Subduction Zone Earthquakes Research Articles

Coseismic slip propagation on the Tohoku plate boundary fault facilitated by slip‐dependent weakening during slow fault slip

AbstractSlow slip phenomena, including earthquake afterslip and discrete slow slip events (SSEs), may have a major effect on megathrust earthquakes in subduction zones; however, the nature of this effect is still incompletely understood. Here we report that in friction experiments using samples from the plate boundary fault zone in the 2011 Tohoku‐Oki earthquake, an increase in sliding velocity can induce a change from steady state frictional strength or slip‐strengthening friction to slip‐weakening frictional behavior. Specifically, significant slip weakening is caused by velocity steps with initial slip rates consistent with afterslip observed after the largest Tohoku earthquake foreshock on 9 March 2011. This suggests that the foreshock afterslip, which is slightly faster than discrete SSEs, is favorable for fault weakening that may have contributed to the large coseismic slip during the main shock on the shallow plate boundary fault during the Tohoku‐Oki earthquake.

An Investigation of the Accuracy of Coulomb Stress Changes Inferred From Geodetic Observations Following Subduction Zone Earthquakes

AbstractEarthquake clustering along plate boundaries suggests that earthquakes may interact, and static Coulomb stress change (CSC) is commonly invoked as one possible mechanism for stress transfer between earthquakes and nearby faults. Previous work has addressed the precision of CSC predictions that are influenced by observational noise, inversion regularization, and simplified modeling assumptions. Here we address the accuracy of CSC predictions informed by geodetic observations in subduction zones where inversion model resolution is poor. We conduct synthetic tests to quantify the degree to which the sign and magnitude of CSC can be reliably inferred from slip distributions inverted from various geodetic observations (interferometric synthetic aperture radar (InSAR), GPS, and seafloor observations). We find that in an idealized subduction zone, CSC can only be confidently inferred for receiver faults far (tens of kilometers) from the earthquake source, though this distance shortens with the addition of synthetic seafloor observations. We apply this methodology to the 2010 Mw8.8 Maule earthquake and identify 13 aftershocks from a population of 475 documented events for which we can confidently resolve coseismic stress changes. These results demonstrate that the low model resolution of fault slip inversions in subduction zones limits our ability to address fundamental questions about earthquake sources and stress interactions. Nonetheless, our results highlight that stress change predictions are considerably more accurate after the introduction of seafloor geodetic observations. Additionally, we show that InSAR observations are not required to substantially improve stress change approximations in regions where GPS may be the only viable observation, such as in island arcs settings.

Coastal erosion and recovery from a Cascadia subduction zone earthquake and tsunami

Tsunamis generated by great earthquakes threaten coastal infrastructure, development, and human life. Earlier work has documented the inland extent and frequency of past tsunamis, but little is known about the magnitude of material eroded during prehistoric tsunamis and how erosion and coastal recovery are recorded in coastal stratigraphy. In this study we use high-resolution ground-penetrating radar (GPR) to image and quantify coastal erosion experienced during a late Holocene (~900calBP) Cascadia subduction zone earthquake and tsunami along the northern California coast. The GPR profiles illustrate three stratigraphic signatures created during co-seismic subsidence and tsunami erosion and coastal recovery. The first is erosional truncation of the underlying seaward-dipping reflections created by pre-tsunami normal beach progradation. The second is a series of landward-dipping, flat-lying, and channelized reflections marking the filling of erosional topography and coastal reworking of the irregular shoreline following inundation and erosion. The third is an abrupt landward termination of the stratigraphic unit marking coastal straightening and post-tsunami rejuvenation of normal coastal progradation. Erosion from the ~900calBP earthquake and tsunami extended >110m inland of the contemporary shoreline and removed/reworked 225,000±28,000m3 of sand from a 1.7-km stretch of the coast, far exceeding anything experienced during historical El Niños along the Pacific Coast of North America. This study provides the first quantitative estimate of the amount of coastal erosion from a pre-historic earthquake and tsunami and outlines a strategy for estimating erosion during similar events elsewhere.

