Aftershock Sequences Of Earthquakes Research Articles

Исследование афтершоковой последовательности Суусамырского землетрясения

Исследование афтершоковой последовательности Суусамырского землетрясения

A Quantitative Estimate of the Effects of Sea Tides on Aftershock Activity: Kamchatka

The issue of whether tidal forces really affect seismicity has been raised many times in the literature. Nevertheless, even though there seems to be a kind of consensus that such effects do exist, no quantitative estimates are available to relate tide parameters to changes in the level of seismic activity. Such estimation for aftershocks of large earthquakes near Kamchatka is the goal of the present study. We consider the influence on seismicity due to ocean tides only, because their effects are stronger than those of solid earth tides. Accordingly, we only consider earthquakes that occurred in the ocean. One important feature that distinguishes the present study from most other such research consists in the fact that we study the height of ocean tides and its derivative rather than tidal phases as the decisive factors. We considered 16 aftershock sequences of earthquakes near Kamchatka with magnitudes of 6 or greater. We also examined shallow background earthquakes along the coast of Kamchatka. Our basic model of aftershock rate was the Omori–Utsu law. The background seismicity distribution was assumed to be uniform over time. In both of these cases we used the actual distributions in space. The heights of sea tides were estimated using the FES 2004 model (Lyard et al., 2006). The variation in activity from what the basic model assumes in relation to tidal wave height and its time derivative was estimated by the method of differential probability gain. The main practical result of this study consists in estimates of averaged differential probability gain functions for aftershock rate with respect to both of the considered factors. These estimates can be used for earthquake hazard assessment from aftershocks with ocean tides incorporated. The results of our analysis show a persistent tendency of aftershock rate increasing during periods when the ocean tide decreased at a high rate. For the background events, we found a typical tendency of events rate increasing when the ocean tide decreased with high tidal amplitudes. The difference in the main factors that affect aftershocks and background seismicity suggest the inference that the effects of tides on aftershocks are more likely to be direct dynamic initiation of events during high strain rates, while the effects on the background events were static in character.

Long-Delayed Aftershocks in New Zealand and the 2016 M7.8 Kaikoura Earthquake

We study aftershock sequences of six major earthquakes in New Zealand, including the 2016 M7.8 Kaikaoura and 2016 M7.1 North Island earthquakes. For Kaikaoura earthquake, we assess the expected number of long-delayed large aftershocks of M5+ and M5.5+ in two periods, 0.5 and 3 years after the main shocks, using 75 days of available data. We compare results with obtained for other sequences using same 75-days period. We estimate the errors by considering a set of magnitude thresholds and corresponding periods of data completeness and consistency. To avoid overestimation of the expected rates of large aftershocks, we presume a break of slope of the magnitude–frequency relation in the aftershock sequences, and compare two models, with and without the break of slope. Comparing estimations to the actual number of long-delayed large aftershocks, we observe, in general, a significant underestimation of their expected number. We can suppose that the long-delayed aftershocks may reflect larger-scale processes, including interaction of faults, that complement an isolated relaxation process. In the spirit of this hypothesis, we search for symptoms of the capacity of the aftershock zone to generate large events months after the major earthquake. We adapt an algorithm EAST, studying statistics of early aftershocks, to the case of secondary aftershocks within aftershock sequences of major earthquakes. In retrospective application to the considered cases, the algorithm demonstrates an ability to detect in advance long-delayed aftershocks both in time and space domains. Application of the EAST algorithm to the 2016 M7.8 Kaikoura earthquake zone indicates that the most likely area for a delayed aftershock of M5.5+ or M6+ is at the northern end of the zone in Cook Strait.

Automatic analysis of the Gorkha earthquake aftershock sequence: evidences of structurally segmented seismicity

