A Case For Historic Joint Rupture Of The San Andreas And San Jacinto Faults

The San Andreas fault is considered to be the primary plate boundary fault in southern California and the most likely fault to produce a major earthquake. I use dynamic rupture modeling to show that the San Jacinto fault is capable of rupturing along with the San Andreas in a single earthquake, and interpret these results along with existing paleoseismic data and historic damage reports to suggest that this has likely occurred in the historic past. In particular, I find that paleoseismic data and historic observations for the ~M7.5 earthquake of 8 December 1812 are best explained by a rupture that begins on the San Jacinto fault and propagates onto the San Andreas fault. This precedent carries the implications that similar joint ruptures are possible in the future and that the San Jacinto fault plays a more significant role in seismic hazard in southern California than previously considered. My work also shows how physics-based modeling can be used for interpreting paleoseismic data sets and understanding prehistoric fault behavior.Science Advances 2(3), e1500621. (2016)2375-254

Dormancy-Breaking Requirements and Germination for Seeds of Ostrya carpinifolia Scop.

The present research aims at investigating the combined effects of warm stratification (WS)+cold stratification (CS), and gibberellic acid (GA3)+cold stratification (CS) on breaking dormancy and germination in seeds of Ostrya carpinifolia. The seeds were subjected to WS (20-25 °C) for 0, 1 and 2 months and were subsequently cold stratified at 3-5 °C for 0, 1, 2, 3 and 4 months (1st experiment). A further amount of seeds was treated with 500, 1000 or 2000 ppm GA3 for 30 hours and then cold stratified at 3-5 °C for 0, 1, 2, 3 and 4 months (2nd experiment). No germination was observed in the seeds subjected to only WS (1 and 2 months) or CS for 1 month indicating that the seeds of O. carpinifolia are dormant. A 4-month stratification (1 month WS+3 month CS or 4 months CS) fully released dormancy and led to a high germination percentage (94.17 and 98.34% respectively) in a short time (7.12 and 7.00 days respectively). Warm stratification treatment prior to CS, was not required in order to break the seed dormancy of O. carpinifolia and also did not reduce the length of the (total) stratification period required for breaking seed dormancy. Gibberellic acid (GA3) application entirely replaced the CS period required for breaking seed dormancy. The germination of the seeds treated only with 2000 ppm GA3 (0 months of CS) was (94.17%) as high as the germination of the seeds subjected to 4 months of CS (98.34%). It is obvious that the seedcoat of O. carpinifolia seeds was permeable to GA3 and did not mechanically restrict embryo growth, thus, the seeds did not exhibit physical dormancy. Based on dormancy breaking requirements, the O. carpinifolia seeds displayed intermediate physiological dormancy

Dynamic Rupture and Ground Motion Modeling on Realistically Complex Strike-Slip Faults

Faults are complex structures: they are geometrically complex, and have variable stress conditions and frictional behaviors along their length. In addition, faults exist in heterogeneous settings, in terms of surrounding geology, and in terms of regional and local stresses. These individual types of heterogeneity all contribute to complex dynamic rupture behaviors and ground motion distributions, as inferred from observational data and supported by previous modeling studies. In this study, we investigate the effects of individual types of complexity, and we combine different types of heterogeneity in order to enhance the realism of models of real-world faults.We use the finite element method to conduct dynamic rupture models of earthquakes on faults with complex geometry, initial stresses, frictional parameters, and surrounding geology, and with combinations of these factors, in order to investigate the effects of this complexity on fault interactions, rupture extent, and ground motion. In particular, we investigate the effect of critical weakening distance on the ability of rupture to propagate through a discontinuity in the fault trace, the effect of a small fault between the larger strands of a stepover on the ability of rupture to jump the stepover, and how zones of aseismic creep affect rupture through locked portions of the same fault. We also construct realistically complex models of the northern San Jacinto Fault, California, incorporating realistic geometry, velocity structure, and combined regional and stochastic stress fields.We find that the distribution of complexity of any type on the fault, which leads to heterogeneous fault strength, has the primary controlling effect on rupture behavior. The relative strength or weakness of the fault, rather than the actual value, is most important. We also find that the balance of the energy budget is crucial; if too much energy is redirected into fracture, rupture stops. Lastly, we find that each type of complexity affects rupture in its own way, but it is difficult to separate out the effects of individual factors in a model that incorporates many types of heterogeneity. We therefore emphasize the importance of including as many types of realistic complexity as feasible when modeling real faults