Deep postseismic viscoelastic relaxation excited by an intraslab normal fault earthquake in the Chile subduction zone

The 2005 Mw 7.8 Tarapaca earthquake was the result of normal faulting on a west-dipping plane at a depth of ~90km within the subducting slab down-dip of the North Chilean gap that partially ruptured in the 2014 M 8.2 Iquique earthquake. We use Envisat observations of nearly four years of postseismic deformation following the earthquake, together with some survey GPS measurements, to investigate the viscoelastic relaxation response of the surrounding upper mantle to the coseismic stress. We constrain the rheological structure by testing various 3D models, taking into account the vertical and lateral heterogeneities in viscosity that one would expect in a subduction zone environment. A viscosity of 4–8×1018Pas for the continental mantle asthenosphere fits both InSAR line-of-sight (LOS) and GPS horizontal displacements reasonably well. In order to test whether the Tarapaca earthquake and associated postseismic relaxation could have triggered the 2014 Iquique sequence, we computed the Coulomb stress change induced by the co- and postseismic deformation following the Tarapaca earthquake on the megathrust interface and nodal planes of its M 6.7 foreshock. These static stress calculations show that the Tarapaca earthquake may have an indirect influence on the Iquique earthquake, via loading of the M 6.7 preshock positively. We demonstrate the feasibility of using deep intraslab earthquakes to constrain subduction zone rheology. Continuing geodetic observation following the 2014 Iquique earthquake may further validate the rheological parameters obtained here.

Double-ramp on the Main Himalayan Thrust revealed by broadband waveform modeling of the 2015 Gorkha earthquake sequence

The 2015Mw7.8 Gorkha earthquake sequence that unzipped the lower edge of the Main Himalayan Thrust (MHT) in central Nepal provides an exceptional opportunity to understand the fault geometry in this region. However, the limited number of focal mechanisms and the poor horizontal locations and depths of earthquakes in the global catalog impede us from clearly imaging the ruptured MHT. In this study, we generalized the Amplitude Amplification Factor (AAF) method to teleseismic distance that allows us to model the teleseismic P-waves up to 1.5 Hz. We used well-constrained medium-sized earthquakes to establish AAF corrections for teleseismic stations that were later used to invert the high-frequency waveforms of other nearby events. This new approach enables us to invert the focal mechanisms of some early aftershocks, which is challenging by using other long-period methods. With this method, we obtained 12 focal mechanisms more than that in the GCMT catalog. We also modeled the high-frequency teleseismic P-waves and the surface reflection phases (pP and sP) to precisely constrain the depths of the earthquakes. Our results indicate that the uncertainty of the depth estimation is as small as 1–2 km. Finally, we refined the horizontal locations of these aftershocks using carefully hand-picked arrivals. The refined aftershock mechanisms and locations delineate a clear double-ramp geometry of the MHT, with an almost flat décollement sandwiched in between. The flat (dip ∼7 degrees) portion of the MHT is consistent with the coseismic rupture of the mainshock, which has a well-constrained slip distribution. The fault morphology suggests that the ramps, both along the up-dip and down-dip directions, play a significant role in stopping the rupture of the 2015 Gorkha earthquake. Our method can be applied to general subduction zone earthquakes and fault geometry studies.

