust earthquake is the consequence of various preparation stages increasing the locking degree at the plate interface and following an irregular pattern of seismic activity at large and short time scales. Giant subduction earthquakes are the result of a long-term stress localization due to the relative movement of two adjacent plates. Before a large earthquake, the interface between plates is locked and concentrates the exter- nal forces, until the rock strength becomes insufcient, initiating the sudden rupture along the plate interface. -
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◦. -
BY JOHNATHAN EVANS What Exactly Is an Earthquake?
Earthquakes BY JOHNATHAN EVANS What Exactly is an Earthquake? An Earthquake is what happens when two blocks of the earth are pushing against one another and then suddenly slip past each other. The surface where they slip past each other is called the fault or fault plane. The area below the earth’s surface where the earthquake starts is called the Hypocenter, and the area directly above it on the surface is called the “Epicenter”. What are aftershocks/foreshocks? Sometimes earthquakes have Foreshocks. Foreshocks are smaller earthquakes that happen in the same place as the larger earthquake that follows them. Scientists can not tell whether an earthquake is a foreshock until after the larger earthquake happens. The biggest, main earthquake is called the mainshock. The mainshocks always have aftershocks that follow the main earthquake. Aftershocks are smaller earthquakes that happen afterwards in the same location as the mainshock. Depending on the size of the mainshock, Aftershocks can keep happening for weeks, months, or even years after the mainshock happened. Why do earthquakes happen? Earthquakes happen because all the rocks that make up the earth are full of fractures. On some of the fractures that are known as faults, these rocks slip past each other when the crust rearranges itself in a process known as plate tectonics. But the problem is, rocks don’t slip past each other easily because they are stiff, rough and their under a lot of pressure from rocks around and above them. Because of that, rocks can pull at or push on each other on either side of a fault for long periods of time without moving much at all, which builds up a lot of stress in the rocks. -
Source Parameters of the 1933 Long Beach Earthquake
Bulletin of the Seismological Society of America, Vol. 81, No. 1, pp. 81- 98, February 1991 SOURCE PARAMETERS OF THE 1933 LONG BEACH EARTHQUAKE BY EGILL HAUKSSON AND SUSANNA GROSS ABSTRACT Regional seismographic network and teleseismic data for the 1933 (M L -- 6.3) Long Beach earthquake sequence have been analyzed, Both the teleseismic focal mechanism of the main shock and the distribution of the aftershocks are consistent with the event having occurred on the Newport-lnglewood fault. The focal mechanism had a strike of 315 °, dip of 80 o to the northeast, and rake of - 170°. Relocation of the foreshock- main shock-aftershock sequence using modern events as fixed refer- ence events, shows that the rupture initiated near the Huntington Beach-Newport Beach City boundary and extended unilaterally to the northwest to a distance of 13 to 16 km. The centroidal depth was 10 +_ 2 km. The total source duration was 5 sec, and the seismic moment was 5.102s dyne-cm, which corresponds to an energy magnitude of M w = 6.4. The source radius is estimated to have been 6.6 to 7.9 km, which corresponds to a Brune stress drop of 44 to 76 bars. Both the spatial distribution of aftershocks and inversion for the source time function suggest that the earthquake may have consisted of at least two subevents. When the slip estimate from the seismic moment of 85 to 120 cm is compared with the long-term geological slip rate of 0.1 to 1.0 mm I yr along the Newport-lnglewood fault, the 1933 earthquake has a repeat time on the order of a few thousand years. -
Slow Slip Event on the Southern San Andreas Fault Triggered by the 2017 Mw8.2 Chiapas (Mexico) Earthquake That Occurred 3,000 Km Away
RESEARCH ARTICLE Slow Slip Event On the Southern San Andreas Fault 10.1029/2018JB016765 Triggered by the 2017 Mw8.2 Chiapas (Mexico) Key Points: Earthquake • We present geodetic and geologic observations of slow slip on the 1,2 1 1,3 1 southern SAF triggered by the 2017 Ekaterina Tymofyeyeva , Yuri Fialko , Junle Jiang , Xiaohua Xu , Chiapas (Mexico) earthquake David Sandwell1 , Roger Bilham4 , Thomas K. Rockwell5 , Chelsea Blanton5 , • The slow slip event produced surface 5 5 6 offsets on the order of 5–10 mm, with Faith Burkett ,Allen Gontz , and Shahram Moafipoor significant variations along strike 1 • We interpret the observed complexity Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California San Diego, in shallow fault slip in the context of La Jolla, CA, USA, 2Now at Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA, 3Now at rate-and-state friction models Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, NY, USA, 4CIRES and Geological Sciences, University of Colorado, Boulder, CO, USA, 5Department of Geological Sciences, San Diego State University, San Diego, 6 Supporting Information: CA, USA, Geodetics Inc., San Diego, CA, USA • Supporting Information S1 Abstract Observations of shallow fault creep reveal increasingly complex time-dependent slip Correspondence to: histories that include quasi-steady creep and triggered as well as spontaneous accelerated slip events. Here E. Tymofyeyeva, [email protected] we report a recent slow slip event on the southern San Andreas fault triggered by the 2017 Mw8.2 Chiapas (Mexico) earthquake that occurred 3,000 km away. Geodetic and geologic observations indicate that surface slip on the order of 10 mm occurred on a 40-km-long section of the southern San Andreas fault Citation: Tymofyeyeva, E., Fialko, Y., Jiang, J., between the Mecca Hills and Bombay Beach, starting minutes after the Chiapas earthquake and Xu, X., Sandwell, D., Bilham, R., et al. -
