Intraplate Stress Field Research Articles

The Intraplate Stress Field of West Africa

AbstractWest Africa continues to host a growing number of low and intermediate‐magnitude earthquakes (M2‐5) along its passive margins, and its continental interior. Earthquake activity in these regions raises the need to comprehend the causes and the tectonic controls of the seismicity. Unfortunately, such studies are rare. Here, we apply single‐station inversion techniques to constrain fourteen focal mechanisms, computed after compiling a set of high‐quality waveforms. We describe the connection between seismicity, the contemporary stress field, anthropogenic activity and Holocene fault scarps in the region. Our results indicate transpressive stresses acting on the inherited brittle structures in the passive margins. We also observe a compressive regime in the intracontinental failed rifts. We attribute the seismicity to the reactivation of “weak” faults in the Neoproterozoic and Mesozoic failed rifts, the passive transform structures, and the intracratonic Precambrian brittle shear zones.

The 4.5 mb Amargosa earthquake of 30 August 2020, Bahia, Brazil: Implications for the intraplate stress field across the continental margin

The 4.5 mb Amargosa earthquake was the largest event to occur in the state of Bahia, NE Brazil, in more than 100 years. It caused intensity VI MM in the epicentral area and was felt up to more than 200 km away. A previously published focal mechanism determination had suggested a normal faulting event at about 10 km depth. However, our detailed analyses of regional and teleseismic records show, in fact, a reverse faulting mechanism and a very shallow depth of about 1 km. The shallow hypocentral depth was consistently determined by modeling of teleseismic P waves, as well as waveform inversion of regional stations for moment tensor solution. Our focal mechanism solution is also consistent with the relative location of the aftershocks which shows the fault plane to be oriented ESE-WNW dipping to the SSW. The P axis is oriented about NNE-SSW, parallel to the coast. In the interior of the continent, the maximum horizontal stresses tend to be roughly E-W oriented. The margin parallel P axis of the Amargosa earthquake is similar to other SHmax estimates from breakout data in the marginal basins and is yet another example of stress rotation due to local effects associated with the continental/oceanic crustal transition.

Cenozoic tectonic reactivation and its implications for landscape transience in southeastern Brazil

AbstractIntraplate settings far from tectonic plate boundaries are normally thought to be tectonically inactive regions in which the landscape evolves via the slow downcutting of fluvial systems. When identified, tectonic reactivations are thought to be of too low an amplitude and not cause any change in the landscape. However, in the absence of datable markers of tectonic deformation, the landscape can be used as a passive marker of intraplate tectonic activity. In this study, we investigate the northern boundary of the Ponta Grossa Arch in the southeastern portion of the Brazilian passive margin. We mapped and studied the spatial and temporal (relative) relationships between brittle structures and geomorphic markers of base level changes. Drainage anomalies (knickpoints and high ksn values) are correlated with structural/tectonic lineaments in which we recognize strike‐slip and transtensional faults with right‐lateral and left‐lateral kinematics. Through mapping and analysis of structural data, we constrained the underlying structural framework. The fault data demonstrate the counterclockwise rotation of the maximum stress field, which moved from the NE–SW orientation (at the Cretaceous‐Paleogene boundary) to N‐S to reach the current WNW‐ESE position. Together, the data suggest that, though subtle and low‐magnitude, the evolution of intraplate stress field forms a dynamic forcing of intracontinental landscape change.

Stress State of the Stable Part of the Pacific Plate Predicted by a Numerical Model of Global Mantle Flow Coupled with Plate Motion

Abstract The Pacific plate, which is the largest oceanic plate on Earth, has implications for the general understanding of plate dynamics, including the origin of intraplate stress and the driving force for plate motion. However, this is currently limited by the scarcity of geophysical and geological observational data. In this study, an instantaneous global mantle flow calculation was performed to predict the intraplate stress field and stress regimes on the Pacific plate using a geodynamic model based on the density anomaly structure of the mantle converted from a seismic tomography model incorporating subducting plates. The numerical results demonstrate that the southern part of the Pacific plate is dominated by a normal faulting regime. In contrast, the northern part is dominated by a thrust faulting regime, in which the tensional stress axes in the older and stable part of the Pacific plate tend to be oblique to the direction of plate motion. This suggests that the stress state of the Pacific plate is almost neutral (i.e., neither compressional nor tensional) along the direction of plate motion. Furthermore, shallow positive buoyancy-induced asthenospheric flow is essential for reproducing the observed plate motion of the Pacific plate.