Ground motion and site effect observations in the wellington region from the 2016 Mw7.8 Kaikōura, New Zealand earthquake

This paper presents ground motion and site effect observations in the greater Wellington region from the 14 November 2016 Mw7.8 Kaikōura earthquake. The region was the principal urban area to be affected by the earthquake-induced ground motions from this event. Despite being approximately 60km from the northern extent of the causative earthquake rupture, the ground motions in Wellington exhibited long period (specifically T = 1 - 3s) ground motion amplitudes that were similar to, and in some locations exceeded, the current 500 year return period design ground motion levels. Several ground motion observations on rock provide significant constraint to understand the role of surficial site effects in the recorded ground motions. The largest long period ground motions were observed in the Thorndon and Te Aro basins in Wellington City, inferred as a result of 1D impedance contrasts and also basin-edge-generated waves. Observed site amplifications, based on response spectral ratios with reference rock sites, are seen to significantly exceed the site class factors in NZS1170.5:2004 for site class C, D, and E sites at approximately T=0.3-3.0s. The 5-95% Significant Duration, Ds595, of ground motions was on the order of 30 seconds, consistent with empirical models for this earthquake magnitude and source-to-site distance. Such durations are slightly longer than the corresponding Ds595 = 10s and 25s in central Christchurch during the 22 February 2011 Mw6.2 and 4 September 2010 Mw7.1 earthquakes, but significantly shorter than what might be expected for large subduction zone earthquakes that pose a hazard to the region. In summary, the observations highlight the need to better understand and quantify basin and near-surface site response effects through more comprehensive models, and better account for such effects through site amplification factors in design standards.

An approach for estimating the largest probable tsunami from far-field subduction zone earthquakes

Following the recent unexpected earthquake events of 2004 and 2011, it can be cautiously extrapolated that all major subduction zones bearing the capacity to produce mega-earthquake events will eventually do so given enough time, irrespective of the lack of such in the relatively short historical record. This notion has led to an effort of assigning maximum earthquake magnitudes to all major subduction zones, either based on geological constraints or based on size–frequency relations, or a combination of both. In this study, we utilize the proposed maximum magnitudes to assess tsunami hazard in Central California in the very long return periods. We also assessed tsunami hazard following an alternative methodology to calculate maximum magnitudes, which uses scaling relations for subduction zone earthquakes and maximum fault rupture scenarios found in literature. A sensitivity analysis is performed for Central California that is applicable to any coastal site in the Pacific Rim and can readily provide a strong indication for which subduction zones beam the most energy toward a study area. The maximum earthquake scenarios are then narrowed down to a few candidates, for which the initial conditions are examined in more detail. The chosen worst-case scenarios for Central California stem from the Alaska–Aleutian subduction zone that beams more energy and generates the biggest amplitude waves toward the study area. The largest tsunami scenario produces maximum free surface elevations of 15 m and run-up heights greater than 20 m.

Agent-based tsunami evacuation modeling of unplanned network disruptions for evidence-driven resource allocation and retrofitting strategies

The M9 Cascadia subduction zone earthquake represents one of the most pressing natural hazard threats in the Pacific Northwest of the USA with an astonishing high 7–12% chance of occurrence by 2060, mirroring the 2011 devastating earthquake and tsunami in Japan. Yet this region, like many other coastal communities, is underprepared, lacking a comprehensive understanding of unplanned network disruptions as a key component to disaster management planning and infrastructure resilience. The goals of this paper are twofold: (1) to conduct a network vulnerability assessment to systematically characterize the importance of each link’s contribution to the overall network resilience, with specific emphasis on identifying the most critical set of links and (2) to create an evidence-driven retrofitting resource allocation framework by quantifying the impacts of unplanned network disruptions to the critical links on network resilience and retrofitting planning. This research used the city of Seaside on the Oregon coast as a study site to create the agent-based tsunami evacuation modeling and simulation platform with an explicit focus on the transportation network. The results indicated that (1) the network bridges are not equally important and some of the critical links are counterintuitive and (2) the diverse ways of spending the limited retrofitting resources can generate dramatically different life safety outcomes. These results strongly suggest that accurate characterization and measurement of infrastructure network failures will provide evidence-driven retrofitting planning strategies and inform resource allocations that enhance network resilience.

