Implications For Earthquake Prediction Research Articles

Analysis of Seismic Activity Using Self-Organizing Map: Implications for Earthquake Prediction

Analysis of Seismic Activity Using Self-Organizing Map: Implications for Earthquake Prediction

Spatial and temporal b-value precursors preceding the 2008 Wenchuan, China, earthquake (Mw = 7.9): implications for earthquake prediction

The sudden and unexpected Wenchuan earthquake (Mw = 7.9) occurred on the Longmen Shan Fault without any definite precursors. Therefore, a new computing strategy of b-values was applied in the study area around the epicenter of the Wenchuan mainshock, which is divided into nine circular sub-regions with a radius of 50 km uniformly distributed in space, ignoring geological structures. Then the temporal mapping of b-values is performed at each sub-region. The simulated results show that, at one sub-region where the Wenchuan shock is located, the b-value increased to ∼1.25 in 2002 and was almost unchanged for over five years until 2007. But, the b-value dropped to ∼0.5 in Nov. 2007 and remained the same for about three months. Then, b-value increased again since March 2008, and on May 12, 2008, the Wenchuan mainshock occurred. Indeed, according to previous results, this pattern of b-variations is a typical precursor for major earthquakes, which has not been discovered by many retrospect studies for the Wenchuan earthquake. Therefore, this study, which may capture subtle precursors on b-variations for major earthquakes, is significant for earthquake prediction and seismic hazard assessment.

Numerical simulation of dynamic mechanisms of the 2008 Wenchuan Ms8.0 earthquake: implications for earthquake prediction

The sudden and unexpected Wenchuan earthquake (Ms = 8.0) occurred on the Longmen Shan Fault, causing a large number of casualties and huge property loss. Almost no definite precursors were reported prior to this event by Chinese scientists, who made a first successful prediction of the 1975 Haicheng earthquake (M = 7.3) in China. Does the unsuccessful prediction of the Wenchuan earthquake mean earthquake prediction is inherently impossible? In order to answer this question, the paper simulated inter- and co-seismic deformation, and recurrence of strong earthquakes associated with the Longmen Shan listric thrust fault by means of viscoelastic finite element method. The modeling results show that the computed interseismic strain accumulation in the lower crust beneath the Eastern Tibet is much faster than that in the other regions. In particular, the elastic strain energy density rate accumulates very rapid in and around the Longmen Shan fault in the depth above ~25 km that may explain why the great Wenchuan earthquake occurs in the region of such a slow surface deformation rate. The modeled coseismic displacements around the fault are consistent with surface rupture, aftershock distribution, and GPS measurement. Also, the model displays the slip history on the Longmen Shan fault, implying that the average earthquake recurrence interval on the Longmen Shan fault is very long, 3,300 years, which is in good agreement with the observed by paleoseismological investigations and estimates by other methods. Moreover, the model results indicate that the future earthquake could be evaluated based on numerical computation, rather than on precursors or on statistics. Numerical earthquake prediction (NEP) seems to be a promising avenue to a successful prediction, which will play an important part in natural hazard mitigation. NEP is difficult but possible, which needs well supporting.

Silent earthquakes occurring in a stable-unstable transition zone and implications for earthquake prediction

In the past decade, nine silent earthquakes were documented along the Nankai and the Sagami Troughs in Japan, which form the northwestern margin of the Philippine Sea plate. They occurred in the stable-unstable transition zone at depths of around 30 km on the subduction interface and were segregated from major asperities of the 1923 Kanto, the 1944 Tonankai and the 1946 Nankai earthquakes. Their equivalent magnitudes were less than 7 and overall slips were less than 0.2 m, one-order smaller than those of the major asperities of ordinary great earthquakes. Moment release rates of the silent earthquakes were less than 1014 Nm/s, five-orders smaller than 1019 Nm/s of the great earthquakes. Two methodologies are attempted to obtain order of magnitude estimates of the roughness and friction parameter of source areas of some of the silent earthquakes. One method compares observed waveforms to synthetics with an empirical source time function based on laboratory experiment. The other relates sizes of silent earthquakes to the friction parameter a-b.

The lithosphere of the Earth as a nonlinear system with implications for earthquake prediction

The lithosphere of the Earth can be viewed as a hierarchy of volumes, from tectonic plates to grains of rock. Their relative movement against the forces of friction and cohesion is realized to a large extent through earthquakes. The movement is controlled by a wide variety of independent processes, concentrated in the thin boundary zones between the volumes. A boundary zone has a similar hierarchical structure, consisting of volumes, separated by boundary zones, etc. Altogether, these processes transform the lithosphere into a large nonlinear system, featuring instability and deterministic chaos. From this background some integral grossly averaged empirical regularities emerge, indicating a wide range of similarity, collective behavior, and the possibility of intermediate‐term earthquake prediction.

Synchronized earthquake occurrence in the Hellenic Arc and implications for earthquake prediction in the Dodecanese Islands (Greece)

Seismicity data from 1800 onwards show that large ( M s 7–7.5) shocks in the Western Hellenic Arc are followed on a one-to-one basis by events of M s 6.7–7.5 in the Dodecanese Islands, in the Eastern Hellenic Arc, occurring at a mean distance of 620 ± 102 km from the earlier event after a mean time lag of 2.5 ± 1.7 years. A plate tectonic interpretation is proposed. Should this phenomenon continue to be repeated, a new event of M s ~ 6.7 or larger can be expected to strike in the next few months along one of the two seismic fracture zones in the Dodecanese islands, given that the last large shock in the Western Hellenic Arc occurred 4.7 years ago, which is the maximum estimated time lag.