Basement Structure and Styles of Active Tectonic Deformation in Central Interior Alaska

Central Interior Alaska is one of the most seismically active regions in North America, exhibiting a high concentration of intraplate earthquakes approximately 700 km away from the southern Alaska subduction zone. Seismological evidence suggests that intraplate seismicity in the region is not uniformly distributed, but concentrated in several discrete seismic zones, including the Nenana basin and the adjacent Tanana basin. Although the location and magnitude of the seismic activity in both basins are well defined by a network of seismic stations in the region, the tectonic controls on these intraplate earthquakes and the heterogeneous nature of Alaska’s continental interior remain poorly understood. We investigated the crustal structure of the Nenana and Tanana basins using available seismic reflection, aeromagnetic and gravity anomaly data, supplemented by geophysical well logs and outcrop data. We developed nine new two-dimensional forward models to delineate internal geometries and the crustal structure of Alaska’s interior. The results of our study demonstrates a strong crustal heterogeneity beneath both basins. The Tanana basin is a relatively shallow (up to 2 km) asymmetrical foreland basin with its southern, deeper side controlled by the northern foothills of the Central Alaska Range. Northeast-trending left lateral strike-slip faults within the Tanana basin are interpreted as a zone of clockwise crustal block rotation. The Nenana basin has a fundamentally different geometry. It is a deep (up to 8 km), narrow transtensional pull-apart basin that is deforming along the left-lateral Minto Fault. This study identifies two distinct modes of current tectonic deformation in Central Interior Alaska and provides a basis for modeling the interplay between intraplate stress fields and major structural features that potentially influence the generation of intraplate earthquakes in the region.

Spatiotemporal patterns of the 2020 Haenam earthquake sequence, South Korea: lineament and migration implying fluid-driven earthquake swarm

From late April 2020, 71 consecutive earthquakes with low magnitudes (the largest, Mw 3.2) were catalogued in the county of Haenam, South Korea. In this region, moderate to strong earthquakes were not reported by instrumental, historical, and geological records. We identified 155 uncatalogued events in the source region that occurred between April 25, 2020 and May 8, 2020 and determined the hypocenters of the 226 catalogued and detected events with relative meter-scale location errors based on the cross-correlation approach with data from permanent seismic networks. The clear lineament of the hypocenter distribution defines the fault plane as being 0.3 km by 0.3 km at a depth of ∼20 km, trending WNW-ESE with a dip of ∼70° in the SSW direction. The retrieved moment tensor of the largest event presents a strike of 98°, a dip of 65°, and a rake of 7°, which is close to the inferred fault geometry from relocation results. The hypocenters of the earthquake sequence progressed toward the upper east along the fault-strike direction until the largest event occurred on May 3, 2020 with left-lateral strike-slip motion at the shallower part of the fault plane where the migration is headed. We discuss potential mechanisms that cause non-volcanic earthquake swarms and suggest that the spreading of fluid flow induced the migratory behavior of the Haenam earthquake sequence. This conception of a fluid-driven earthquake swarm is supported by the presence of a seismic migration front that is comparable to a hydraulic diffusivity of 0.012 m2/s in conjunction with inherited WNW-ESE structural sets showing a fault-fracture mesh geometry that can channel the fluid flow. The final part of the sequence forming boundary of the hypocenter distribution could be interpreted as the possible fault-valve behavior at the western end and the permeability barrier at the eastern end, respectively. Our spatiotemporal patterns of the 2020 Haenam earthquake sequence are valuable for understanding earthquake swarms in intraplate stress fields.

Surface Motions and Continental Deformation in the Indian Plate and the India‐Eurasia Collision Zone

AbstractThe collision of the Indian plate with Eurasia has played a major role in controlling the dynamics of central Asia leading to the world's largest continental deformation zone. In order to study the deformation within the Indian plate as well as the India‐Eurasia collision zone, we model the lithospheric stress field by calculating the two primary sources of stress, one arising due to topography and shallow lithospheric structure estimated by gravitational potential energy differences and the other arising from basal tractions derived from density‐driven mantle convection. We use several tomography models to calculate horizontal tractions using the convection code HC for two radially varying viscosity structures. We also take into account lateral viscosity variations in the lithosphere model arising from stiff cratons, weak plate boundaries, and strength variations due to old and young oceanic lithosphere. We do a quantitative comparison of our predicted deviatoric stresses, strain rates, and plate velocities with surface observables and find that the regional tomography model of Singh et al. (2014) embedded in the global S wave model S40RTS does a remarkable job of fitting the observations of GPS velocities and strain rates as well as intraplate stress field from the World Stress Map.