The effect of along-strike variation in dip on rupture propagation on strike-slip faults

AbstractStrike-slip faults can be nonplanar in both their strike and dip dimensions. While a large body of work has investigated the effects of changes in strike on earthquake rupture and arrest, no previous studies have investigated the role of along-strike variations in dip on strike-slip ruptures. Here, I use the three-dimensional finite-element method to conduct dynamic simulations of ruptures on strike-slip faults with linear surface traces and changes in dip along strike. I experiment with the amount of dip change as well as the abruptness of that change under a variety of initial stress conditions. In all of my initial stress cases, I find that a change in dip along strike can cause rupture to stop, and that larger dip changes over shorter distances are more likely to do so. This is largely due to the change in strike at depth that inherently comes from changing the dip; the majority of these behaviors are a result of the rupture front being forced to change direction mid-rupture. While some dip-slip movement does occur on the nonvertical parts of the model fault, it does not have a significant effect on rupture extent. However, linear-surface-trace, nonvertical-dip faults do produce different surface slip, stress, and ground motion patterns compared to corresponding nonlinear-strike, vertical-dip faults. Together, my results show that changes in dip along strike-slip faults do considerably impact the rupture process, suggesting that this type of geometrical complexity should be considered in rupture forecasts and hazard assessments.</jats:p

Dynamic Rupture and Ground Motion Modeling on Realistically Complex Strike-Slip Faults

Faults are complex structures: they are geometrically complex, and have variable stress conditions and frictional behaviors along their length. In addition, faults exist in heterogeneous settings, in terms of surrounding geology, and in terms of regional and local stresses. These individual types of heterogeneity all contribute to complex dynamic rupture behaviors and ground motion distributions, as inferred from observational data and supported by previous modeling studies. In this study, we investigate the effects of individual types of complexity, and we combine different types of heterogeneity in order to enhance the realism of models of real-world faults.We use the finite element method to conduct dynamic rupture models of earthquakes on faults with complex geometry, initial stresses, frictional parameters, and surrounding geology, and with combinations of these factors, in order to investigate the effects of this complexity on fault interactions, rupture extent, and ground motion. In particular, we investigate the effect of critical weakening distance on the ability of rupture to propagate through a discontinuity in the fault trace, the effect of a small fault between the larger strands of a stepover on the ability of rupture to jump the stepover, and how zones of aseismic creep affect rupture through locked portions of the same fault. We also construct realistically complex models of the northern San Jacinto Fault, California, incorporating realistic geometry, velocity structure, and combined regional and stochastic stress fields.We find that the distribution of complexity of any type on the fault, which leads to heterogeneous fault strength, has the primary controlling effect on rupture behavior. The relative strength or weakness of the fault, rather than the actual value, is most important. We also find that the balance of the energy budget is crucial; if too much energy is redirected into fracture, rupture stops. Lastly, we find that each type of complexity affects rupture in its own way, but it is difficult to separate out the effects of individual factors in a model that incorporates many types of heterogeneity. We therefore emphasize the importance of including as many types of realistic complexity as feasible when modeling real faults

Πειραματικό μοντέλο ισχαιμικής βλάβης νωτιαίου μυελού και καθυστερημένης νευρολογικής βλάβης