We present the first 3 months of aftershock activity following the 2015 April 25 Gorkha earthquake M w 7.8 recorded on the Nepalese Seismic network. We deployed an automatic procedure composed of three main stages: (1) coarse determination of the P and S onsets; (2) phase association to declare events and (3) iterative addition and refinement of onsets using the Kurtosis characteristic function. In total 9188 events could be located in the Kathmandu region with the majority having small location errors (<4.5, 9 and 10 km in the X-, Y-and Z-directions, respectively). Additionally, we propose a new attenuation law to estimate local magnitudes in the region. This new seismic catalogue reveals a detailed insight into the Gorkha aftershock sequence and its relation to the main shock rupture models and tectonic structures in the region. Most aftershocks fall within the Main Himalayan Thrust (MHT) shear zone or in its hangingwall. Significant temporal and lateral variations of aftershocks location are observed among them: (1) three distinct stages, highlighting subsequent jump-offs at the easternmost termination, (2) the existence of a seismic gap north of Kathmandu which matches with a low slip zone in the rupture area of the main shock, (3) the confinement of seismic activity in the trace of the May 12 M w 7.3 earthquake within the MHT and its hangingwall through a 30 × 30 km 2 region and (4) a shallow westward-dipping structure east of the Kathmandu klippe. These new observations with the inferred tectonic structures at depth suggest a tectonic control of part of the aftershock activity by the lateral breaks along the MHT and by the geometry of the duplex above the thrust.

EARTHQUAKE RELOCATION IN GREECE USING A UNIFIED AND HOMOGENIZED SEISMOLOGICAL CATALOGUE

In this study phase data from the Cornet seismological network installed by the Geophysics-Geothermics Department (University of Athens) and the permanent networks of the Geodynamic Institute of the National Observatory of Athens and of the Geophysics Department of Thessaloniki (Aristotle University), for the decade 1996-2006, were merged. The data were jointly used to relocate the earthquakes that occurred in the broader area of Greece. Initially, single-event algorithms were applied by minimizing spatiotemporal residuals. Following, the hypocenters were relocated using a doubledifference algorithm where rms, as well as the horizontal and vertical location errors (erh, erz) were minimized and a consequence of that better locations were achieved. After that process the spatial distribution of the epicenters outlined major local tectonic features in Greece. Moreover, the same methodology was applied to the aftershock sequences of large earthquakes and the results were successfully compared with those obtained by available local networks that were deployed.

Statistical analysis of aftershock sequences related with two major Nepal earthquakes: April 25, 2015, MW 7.8, and May 12, 2015, MW 7.2

Present study describes the statistical properties of aftershock sequences related with two major Nepal earthquakes (April 25, 2015, MW 7.8, and May 12, 2015, MW 7.2) and their correlations with the tectonics of Nepal Himalaya. The established empirical scaling laws such as the Gutenberg–Richter (GR) relation, the modified Omori law, and the fractal dimension for both the aftershock sequences of Nepal earthquakes have been investigated to assess the spatio-temporal characteristics of these sequences. For this purpose, the homogenized earthquake catalog in moment magnitude, MW is compiled from International Seismological Center (ISC) and Global Centroid Moment Tensor (GCMT) databases during the period from April 25 to October 31, 2015. The magnitude of completeness, MC, a and b-values of Gutenberg–Richter relationship for the first aftershock sequence are found to be 3.0, 4.74, 0.75 (±0.03) respectively whereas the MC, a and b-values of the same relationship for the second aftershock sequence are calculated to be 3.3, 5.46, 0.90 (±0.04) respectively. The observed low b-values for both the sequences, as compared to the global mean of 1.0 indicate the presence of high differential stress accumulations within the fractured rock mass of Nepal Himalaya. The calculated p-values of 1.01 ± 0.05 and 0.95 ± 0.04 respectively for both the aftershock sequences also imply that the aftershock sequence of first main-shock exhibits relatively faster temporal decay pattern than the aftershock sequence of second main-shock. The fractal dimensions, DC values of 1.84 ± 0.05 and 1.91 ± 0.05 respectively for both the aftershock sequences of Nepal earthquakes also reveal the clustering pattern of earthquakes and signifies that the aftershocks are scattered all around the two dimensional space of fractured fault systems of the Nepal region. The low b-value and low DC observed in the temporal variations of b-value and DC before the investigated earthquake (MW 7.2) suggest the presence of high-stress concentrations in the thrusting regimes of the Nepal region before the failure of faults. Moreover, the decrease of b-value with the corresponding decrease of DC observed in their temporal variations can primarily act as an indicator for possible prediction of major earthquakes in the study region.