Insights Into Intraplate Stresses and Geomorphology in the Southeastern United States

AbstractThe stress field in the eastern United States is commonly considered to be broadly uniform and due to homogeneous far‐field forces; however, modern and geologic stress indicators in this region show substantial heterogeneity. Using CitcomS to model stresses based on simple input density, temperature, and viscosity fields, we show that local isostasy is key in explaining the intraplate stress field in the southeastern United States. Crustal thickness variations appear to be most important in reproducing observations, although we slightly better match the observed stress field by including variable crustal viscosity informed by magnetotelluric imaging. Our results demonstrate that local gravitational body forces can substantially reorient far‐field stresses and thereby influence patterns of intraplate seismicity. We also show that variable crustal viscosity encourages a steepening of isostatic topography in the southeastern United States; this observation suggests that a sharp boundary in crustal strength may be important in explaining the apparently long‐lived Appalachian topographic escarpment.

Stress reconstruction and lithosphere dynamics along the Sumatra subduction margin

Gravity modeling and stress reconstructions over the Sumatra subduction margin between Indian-Australian and Asian plates provide insights into the geodynamic setting and kinematics of the area. Based on ridge-trench interaction, plate obliquity, plate age and seismicity, the area was divided into two sectors (northern and southern) for gravity modeling along two profiles. The stress data with magnitude Mw ≥ 5.0 and focal depth ≤ 100 km for the subducting plate were compiled for six zones (I–VI), and were isolated under different time-domains for high-resolution study. The reconstructed gravity models were used to isolate the events for subducting (oceanic/Indian-Australian) and overriding (continental/Asian) plates. The data sets for the subducting lithosphere were used for stress inversion to determine the predominant stress regimes for pre-earthquake and post-earthquake phases of the Sumatra earthquake of December 2004. The results were interpreted in terms of operative intra-plate stress fields, and for reconstruction of kinematics and dynamics along the Sumatra subduction margin. Analysis shows both sparse and intense seismic activities identified over different time-segments in the six zones under pre- and post-December 2004 phases with respect to the incidence of Mw 9.2 off Sumatra mega-earthquake of 2004. The stress regime of the 2004 mega-event and subsequent release of strain energy through cyclic changes of the stress obliquities in the northern part of the study area account for heterogeneous coupling caused by rough topography of the subducting Indian-Australian plate. Reduction of compressive stress regime in the deeper segment of the subducting plate in the northern sector triggered twin great strike-slip dominated earthquakes in 2012 in the floor of the northeastern Indian Ocean. The weak zones of a spreading ridge subducting below the Asian plate possibly suffered strain localization and weakening. The less transmission of co- and post-seismic strain energy from northern to southern part of the margin was possibly prohibited near the zone of ridge trench interaction. The trench-orthogonal tearing (slab window) at the edge of the subducting plate in this area cannot be ruled out. The slab window, caused by the subduction of the young buoyant ridge and the trench-ward movement of the upper plate, has transformed the central segment into compressional regime.

Numerical simulation of present day tectonic stress across the Indian subcontinent

In situ measurements of maximum horizontal stress (SHmax) in the Indian subcontinent are limited and do not present regional trends of intraplate stress orientation. The observed orientations of SHmax vary considerably and often differ from the plate velocity direction. We have simulated orientation and magnitude of SHmax through finite element modeling incorporating heterogeneities in elastic property of the Indian continent and plain stress approximation to understand the variability of SHmax. Four different scenarios are tested in simulation: (1) homogeneous plate with fixed plate boundary (2) homogeneous plate with boundary forces (3) heterogeneous plate with fixed boundary (4) heterogeneous plate with boundary forces. The estimated orientation and magnitude of SHmax with a heterogeneous plate with boundary forces in the Himalayan region and an eastern plate boundary comprising the Indo-Burmese arc and Andaman subduction zone are consistent with measured maximum horizontal stress. This study suggests that plate boundary force varies along the northern Indian plate margin and also provides a constraint on the intraplate stress field in the Indian subcontinent.