Εισαγωγή: Οι αγωνιστές των διαύλων καλίου τριφωσφορικής αδενοσίνης (KATP) εμπλέκονται στην ευόδωση της ανοχής της ισχαιμίας σε διάφορους ιστούς. Ο σκοπός αυτής της μελέτης είναι η αξιολόγηση των επιδράσεων της απρικαλίμης, ενός εκλεκτικού αγωνιστή των διαύλων KATP, όσον αφορά στην ισχαιμική βλάβη του νωτιαίου μυελού. Υλικό και μέθοδοι: 44 κόνικλοι κατανεμήθηκαν τυχαία σε τρεις ομάδες: ομάδα 1 (n=18, sham χειρουργείο), ομάδα 2 (n=18, 30 min νορμοθερμικού αποκλεισμού της αορτής) και ομάδα 3 (n=18, χορήγηση απρικαλίμης 100 mg/kg 15 min πριν από 30 min νορμοθερμικού αποκλεισμού της αορτής). Η νευρολογική εκτίμηση έγινε με βάση την τροποποιημένη κλιμακα Tarlov. Έξι ζώα από κάθε ομάδα θυσιάστηκαν στις 24, 48 και 168 ώρες μετεγχειρητικά. Η οσφυϊκή μοίρα του νωτιαίου μυελού αφαιρέθηκε και εξετάστηκε ιστολογικά. Μετρήθηκαν οι κινητικοί νευρώνες και οι ιστολογικές βλάβες βαθμολογήθηκαν (0-3, 3: φυσιολογικό). Αποτελέσματα: Η ομάδα 3 (ομάδα απρικαλίμης) παρουσιάζει καλύτερη βαθμολογία στην κλίμακα Tarlov σε σύγκριση με την ομάδα 2 σε όλες τις χρονικές στιγμές (P &lt; 0.025). Οι ιστολογικές μεταβολές ήταν ανάλογες με τις βαθμολογίες της κλιμακας Tarlov και η ομάδα 3 είχε καλύτερο λειτουργικό αποτέλεσμα σε σύγκριση με την ομάδα 2 στις 168 ώρες (αριθμός νευρώνων: 21.2 4.9 vs. 8.0 ± 2.7, P &lt; 0.001 και ιστολογική βαθμολογία: 1.67 ± 1.03 vs. 0.50 ± 0.55, P=0.03). Παρόλο που η απρικαλίμη παρουσίασε θετικές επιδράσεις όσον αφορά στα κλινικά και ιστολογικά αποτελέσματα σε σύγκριση με την νορμοθερμική ισχαιμία του νωτιαίου μυελού η ομάδα 3 παρουσίασε ωστόσο χειρότερη βαθμολογία στην κλίμακα Tarlov και μειωμένο αριθμό νευρώνων και χαμηλότερη ιστολογική βαθμολογία σε σύγκριση με την ομάδα 1 (sham χειρουργείο) στις 168 ώρες (P=0.003, P=0.001 and P=0.019 αντιστοίχως). Συμπεράσματα: Η απρικαλίμη μειώνει την έκταση της ισχαιμικής βλάβης του νωτιαίου μυελού σε πειραματικό μοντέλο ισχαιμίας νωτιαίου μυελού σε κονίκλους.Introduction: Potassium adenosine triphosphate (KATP) channel openers have been involved in the enhancement of ischemic tolerance in various tissues. The purpose of the present study is to evaluate the effects of aprikalim, a specific KATP channel opener, on spinal cord ischemic injury. Materials and methods: Fifty-four rabbits were randomly assigned to three groups: group 1 (n=18, sham operation), group 2 (n=18, 30 min of normothermic aortic cross-clamping) and group 3 (n=18, aprikalim 100 mg/kg was administered 15 min before 30 min of normothermic aortic cross-clamping). Neurologic evaluation was performed according to the modified Tarlov scale. Six animals from each group were sacrificed at 24, 48 and 168 h postoperatively. The lumbar spinal cords were harvested and examined histologically. The motor neurons were counted and the histologic lesions were scored (0-3, 3: normal). Results: Group 3 (aprikalim group) had better Tarlov scores compared to group 2 at all-time points (P &lt; 0.025). The histologic changes were proportional to the Tarlov scores and group 3 had better functional outcome as compared to group 2 at 168 h (number of neurons: 21.2 4.9 vs. 8.0 ± 2.7, P &lt; 0.001 and histologic score: 1.67 ± 1.03 vs. 0.50 ± 0.55, P=0.03). Although aprikalim exhibited improved effect on clinical and histologic neurologic outcome when compared to normothermic spinal cord ischemia, animals in group 3 had worse Tarlov score, reduced number of motor neurons and worse histologic score when compared to group 1 (sham operation) at 168 h (P=0.003, P=0.001 and P=0.019 respectively). Conclusions: Aprikalim reduces the severity of spinal cord ischemic injury in a rabbit model of spinal cord ischemia