Coseismic seafloor deformation in the trench region during the Mw8.8 Maule megathrust earthquake

The Mw 8.8 megathrust earthquake that occurred on 27 February 2010 offshore the Maule region of central Chile triggered a destructive tsunami. Whether the earthquake rupture extended to the shallow part of the plate boundary near the trench remains controversial. The up-dip limit of rupture during large subduction zone earthquakes has important implications for tsunami generation and for the rheological behavior of the sedimentary prism in accretionary margins. However, in general, the slip models derived from tsunami wave modeling and seismological data are poorly constrained by direct seafloor geodetic observations. We difference swath bathymetric data acquired across the trench in 2008, 2011 and 2012 and find ~3–5 m of uplift of the seafloor landward of the deformation front, at the eastern edge of the trench. Modeling suggests this is compatible with slip extending seaward, at least, to within ~6 km of the deformation front. After the Mw 9.0 Tohoku-oki earthquake, this result for the Maule earthquake represents only the second time that repeated bathymetric data has been used to detect the deformation following megathrust earthquakes, providing methodological guidelines for this relatively inexpensive way of obtaining seafloor geodetic data across subduction zone.

Self‐contained local broadband seismogeodetic early warning system: Detection and location

AbstractEarthquake and local tsunami early warning is critical to mitigating adverse impacts of large‐magnitude earthquakes. An optimal system must rely on near‐source data to maximize warning time. To this end, we have developed a self‐contained seismogeodetic early warning system employing an optimal combination of high‐frequency information from strong‐motion accelerometers and low‐frequency information from collocated Global Navigation Satellite Systems (GNSS) instruments to estimate real‐time displacements and velocities. Like GNSS, and unlike broadband seismometers, seismogeodetic stations record the full waveform, including static offset, without clipping in the near‐field or saturating for large magnitude earthquakes. However, GNSS alone cannot provide a self‐contained system and requires an external seismic trigger. Seismogeodetic stations detect P wave arrivals with the same sensitivity as strong‐motion accelerometers and thus provide a stand‐alone system. We demonstrate the utility of near‐source seismogeodesy for event detection and location with analysis of the 2010 Mw7.2 El Mayor‐Cucapah, Baja, California and 2014 Mw6.0 Napa, California strike‐slip events, and the 2014 Mw8.2 Iquique, Chile subduction zone earthquake using observatory‐grade accelerometers and GPS data. We present lessons from the 2014 Mw4.0 Piedmont, California and 2016 Mw5.2 Borrego Springs, California earthquakes, recorded by our seismogeodetic system with Micro‐Electro Mechanical System (MEMS) accelerometers and GPS data and reanalyzed retrospectively. We conclude that our self‐contained seismogeodetic system is suitable for early warning for earthquakes of significance (>M5) using either observatory‐grade or MEMS accelerometers. Finally, we discuss the effect of network design on hypocenter location and suggest the deployment of additional seismogeodetic stations for the western U.S.

Role of H<sub>2</sub>O in Generating Subduction Zone Earthquakes

Role of H<sub>2</sub>O in Generating Subduction Zone Earthquakes

Rupture features of the 2010 Mw 8.8 Chile earthquake extracted from surface waves

This study used the rupture directivity theory to derive the fault parameters of the 2010 Mw 8.8 Chile earthquake on the basis of the azimuth-dependent source duration obtained from the Rayleigh-wave phase velocity. Results revealed that the 2010 Chile earthquake featured asymmetric bilateral faulting. The two rupture directions were N171°E (northward) and N17°E (southward), with rupture lengths of approximately 313 and 118 km, respectively, and were related to the locking degree in the source region. The entire source duration was approximately 187 s. After excluding the rise time from the source duration, the northward rupture velocity was approximately 2.02 km/s, faster than the southward rupture velocity (1.74 km/s). On average, the rupture velocity derived from this study was slower than that estimated from finite-fault inversion; however, several historical earthquakes in the Chile region also showed slow rupture velocity when using low-frequency signals, as surface waves do. Two earlier studies through global-positioning-system data analysis showed that the static stress drop of 50–70 bars for the 2010 Chile earthquake was higher than that for subduction-zone earthquakes. Hence, a remarkable feature was that the 2010 Chile earthquake had a slow rupture velocity and a high static stress drop, which suggested an inverse relationship between rupture velocity and static stress drop.Graphical abstract.