Lithosphere erosion and continental breakup: Interaction of extension, plume upwelling and melting

We present the results of thermo-mechanical modelling of extension and breakup of a heterogeneous continental lithosphere, subjected to plume impingement in presence of intraplate stress field. We incorporate partial melting of the extending lithosphere, underlying upper mantle and plume, caused by pressure–temperature variations during the thermo-mechanical evolution of the conjugate passive margin system. Effects of melting included in the model account for thermal effects, causing viscosity reduction due to host rock heating, and mechanical effects, due to cohesion loss. Our study provides better understanding on how presence of melts can influence the evolution of rifting. Here we focus particularly on the role of melting for the temporal and spatial evolution of passive margin geometry and rift migration. Depending on the lithospheric structure, melt presence may have a significant impact on the characteristics of areas affected by lithospheric extension. Pre-existing lithosphere heterogeneities determine the location of initial breakup, but in presence of plumes the subsequent evolution is more difficult to predict. For small distances between plume and area of initial rifting, the development of symmetric passive margins is favored, whereas increasing the distance promotes asymmetry. For a plume-rifting distance large enough to prevent interaction, the effect of plumes on the overlying lithosphere is negligible and the rift persists at the location of the initial lithospheric weakness. When the melt effect is included, the development of asymmetric passive continental margins is fostered. In this case, melt-induced lithospheric weakening may be strong enough to cause rift jumps toward the plume location.

Future intraplate stress and the longevity of carbon storage

Carbon capture and storage (CCS) is regarded as a promising strategy for mitigating global warming. A 19% CCS contribution to CO2 reduction by 2050, as envisaged by the International Energy Agency, would require the construction of thousands of CCS sites by the 2030s and beyond. CO2 storage may need to last for tens of thousands of years to avoid potential global warming and major Earth system changes, and a critical site selection criterion will be the likelihood of future escape of stored CO2 due to fault reactivation. However, future long-term intraplate stress field changes have not been considered in this context. Here we focus on Australia, where 61 potential CCS sites have been proposed, and model the evolving intraplate stress field due to the future growth of tectonic collisional forces north of Australia. Counter intuitively, the largest changes are predicted for some parts of western, central and southeast Australia, all regions far away from plate boundaries, reflecting the non-linear interaction of plate boundary forces with a geologically heterogeneous continent. We suggest that at least ten suggested CCS sites are located in regions where major changes of in situ stress regimes can be expected in the next 100,000years, requiring a careful evaluation of potential future fault reactivation and a breach of reservoir seals. Our results highlight the importance of considering future intraplate stress field changes for selecting CCS sites, particularly within continental regions affected by ongoing mountain building processes including Australia, India, South America, Asia and southern Europe.

State of stress in Texas: Implications for induced seismicity

AbstractCompilation of almost 200 new maximum horizontal stress (SHmax) orientations in Texas reveals a complex intraplate stress field. A large extensional stress province is associated with extensive growth faulting from northeastern Mexico to Louisiana. SHmax is subparallel to the coastline, following the strikes of the growth faults. In contrast, we observe a strike‐slip/normal faulting regime with SHmax approximately E‐W in much of west Texas and the Texas Panhandle, similar to the stress fields observed in northeast New Mexico and north‐central Oklahoma. Within the Fort Worth Basin in northeast Texas, SHmax is NNE‐SSW. The faulting regime transitions from strike‐slip/normal faulting in the northern part of the basin to normal faulting with subequal horizontal principal stress magnitudes further south. Recent sites of apparently injection‐related seismicity near Snyder/Cogdell (west Texas), Karnes City/Fashing (south Texas), the Dallas‐Fort Worth metroplex, and Timpson (east Texas) involves fault slip compatible with local stress fields.

Intraplate stress field in South America from earthquake focal mechanisms

We present an updated compilation of earthquake focal mechanisms in Brazil together with focal mechanisms from the sub-Andean region (mainly from global CMT catalogs). All earthquakes in the sub-Andean region show reverse (majority) or strike-slip faulting mechanisms. Focal mechanisms in Brazil show reverse, strike-slip and normal faulting. Focal mechanisms of nearby earthquakes in the same tectonic environment were grouped and inverted for the stress tensor. In the sub-Andean region, stresses are compressional, as expected, with the principal major compression (S1) roughly E-W, on average. A slight rotation of S1 can be observed and is controlled by the orientation of the Andean plateau. In the sub-Andean region, the intermediate principal stress (S2) is also compressional (i.e., larger than the lithostatic pressure, Sv), a feature that is not always reproduced in numerical models published in the literature. In mid-plate South America stresses seem to vary in nature and orientation. In SE Brazil and the Chaco-Pantanal basins, S1 tends to be oriented roughly E-W with S2 approximately equal to S3. This stress pattern changes to purely compressional (both SHmax and Shmin larger than Sv) in the São Francisco craton. A rotation of SHmax from E-W to SE-NW is suggested towards the Amazon region. Along the Atlantic margin, the regional stresses are very much affected by coastal effects (due to continent/ocean spreading stresses as well as flexural effects from sediment load at the continental margin). This coastal effect tends to make SHmax parallel to the coastline and Shmin (usually S3) perpendicular to the coastline. Few breakout data and in-situ measurements are available in Brazil and are generally consistent with the pattern derived from the earthquake focal mechanisms. Although numerical models of global lithospheric stresses tend to reproduce the main large-scale features in most mid-plate areas, the S1 rotation from ∼E-W in SE Brazil to SE-NW in the Amazon region are not well explained by the current numerical models. This means that the observed stress pattern in mid-plate South America should provide new insights into upper mantle dynamics, distinct from current global convection models.