Interpretation of changes in water level accompanying fault creep and its implications for earthquake prediction : Wesson, R L J Geophys Res, V86, NB10, 10 Oct 1981, P9259–9267

Interpretation of changes in water level accompanying fault creep and its implications for earthquake prediction : Wesson, R L J Geophys Res, V86, NB10, 10 Oct 1981, P9259–9267

Scaling rules in rock fracture and possible implications for earthquake prediction

A major preoccupation in physical sciences has been to interpret macroscopic events from microscopic phenomena. In some cases the change of scale is efficient and fairly easy to perform, but in others it turns out to be difficult and uninteresting. Success or failure is due more to the nature of the events than to the efficiency of the theoretical methods used. Some macroscopic phenomena have their origin in a microscopic organization which can be transferred to larger scales whereas others attain their structure on the macroscopic scale itself. Thus before applying scaling laws techniques1–4 one must ensure that embedded scales are suggested by physical observations. That this seems to be the case for the fracture of rocks is supported by geological, seismological and rock mechanics observations. We have therefore built a very simple model based on scaling laws which yields a criterion for fragility at different scales and views rupture as a critical point. We use this model here to outline a general approach to earthquake prediction.

Interpretation of changes in water level accompanying fault creep and implications for earthquake prediction

Quantitative calculations for the effect of a fault creep event on observations of changes in water level in wells provide an approach to the tectonic interpretation of these phenomena. For the pore pressure field associated with an idealized creep event having an exponential displacement versus time curve, an analytic expression has been obtained in terms of exponential‐integral functions. The pore pressure versus time curves for observation points near the fault are pulselike; a sharp pressure increase (or decrease, depending on the direction of propagation) is followed by more gradual decay to the normal level after the creep event. The time function of the water level change may be obtained by applying the filter—derived by A. G. Johnson and others to determine the influence of atmospheric pressure on water level—to the analytic pore pressure versus time curves. The resulting water level curves show a fairly rapid increase (or decrease) and then a very gradual return to normal. The results of this analytic model do not reproduce the steplike changes in water level observed by Johnson and others. If the procedure used to obtain the water level from the pore pressure is correct, these results suggest that steplike changes in water level are not produced by smoothly propagating creep events but by creep events that propagate discontinously, by changes in the bulk properties of the region around the well, or by some other mechanism. In addition, simplistic calculations show that significant pressure field variations and water level changes near the surface may be expected to accompany a propagating creep event on a buried fault. Water level changes of as much as several meters may be expected at the surface for a creep event having a dislocation amplitude of l m on a semi‐infinite dislocation surface extending downward from a depth of 10 km and propagating horizontally at a rate of 10 km/day. The maximum near‐surface effect should be observed at a horizontal distance from the fault about equal to the depth of the top of the dislocation surface. These results are consistent with the observations made in China of large water level changes preceding large earthquakes, if some sort of aseismic creep event at depth precedes these earthquakes.

Stress Anomaly Accompanying the 1979 Lytle Creek Earthquake: Implications for Earthquake Prediction

An unusual stress transient was recorded 15 kilometers from the epicenter of the Lytle Creek earthquake in southern California. It was observed at the recording site as an increased shear stress parallel to the fault surface and with the proper sense of shear to have triggered the earthquake. The anomaly began 2 to 4 weeks before the earthquake and lasted for 3 months.

Anomalous seismicity prior to rock bursts: Implications for earthquake prediction : Brady, B T Pure Appl Geophys, V115, N1–2, 1977, p357–374

Anomalous seismicity prior to rock bursts: Implications for earthquake prediction : Brady, B T Pure Appl Geophys, V115, N1–2, 1977, p357–374

The economic issues

Expectations are a major factor in economic behaviour. If we expect prices to rise, we buy now rather than later, increasing the demand for goods and ensuring that their prices will indeed increase. If we expect share prices to fall, and act on that premise, share prices will fall. Expectations of an economic recovery will stimulate investment and speed the recovery. They are, to a degree, self-fulfilling. This has obvious implications for earthquake prediction. If the prediction is believed, it will have economic consequences. In this paper I suggest that the economic consequences of such a prediction may be as important as the impact of the earthquake itself.

Anomalous seismicity prior to rock bursts: Implications for earthquake prediction

Anomalous seismicity prior to rock bursts: Implications for earthquake prediction

Seismology and the new global tectonics: Implications for earthquake prediction

A comprehensive study of the observations of seismology provides widely based, strong support for the new global tectonics that is founded on the hypotheses of continental drift, sea‐floor spreading, transform faults, and underthrusting of the lithosphere at island arcs. Although further developments will be required to explain certain parts of the seismological data, at present within the entire field of seismology there appear to be no serious obstacles to the new tectonics.Seismic phenomena are explained, in general, as the result of interactions and other processes at or near the edges of a few large mobile plates of lithosphere that spread apart at the ocean ridges where new surficial materials arise, slide past one another along the large strike‐slip faults, and converge at the island arcs and arc‐like structures where surficial materials descend.