Improvement of robustness and stability in estimating Rayleigh–Schuster’s hodograph parameters using different procedures of vector normalization

This paper deals with Rayleigh–Schuster’s hodographs, intended for the detailed investigation of changes in the phase of quasiperiodic signals in time series. The hodographs are also known as the phasor-walkout method. A procedure of conditional vector normalization is proposed: it takes into account the vector amplitude for each period under consideration. The procedure considerably improves the robustness and stability of the hodograph approach to changes in the character of the processed data distributions and to various defects in the data. For example, when analyzing the earthquake catalog, the procedure strongly diminishes the influence of the event clustering caused, in particular, by swarms of earthquakes with comparable magnitude and the aftershock sequences of strong earthquakes. At the first stage, we calculate the vector sums (resulting vectors) for each period under investigation throughout the time series duration. For example, investigating diurnal periodicity of earthquakes, we first calculate the resulting vectors for each day of the observation. The further analysis of resulting vectors for each period throughout the time series duration can be performed with different procedures. We compare three procedures for normalization of the obtained resulting vectors, which are as follows: (1) th traditional one, preserving the real signal amplitude; (2) that with reduction of the obtained resulting vectors to the unit vector (phasor); and (3) that with conditional vector normalization, taking into account the amplitude of resulting vectors for each period throughout the time series duration. The third procedure diminishes the possible instability in some special distributions of the investigated data when the resulting vector for a period is close to zero. The procedures are compared using model signals and samples from real earthquake catalogs. All the procedures used give close results when processing random time series.

Evidence of non extensivity in the evolution of seismicity along the San Andreas Fault, California, USA: An approach based on Tsallis statistical physics

We examine the nature of the seismogenetic system along the San Andreas Fault (SAF), California, USA, by searching for evidence of complexity and non-extensivity in the earthquake record. We use accurate, complete and homogeneous earthquake catalogues in which aftershocks are included (raw catalogues), or have been removed by a stochastic declustering procedure (declustered catalogues). On the basis of Non-Extensive Statistical Physics (NESP), which generalizes the Boltzmann–Gibbs formalism to non-equilibrating (complex) systems, we investigate whether earthquakes are generated by an extensive self-excited Poisson process or by a non-extensive complex process. We examine bivariate cumulative frequency distributions of earthquake magnitudes and interevent times and determine the size and time dependence of the respective magnitude and temporal entropic indices, which indicate the level on non-equilibrium (correlation). It is shown that the magnitude entropic index is very stable and corresponds to proxy b-values that are remarkably consistent with the b-values computed by conventional means. The temporal entropic index computed from the raw catalogues indicate moderately to highly correlated states during the aftershock sequences of large earthquakes, progressing to quasi-uncorrelated states as these die out and before the next large event. Conversely, the analysis of the declustered catalogues shows that background seismicity exhibits moderate to high correlation that varies significantly albeit smoothly with time. This indicates a persistent sub-extensive seismogenetic system. The degree of correlation is generally higher in the southern SAF segment, which is consistent with the observation of shorter return periods for large earthquakes. A plausible explanation is that because aftershock sequences are localized in space and time, their efficient removal unveils long-range background interactions which are obscured by their presence! Our results indicate complexity in the expression of background seismicity along the San Andreas Fault, with criticality being a very likely mechanism as a consequence of the persistent non-equilibrium inferred from the temporal entropic index. However, definite conclusions cannot be drawn until the earthquake record is exhaustively studied in all its forms.

Infrasonic Signals Associated with the Aftershocks of LuShan Earthquake of April 20th, 2013

On April 20th, 2013, a strong earthquake (Ms 7.0, depth of 13 km) occurred in LuShan County, Southwestern Sichuan province, China, followed by a series of aftershocks (Ms = 3.0∼5.4). Infrasonic waves associated with the earthquake were detected and recorded by a digital infrasound recording system in our lab located in Chengdu city. Fourier analysis was used to determine the amplitude and frequency characteristics of each infrasonic recording. A certain frequency distribution range was clearly identified in the spectrograms of all analyzed shocks. Furthermore, a logarithm regression relation is also found between aftershock magnitude and peak value of corresponding infrasound events in amplitude spectra based on analysis results of more than 30 observed events. This study presents a data set and an empirical relationship. This relationship requires additional testing with observations from other earthquake aftershock sequences. These results improve our understanding of local infrasound produced by the coupling of earth surface motion to the atmosphere.