The Late Oligocene to Early Miocene early evolution of rifting in the southwestern part of the Roer Valley Graben

The Roer Valley Graben is a Mesozoic continental rift basin that was reactivated during the Late Oligocene. The study area is located in the graben area of the southwestern part of the Roer Valley Graben. Rifting initiated in the study area with the development of a large number of faults in the prerift strata. Some of these faults were rooted in preexisting zones of weakness in the Mesozoic strata. Early in the Late Oligocene, several faults died out in the study area as strain became focused upon others, some of which were able to link into several-kilometer-long systems. Within the Late Oligocene to Early Miocene northwestward prograding shallow marine syn-rift deposits, the number of active faults further decreased with time. A relatively strong decrease was observed around the Oligocene/Miocene boundary and represents a further focus of strain onto the long fault systems. Miocene extensional strain was not accommodated by further growth, but predominantly by displacements along the long fault systems. Since the Oligocene/Miocene boundary coincides with a radical change in the European intraplate stress field, the latter might have contributed significantly to the simultaneous change of fault kinematics in the study area.

The Paleocene stratigraphic records in the Central Netherlands and close surrounding basins: Highlighting the different responses to a late Danian change in stress regime within the Central European Basin System

Despite their similar structural style of inversion under Late Cretaceous compressional stress, basins in the Central European Basin System showed different kinematic responses to a late Danian change in the European intra-plate stress-field.The Late Cretaceous phase was recognized throughout the Central European Basin System by compressional inversion of the Mesozoic rifts, and the simultaneous formation of marginal troughs. The late Danian change in stress regime resulted in a Middle Paleocene phase which excited longer wavelength of vertical surface movements. In several basins in Central Europe, this Middle Paleocene phase was characterized by domal uplift of the Late Cretaceous inversion zones and their proximal areas, which was interpreted to result from a sudden relaxation of the in-plane tectonic stress (a so-called relaxation inversion).Based on the Paleocene stratigraphic records, this study shows that some basins in the south-western part of the Central European Basin System experienced subsidence of the Late Cretaceous inversion zones during the Middle Paleocene phase, or the complete opposite vertical surface movements of a relaxation inversion. Two possible mechanisms (superposition of relaxation inversions and lithospheric folding during compression) are discussed that could provide an explanation for the opposite late Danian and Selandian vertical surface movements of nearby basins in the Central European Basin System.

The late Maastrichtian to Late Paleocene tectonic evolution of the southern part of the Roer Valley Graben (Belgium)

AbstractThe late Maastrichtian to Late Paleocene seismostratigraphic record of the Roer Valley Graben provides new data on the timing and dynamics of stress changes related to the intra-plate deformation of northwestern Europe. During the deposition of late Maastrichtian to middle Danian limestones, no severe tectonic movements occurred in the southern part of the Roer Valley Graben. Around the late Danian, a known fundamental change in the European intra-plate stress field initiated an increase in subsidence of the southern part of the Roer Valley Graben. Subsidence along the graben border zone enabled relatively thick accumulations of the latest Danian to mid-Selandian siliciclastics in the intra-graben zone. Subsidence was not bounded by large offsets along faults, but rather by flexuring within and along the borders of the Roer Valley Graben. The intensity of these dynamics diminished after the middle Selandian. Most likely due to inherited intra-basinal structural differences, the northern and southern part of the Roer Valley Graben experienced distinctly different late Maastrichtian to Late Paleocene tectonics.