Projecting community changes in hazard exposure to support long-term risk reduction: A case study of tsunami hazards in the U.S. Pacific Northwest

Tsunamis have the potential to cause considerable damage to communities along the U.S. Pacific Northwest coastline. As coastal communities expand over time, the potential societal impact of tsunami inundation changes. To understand how community exposure to tsunami hazards may change in coming decades, we projected future development (i.e. urban, residential, and rural), households, and residents over a 50-year period (2011–2061) along the Washington, Oregon, and northern California coasts. We created a spatially explicit, land use/land cover, state-and-transition simulation model to project future developed land use based on historical development trends. We then compared our development projection results to tsunami-hazard zones associated with a Cascadia subduction zone (CSZ) earthquake. Changes in tsunami-hazard exposure by 2061 were estimated for 50 incorporated cities, 7 tribal reservations, and 17 counties relative to current (2011) estimates. Across the region, 2061 population exposure in tsunami-hazard zones was projected to increase by 3880 households and 6940 residents. The top ten communities with highest population exposure to CSZ-related tsunamis in 2011 are projected to remain the areas with the highest population exposure by 2061. The largest net population increases in tsunami-hazard zones were projected in the unincorporated portions of several counties, including Skagit, Coos, and Humboldt. Land-change simulation modeling of projected future development serves as an exploratory tool aimed at helping local governments understand the hazard-exposure implications of community growth and to include this knowledge in risk-reduction planning.

Empirical Attenuation relationship for Peak Ground Horizontal Acceleration for North-East Himalaya

Empirical Attenuation relationship for Peak Ground Horizontal Acceleration for North-East Himalaya

Ground Motion Prediction Equations for Malaysia Due to Subduction Zone Earthquakes in Sumatran Region

There has been numerous seismic hazard studies so far that includes Malaysian territories. However, there is a need to assess how reliable those studies are. Two main potential contributors to error have been identified: 1) seismic hazard analysis method and 2) ground motion prediction equation (GMPE). The amount of variation in predicting erroneous GMPE is huge. Thus, this paper concentrates on generating new GMPEs due to subduction specified for Malaysia and validated against developed GMPE. Empirical method for GMPE generation was utilized using recorded ground motion data acquired from the Malaysian Meteorological Department. The earthquakes were grouped according to the source, and only source types in the Sumatran subduction area were used due to the availability of enough data to identify a pattern. Three GMPEs were generated for three different source types, namely, shallow subduction earthquake, deep subduction earthquake, and backarc earthquake sources. Sumatran strike slip fault is considered within backarc seismicity. They were compared with the models proposed by Petersen (modified from Young), Atkinson and Boore, and Megawati. The comparison results showed that the proposed models are far superior at predicting the earthquakes in the Sumatran region, with percentage difference between estimates and the recorded values being the lowest. Therefore, the equations should be used in further seismic hazard analyses. Thus, this paper becomes a part of the recent initiatives in Malaysia to assess the hazards posed by earthquakes.