Resolution of non-double-couple components in the seismic moment tensor using regional networks—I: a synthetic case study

We perform a detailed synthetic study on the resolution of non-double-couple (non-DC) components in the seismic moment tensors from short-period data observed at regional networks designed typically for monitoring aftershock sequences of large earthquakes. In addition, we test two different inversion approaches—a linear full moment tensor inversion and a non-linear moment tensor inversion constrained to a shear-tensile source model. The inversions are applied to synthetic first-motion P- and S-wave amplitudes, which mimic seismic observations of aftershocks of the 1999 Mw = 7.4 Izmit earthquake in northwestern Turkey adopting a shear-tensile source model. To analyse the resolution capability for the obtained non-DC components inverted, we contaminate synthetic amplitudes with random noise and incorporate realistic uncertainties in the velocity model as well as in the hypocentre locations. We find that the constrained moment tensor inversion yields significantly smaller errors in the non-DC components than the full moment tensor inversion. In particular, the errors in the compensated linear vector dipole (CLVD) component are reduced if the constrained inversion is applied. Furthermore, we show that including the S-wave amplitudes in addition to P-wave amplitudes into the inversion helps to obtain reliable non-DC components. For the studied station configurations, the resolution remains limited due to the lack of stations with epicentral distances less than 15 km. Assuming realistic noise in waveform data and uncertainties in the velocity model, the errors in the non-DC components are as high as ±15 per cent for the isotropic and CLVD components, respectively, thus being non-negligible in most applications. However, the orientation of P- and T-axes is well determined even when errors in the modelling procedure are high.

Communicating likelihoods and probabilities in forecasts of volcanic eruptions

The issuing of forecasts and warnings of natural hazard events, such as volcanic eruptions, earthquake aftershock sequences and extreme weather often involves the use of probabilistic terms, particularly when communicated by scientific advisory groups to key decision-makers, who can differ greatly in relative expertise and function in the decision making process. Recipients may also differ in their perception of relative importance of political and economic influences on interpretation. Consequently, the interpretation of these probabilistic terms can vary greatly due to the framing of the statements, and whether verbal or numerical terms are used. We present a review from the psychology literature on how the framing of information influences communication of these probability terms. It is also unclear as to how people rate their perception of an event's likelihood throughout a time frame when a forecast time window is stated. Previous research has identified that, when presented with a 10-year time window forecast, participants viewed the likelihood of an event occurring ‘today’ as being of less than that in year 10. Here we show that this skew in perception also occurs for short-term time windows (under one week) that are of most relevance for emergency warnings. In addition, unlike the long-time window statements, the use of the phrasing “within the next…” instead of “in the next…” does not mitigate this skew, nor do we observe significant differences between the perceived likelihoods of scientists and non-scientists. This finding suggests that effects occurring due to the shorter time window may be ‘masking’ any differences in perception due to wording or career background observed for long-time window forecasts. These results have implications for scientific advice, warning forecasts, emergency management decision-making, and public information as any skew in perceived event likelihood towards the end of a forecast time window may result in an underestimate of the likelihood of an event occurring ‘today’ leading to potentially inappropriate action choices. We thus present some initial guidelines for communicating such eruption forecasts.

Aftershock Statistics of Major Subduction Earthquakes

Abstract Large megathrust subduction earthquakes generate prolific aftershock sequences which last over an extended period of time and affect wide spatial areas. Among those aftershocks, the largest ones can cause additional damage and pose significant risks to population and infrastructure. Therefore, modeling aftershock sequences of large subduction earthquakes is of considerable importance for seismic‐hazard assessment and earthquake risk mitigation. It can also play a prominent role in the ground‐shaking modeling of major mainshock–aftershock sequences. In this work, we analyze statistical properties of aftershock sequences of large subduction earthquakes worldwide which occurred from 1973 to present, including recent catastrophic events in Sumatra, Chile, and Japan. We use information provided in the National Earthquake Information Center (NEIC) catalog to extract 70 aftershock sequences generated by mainshocks of M 7.0 and above. We construct their temporal decay rates and magnitude–frequency statistics. To model their temporal behavior, we estimate the parameters of the modified Omori law. In the magnitude domain, we model the frequency–magnitude statistics using the Gutenberg–Richter scaling relationship. We also analyze statistically the difference between the magnitude of the mainshock and the corresponding largest aftershock in the sequence and discuss this in terms of Bath’s law. One of the main goals of this work is to investigate the variation in parameter values of the above empirical laws with respect to the magnitude of the mainshock. Our main finding indicates that most parameters do not depend on the magnitude of the mainshock. However, they show some variation in values across different subduction settings. Online Material: The location and spatial information for elliptical regions of aftershock zones.