Cenozoic deformation in the Otway Basin, southern Australian margin: implications for the origin and nature of post‐breakup compression at rifted margins

AbstractThere is growing recognition that pulses of compressive tectonic structuring punctuate the post‐breakup subsidence histories of many ‘passive’ rifted continental margins. To obtain new insights into the nature and origin of compression at passive margins, we have conducted a comprehensive analysis of the post‐breakup (<43 Ma) deformation history of the offshore Otway Basin, southern Australian margin, using a regional seismic database tied to multiple wells. Through mapping of a number of regional intra‐Cenozoic unconformities we have determined growth chronologies for a number of major anticlinal structures, most of which are ˜NE–SW‐trending folds that developed during mild inversion of syn‐rift normal faults or through buckling of the post‐rift succession. These chronologies are supplemented by onshore structural evidence and by thermochronological data from key wells. Whilst our analysis confirms the occurrence of a well‐documented pulse of late Miocene–early Pliocene compression, post‐breakup deformation is not restricted to this time interval. We highlight the growth of a number of structures during the mid‐late Eocene and the Oligocene‐early Miocene, with evidence for considerable temporal and spatial migration of strain within the basin. Our results indicate a long‐lived ˜NW–SE maximum horizontal stress orientation since the mid‐late Eocene, consistent with contemporary stress observations but at variance with previous suggestions that this stress orientation was initiated in the late Miocene by increased coupling of the Australian‐Pacific plate boundary. We attribute the observed record of deformation to a compressional intraplate stress field, coupled to the progressive evolution of the boundaries of the Indo‐Australian Plate, ensuring that this margin has been subject to ongoing compressional forcing since mid‐Eocene breakup. Our results indicate that compressional deformation at passive margins may be more common than is generally assumed, and that passive margin basins with evidence for protracted post‐breakup deformation histories can provide useful natural laboratories for obtaining improved understanding of the evolution of intraplate stress fields over geological timescales.

Mesozoic to recent evolution of intraplate stress fields under multiple remote stresses: The case of Signy Island (South Orkney Microcontinent, Antarctica)

Abstract Palaeostresses inferred from approximately 3200 brittle mesostructures measured at 43 sites in Signy Island show a stress field characterized by compressional, strike-slip and extensional stress states. There is a dominant NW–SE horizontal compression direction as well as three (NNW–SSE, WNW–ESE and ENE–WSW) secondary σ 1 horizontal stress directions. Orientation of σ 3 shows a main mode trending NW–SE together with secondary north–south and NE–SW extensional stress directions. The NNW–SSE horizontal compression is consistent with the stretching–shearing direction defined from the fold-axis trend. This is owing to a subduction-related tectonic regime during early to middle Jurassic times. In middle Jurassic/early Cretaceous times, the tectonic regime changes to extensional with north–south extensional stress directions. The early processes of subduction of the northern sector of the Weddell Sea oceanic crust below the South Orkney Microcontinent, from the Paleocene until the middle Miocene, is related to the σ 1 direction WNW–ESE to NW–SE. The spreading of Powell Basin took place from the late Eocene to the early Miocene and is the cause of east–west and NE–SW extensional processes in the southern South Orkney Microcontinent. Finally, the NW–SE σ 3 direction is related to the current left-lateral strike-slip movement between the Scotia and Antarctic plates.

Quantifying Neogene plate-boundary controlled uplift and deformation of the southern Australian margin

Abstract Parts of the Australian continent, including the Otway Basin of the southern Australian margin, exhibit unusually high levels of neotectonic deformation for a so-called stable continental region. The onset of deformation in the Otway Basin is marked by a regional Miocene–Pliocene unconformity and inversion and exhumation of the Cretaceous–Cenozoic basin fill by up to c . 1 km. While it is generally agreed that this deformation is controlled by a mildly compressional intraplate stress field generated by the interaction of distant plate-boundary forces, it is less clear whether the present-day record of deformation manifested by seismicity is representative of the longer-term geological record of deformation. We present estimates of strain rates in the eastern Otway Basin since 10 Ma based on seismic moment release, geological observations, exhumation measurements and structural restorations. Our results demonstrate significant temporal variation in bulk crustal strain rates, from a peak of c . 2×10 −16 s −1 in the Miocene–Pliocene to c . 1.09×10 −17 s −1 at the present day, and indicate that the observed exhumation can be accounted for solely by crustal shortening. The Miocene–Pliocene peak in tectonic activity, along with the orthogonal alignment of inverted post-Miocene structures to measured and predicted maximum horizontal stress orientations, validates the notion that plate-boundary forces are capable of generating mild but appreciable deformation and uplift within continental interiors.