Ground motion prediction equations for the Chilean subduction zone

The Chilean subduction zone is one of the most active in the world. Six events of magnitude greater than \(M_w = 7.5\) have occurred in the last 10 years, including the 2010 \(M_w = 8.8\) Maule, the 2014 \(M_w = 8.2\) Iquique, and the 2015 \(M_w = 8.3\) Illapel earthquakes. These events have produced a considerable dataset to study interface thrust and intraslab intermediate depth earthquakes. In this paper, we present a database of strong motion records for Chilean subduction zone earthquakes and develop a ground motion prediction equation (GMPE) for peak ground acceleration and response spectral accelerations with 5% damping ratio for periods between 0.01 and 10 s. The dynamic soil amplification effects are considered in a new empirical model based on two parameters, the predominant period of the soil (\(T^*\)) and the average shear wave velocity down to 30 m depth (\(V_{S30}\)). The spectral accelerations prediction equations at short periods are generated using 114 records of intraslab earthquakes (\(M_w\) = 5.5–7.8) and 369 records of interface earthquakes (\(M_w\) = 5.5–8.8); a reduced number of these records are used for longer periods. The proposed GMPE can predict the ground motion of large Chilean subduction earthquakes (\(M_w > 8\)) with no need of extrapolation from small-magnitude earthquake data. Intraslab earthquakes show a steeper attenuation slope than that of interface ones, which is consistent with other GMPE results derived from worldwide subduction zones data. Moreover, the Chilean interface earthquakes show a flatter attenuation slope relative to the Japanese ones.

Extreme tsunami inundation in Hawai\u2018i from Aleutian\u2013Alaska subduction zone earthquakes

The 2011 Tohoku earthquake and tsunami motivated an analysis of the potential for great tsunamis in Hawai‘i that significantly exceed the historical record. The largest potential tsunamis that may impact the state from distant, Mw 9 earthquakes—as forecast by two independent tsunami models—originate in the Eastern Aleutian Islands. This analysis is the basis for creating an extreme tsunami evacuation zone, updating prior zones based only on historical tsunami inundation. We first validate the methodology by corroborating that the largest historical tsunami in 1946 is consistent with the seismologically determined earthquake source and observed historical tsunami amplitudes in Hawai‘i. Using prior source characteristics of Mw 9 earthquakes (fault area, slip, and distribution), we analyze parametrically the range of Aleutian–Alaska earthquake sources that produce the most extreme tsunami events in Hawai‘i. Key findings include: (1) An Mw 8.6 ± 0.1 1946 Aleutian earthquake source fits Hawai‘i tsunami run-up/inundation observations, (2) for the 40 scenarios considered here, maximal tsunami inundations everywhere in the Hawaiian Islands cannot be generated by a single large earthquake, (3) depending on location, the largest inundations may occur for either earthquakes with the largest slip at the trench, or those with broad faulting over an extended area, (4) these extremes are shown to correlate with the frequency content (wavelength) of the tsunami, (5) highly variable slip along the fault strike has only a minor influence on inundation at these tele-tsunami distances, and (6) for a given maximum average fault slip, increasing the fault area does not generally produce greater run-up, as the additional wave energy enhances longer wavelengths, with a modest effect on inundation.

The effect of compliant prisms on subduction zone earthquakes and tsunamis

Earthquakes generate tsunamis by coseismically deforming the seafloor, and that deformation is largely controlled by the shallow rupture process. Therefore, in order to better understand how earthquakes generate tsunamis, one must consider the material structure and frictional properties of the shallowest part of the subduction zone, where ruptures often encounter compliant sedimentary prisms. Compliant prisms have been associated with enhanced shallow slip, seafloor deformation, and tsunami heights, particularly in the context of tsunami earthquakes. To rigorously quantify the role compliant prisms play in generating tsunamis, we perform a series of numerical simulations that directly couple dynamic rupture on a dipping thrust fault to the elastodynamic response of the Earth and the acoustic response of the ocean. Gravity is included in our simulations in the context of a linearized Eulerian description of the ocean, which allows us to model tsunami generation and propagation, including dispersion and related nonhydrostatic effects. Our simulations span a three-dimensional parameter space of prism size, prism compliance, and sub-prism friction – specifically, the rate-and-state parameter b−a that determines velocity-weakening or velocity-strengthening behavior. We find that compliant prisms generally slow rupture velocity and, for larger prisms, generate tsunamis more efficiently than subduction zones without prisms. In most but not all cases, larger, more compliant prisms cause greater amounts of shallow slip and larger tsunamis. Furthermore, shallow friction is also quite important in determining overall slip; increasing sub-prism b−a enhances slip everywhere along the fault. Counterintuitively, we find that in simulations with large prisms and velocity-strengthening friction at the base of the prism, increasing prism compliance reduces rather than enhances shallow slip and tsunami wave height.