Seismic swarms, fluid flow and hydraulic conductivity in the forearc offshore North Costa Rica and Nicaragua

At the continental margin of north Costa Rica and Nicaragua, the strongly hydrated Cocos Plate subducts beneath the Caribbean Plate. From the downgoing Cocos plate fluids are released through extensional fractures in the overriding plate. At the seafloor, they form fluid seeps, mounds and other types of fluid expulsion. Using an offshore temporary seismic network, we investigated seismicity possibly related to these processes and observed several swarms of earthquakes located on the continental slope trenchward of the seismogenic zone of S Nicaragua. The seismicity occurred within the downgoing plate, near the plate interface and in the overriding plate. We interpret these swarm events as an expression of pore pressure propagation under critical stress conditions driven by fluid release from the downgoing plate. In order to estimate hydraulic diffusivity and permeability values, we applied a theory developed for injection test interpretation to the spatio-temporal development of the swarms. The resulting diffusivity and permeability values are in the ranges of 28–305 m²/s and 3.2 × 10−14 m²–35.1 × 10−14 m², respectively, applying to the continental and oceanic crust near the plate interface. These values are somewhat larger than observed in drill logs on the margin wedge off north Costa Rica, but of comparable magnitude to values estimated for the Antofagasta 1995 earthquake aftershock sequence.

The 1991 Racha earthquake, Caucasus: Multiple source model with compensative type of motion

The source of the 1991 Racha earthquake in the Greater Caucasus generally corresponds to thrusting, which is characteristic of the predominant regional compression stress field. A more adequate view of the rupture process is provided by a complex source model composed of three subsources. This model is reconstructed by the body-wave inversion and consistent with the spatial distribution of the aftershocks. In terms of the suggested model, at the last stage of the rupture process, the opposite slip type (normal faulting) is observed in the source, which seems to be objective. It compensates the rapid (probably short) local redistribution of stresses caused by the thrusts in the first two subsources. The surface deformations observed in the epicentral zones of strong earthquakes are probably the analogs of such a compensative mechanism. For example, in the rear parts of the thrusts associated with the surface ruptures, normal faults trending parallel to the strike of the thrust line occur. Another analog of the compensative motion is probably the peculiarities of the aftershock sources. It has long since been noted (Kuznetsova et al., 1976) that some fault plane solutions in the aftershock sequences of strong earthquakes are close to the main shock solution, while others are different. The explanation of this phenomenon is suggested in (Kuznetsova et al., 1976; Kostrov and Das, 1988). In (Kuznetsova et al., 1976), these events are referred to as the aftershocks due to the fracture growth and aftershocks of relaxation, respectively.

The 2010 Mw 6.5 Rigan, Iran, Earthquake Aftershock Sequence

Abstract The 20 December 2010 M w 6.5 Rigan earthquake that occurred in southeastern Iran was followed by an extensive aftershock sequence. A six‐station portable seismographic network was deployed by the Institute of Geophysics at the University of Tehran around Rigan in Kerman province. To understand the aftershock activity, we have used the data recorded by this temporary seismic network. Distribution of the aftershocks shows that the earthquake sequence occurred along a right‐lateral strike‐slip fault with a northeast–southwest trend. The general pattern of the aftershocks distribution delineates a source fault with a length of approximately 20 km along strike and ∼5 km across the surface. This source fault dips steeply southeastward and strikes along a nearly northeast–southwest line. The depth range of the aftershocks is 1–12 km. The aftershock activity has its highest concentration in the northern part of the active fault, and tapers off toward the southwestern part of the active fault segment, indicating mainly a unilateral rupture. On 27 January 2011, another moderate‐sized earthquake ( M w 6.2) occurred a few kilometers away from the southwestern end of the active zone, which probably represents a slow diffusion of stress away from the main rupture. Online Material: Aftershock catalog.

Comparing the Hawkes and Trigger Process Models for Aftershock Sequences Following the 2005 Kashmir Earthquake

In an earlier study (Van Lieshout and Stein in Math Gesoci 44(3):309–326, 2012) we postulated the existence of two major earthquakes in the 2005 Kashmir disaster instead of a single one, based upon the pattern of aftershocks. In this study, we explore this hypothesis further by fitting several spatial point pattern models. In particular, we discuss the Hawkes and the trigger process models for earthquake aftershock sequences following the Kashmir catastrophe in 2005. The minimum contrast method is used for estimation of the parameters. The study shows that the trigger model fits better than the Hawkes model. The most likely number of main shocks is rounded to 2 generating the almost 200 aftershocks, whereas the Hawkes model would estimate a parent process of approximately 18 parents with on average about 10 descendants. We conclude that the spatial pattern of aftershocks can best be understood as a mixture of two bivariate normal distributions centered around two major shocks and estimate the parameters.