The Megathrust Earthquake Cycle
Ocean. A little less than four years later, a similar-sized earthquake strikes the Prince William Sound area of Alaska producing a tsunami that ravages Alaska and the west coast of North America. At the time, it was clear Not My Fault: The megathrust these were very large quakes, registering 8.6 and 8.5 on earthquake cycle the Surface Wave magnitude scale, the variant of the Lori Dengler/For the Times-Standard Richter scale that was in use at the time. But only after Posted: May 24, 2017 theresearch of two more Reid award winners Aki and Kanamori (whose work would replace the Richter scale The Seismological Society of America is the world’s with seismic moment and moment magnitude) would largest organization dedicated to the study of the true size of these earthquakes Become clear. When earthquakes and their impacts on humans. The recalculated in the 70s, 1964 Alaska was upped to 9.2 Society’s highest honor is the Henry F. Reid Award and 1960 Chile Became a whopping 9.5, the largest recognizes the work that has done the most to the magnitude earthquake ever recorded on a seismograph. transform the discipline. This year’s recipient is George Plafker for his studies of great suBduction zone Both of these earthquakes occurred before plate earthquakes. tectonics, the grand unifying theory of how the outer part of the earth works, was well known or accepted. In I mentioned Dr. Plafker in my last column as a pioneer of the sixties, many earth scientists Believed great post earthquake/tsunami reconnaissance. -
Analyzing the Performance of GPS Data for Earthquake Prediction
remote sensing Article Analyzing the Performance of GPS Data for Earthquake Prediction Valeri Gitis , Alexander Derendyaev * and Konstantin Petrov The Institute for Information Transmission Problems, 127051 Moscow, Russia; [email protected] (V.G.); [email protected] (K.P.) * Correspondence: [email protected]; Tel.: +7-495-6995096 Abstract: The results of earthquake prediction largely depend on the quality of data and the methods of their joint processing. At present, for a number of regions, it is possible, in addition to data from earthquake catalogs, to use space geodesy data obtained with the help of GPS. The purpose of our study is to evaluate the efficiency of using the time series of displacements of the Earth’s surface according to GPS data for the systematic prediction of earthquakes. The criterion of efficiency is the probability of successful prediction of an earthquake with a limited size of the alarm zone. We use a machine learning method, namely the method of the minimum area of alarm, to predict earthquakes with a magnitude greater than 6.0 and a hypocenter depth of up to 60 km, which occurred from 2016 to 2020 in Japan, and earthquakes with a magnitude greater than 5.5. and a hypocenter depth of up to 60 km, which happened from 2013 to 2020 in California. For each region, we compare the following results: random forecast of earthquakes, forecast obtained with the field of spatial density of earthquake epicenters, forecast obtained with spatio-temporal fields based on GPS data, based on seismological data, and based on combined GPS data and seismological data. -
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. -
Drilling Into Shallow Interplate Thrust Zone for Understanding of Irregular Rupturing of Megathrust
Drilling into shallow interplate thrust zone for understanding of irregular rupturing of megathrust Ryota Hino (Tohoku University) * abstract It is generally conceived that the shallowest portion of the megathrsut fault is completely aseismic and allow stable sliding during the interseismic period. However, anomalous tsunami earthquakes sporadically happen in this area, causing disproportionally large tsunami as compared to the radiated seismic energy, release large displacement at the plate boundary. It has not been well understood why and how such the anomalous earthquake occurs irregularly. Also in the rupture propagation of gigantic (M>9) earthquakes involving simultaneous rupturing of multiple asperities, the aseismic plate boundary seems to play an important role. Therefore, the mechanical properties of the most trenchward zone of the subudction plate boundary are very important for understanding mechanisms generating catastrophic earthquakes. I propose here to make long-term monitoring in deep boreholes drilled the shallowest portion of the megathrust fault to clarify how deform this area in the interseismic period. Downhole logging and seismic profiling will provide the answer to the cause of the anomalous rupture process by revealing the internal structure of the fault zone. * Research center for prediction of earthquakes and volcanic eruption Graduate School of Science, Tohoku University [email protected] 1. Introduction The occurrence of the 2004 Sumatra-Andaman earthquake (M9.1) showed that an interplate earthquake which ruptures almost entire part of a subduction system can occur, although we only know recurrence history of thrust earthquakes with sizes of M~8 in the system. Recent paleoseismological studies have revealed the occurrence of gigathrust earthquakes, much larger than M8 class megathrust earthquakes, in other subduction zones where only megathrust earthquakes have been known to occur.