Fault zone controlled seafloor methane seepage in the rupture area of the 2010 Maule earthquake, Central Chile

AbstractSeafloor seepage of hydrocarbon‐bearing fluids has been identified in a number of marine fore arcs. However, temporal variations in seep activity and the structural and tectonic parameters that control the seepage often remain poorly constrained. Subduction zone earthquakes, for example, are often discussed to trigger seafloor seepage but causal links that go beyond theoretical considerations have not yet been fully established. This is mainly due to the inaccessibility of offshore epicentral areas, the infrequent occurrence of large earthquakes, and challenges associated with offshore monitoring of seepage over large areas and sufficient time periods. Here we report visual, geochemical, geophysical, and modeling results and observations from the Concepción Methane Seep Area (offshore Central Chile) located in the rupture area of the 2010 Mw. 8.8 Maule earthquake. High methane concentrations in the oceanic water column and a shallow subbottom depth of sulfate penetration indicate active methane seepage. The stable carbon isotope signature of the methane and hydrocarbon composition of the released gas indicate a mixture of shallow‐sourced biogenic gas and a deeper sourced thermogenic component. Pristine fissures and fractures observed at the seafloor together with seismically imaged large faults in the marine fore arc may represent effective pathways for methane migration. Upper plate fault activity with hydraulic fracturing and dilation is in line with increased normal Coulomb stress during large plate‐boundary earthquakes, as exemplarily modeled for the 2010 earthquake. On a global perspective our results point out the possible role of recurring large subduction zone earthquakes in driving hydrocarbon seepage from marine fore arcs over long timescales.

Reply to “Comment on ‘Statistical Analyses of Great Earthquake Recurrence along the Cascadia Subduction Zone’ by Ram Kulkarni, Ivan Wong, Judith Zachariasen, Chris Goldfinger, and Martin Lawrence” by Allan Goddard Lindh

In our article Kulkarni et al. (2013), we favored a clustered model for great Cascadia subduction zone (CSZ) earthquakes and our statistical analysis resulted in a probability of 0.65 that clustering was present in the turbidite record. The CSZ clustering analysis was originally motivated by the need to develop a CSZ logic tree for use in probabilistic seismic‐hazard analysis. In recognition of the two principal models that could explain the pattern of great earthquake occurrence observed in the turbidite record, we gave weights of 0.65 and 0.35 to clustered versus quasi‐periodic behavior in the logic tree, respectively (Wong et al. , 2014). In Lindh (2016), Al Lindh questioned the validity of the turbidite data and our analysis of temporal clustering and states that the CSZ actually behaves in a quasi‐periodic behavior. He summarizes his argument in four points, and we wish to respond to each point in the following. We confine our responses to the technical issues raised by Lindh. With regards to his discussion on seismic risk in the Pacific Northwest, we support his views. Certainly, understanding the behavior of the CSZ, particularly its recurrence, is a critical element in earthquake‐risk reduction in the Pacific Northwest. We appreciate Lindh for pointing out the more recent studies that indicate that for a few of the examples we cited, clustering of full‐rupture earthquakes may not be characteristic of the behavior that was previously suggested. However, the point we were trying to make is that earthquake clustering, regardless of scale or magnitude, is a behavior that is observed along plate boundaries and crustal faults worldwide. There are physical models that can explain temporal clustering, and the quasi‐periodic behavior favored by Lindh is unusual over long time spans. Many factors can come into play that can alter the long‐term behavior of a …