Identification of earthquake aftershock and swarm sequences in the Baikal rift zone

The catalog of earthquakes (КR³6.6) which occurred in the Baikal rift zone (BRZ) was declastered, and the results are presented in the article. Aftershocks of seismic events (КR³12.5) were determined by the software developed by V.B. Smirnov (Lomonosov Moscow State University) with application of the algorithm co-authored by G.M. Molchan and O.E. Dmitrieva. To ensure proper control of the software application, aftershocks were also selected manually. The results of declustering show that aftershocks of the earthquakes (КR³12.5) account for about 25 per cent of all seismic events in the regional catalog. Aftershocks accompanied 90 per cent of all the earthquakes considered as main shocks. Besides, earthquake swarms, including events with КR³11, were identified. The results of this study show that, in the BRZ, the swarms and strong events with aftershocks are not spatially separated, and this conclusion differs from the views of the previous studies that reviewed data from a shorter observation period. Moreover, it is noted that the swarms may consist of several main shocks accompanied by aftershocks. The data accumulated over the last fifty years of instrumental observations support the conclusion made earlier that the swarms in BRZ occur mainly in the north-eastward direction from Lake Baikal and also confirm the trend of a small number of aftershocks accompanying earthquakes in the south-western part of the Baikal rift zone.

A detailed b-value and fractal dimension study of the March 1999 Chamoli earthquake (M s 6.6) aftershock sequence in western Himalaya

The aftershock sequence of the March 1999 Chamoli earthquake (M s 6.6) in the western Himalaya is analysed to examine the seismic characteristics of the active fault. About 350 aftershocks recorded by about 40 seismic stations are used to map the b-value and fractal correlation dimension (D c) in the earthquake source area. The maximum likelihood method is used to estimate the b-value, and the correlation integral method for the fractal correlation dimension. A comparatively higher b-value (0.7) is mapped to the north at the Main Central Thrust (MCT) zone with respect to a lower b-value (0.5) to the south at the Alakananda fault (ANF) zone. The cross section of the b-value imaged the seismically active ANF at depth. The fractal dimension map, on the other hand, identified the ANF with D c ∼0.8–0.9, that implies a near linear seismogenic structure at the ANF.

Statistical analysis of the 2010 M W 7.1 Darfield Earthquake aftershock sequence

Statistical properties of the aftershock sequence of the M W 7.1 Darfield (Canterbury, New Zealand) earthquake are studied. The sequence exhibits rich scaling behaviour in magnitude and aftershock decay rates. In particular, we observe a marked variability in the frequency-magnitude statistics in space, between early and late times after the mainshock and over different magnitude ranges. The mainshock triggered two large earthquakes (22 February 2011 M W 6.2 Christchurch earthquake and 13 June 2011 M W 6.0 earthquake) that occurred later in the sequence and generated their own aftershock sequences. The frequency-magnitude statistics of the sequences are modelled using the Gutenberg–Richter scaling relation. We also study the difference between the magnitudes of the largest recorded aftershocks and the mainshock. This is analysed and discussed using the modified Båth law. In this context we consider the M W 6.2 Christchurch and 13 June 2011 M W 6.0 earthquakes as the largest aftershocks of the Darfield mainshock. It is also observed that the aftershock decay rates can be approximated by the modified Omori law. The obtained results indicate that the aftershock sequence exhibits self-similarity in both magnitude and time.

A non-extensive statistical physics view to the spatiotemporal properties of the June 1995, Aigion earthquake (M6.2) aftershock sequence (West Corinth rift, Greece)

In the present study, the spatiotemporal properties of the Aigion earthquake (15 June 1995) aftershock sequence are being studied using the concept of non-extensive statistical physics (NESP). The cumulative distribution functions of the inter-event times and the inter-event distances are being estimated for the data set which is assumed to be complete and the analysis yielded the thermodynamic q parameter to be qT = 1.58 and qr = 0.53 for the two distributions, respectively. The results fit rather well to the inter-event distances and times distributions, implying the complexity of the spatiotemporal properties of seismicity and the usefulness of NESP in investigating such phenomena. The temporal structure is also being discussed using the complementary to NESP approach of superstatistics, which is based on a superposition of ordinary local equilibrium statistical mechanics. The result indicates that very low degrees of freedom describe the temporal evolution of the Aigion earthquake aftershock seismicity.