Mechanism on Moho offset induced by aseismic slip of deeply buried faults

Recent high-resolution deep seismic reflection profile across the Kunlun fault in northeastern Tibet shows clearly that the Moho is cut off by a complex thrust fault system. Moho offset is a general phenomenon, but little is known about the dynamic mechanism. In this study, contact models with Maxwell materials are used to simulate the mechanical process of Moho offset induced by the aseismic slip of deeply buried faults. Based on the seismic reflection data, we project a single fault model and a complex fault system model with two faults inter- secting. The deformations of the Moho, the aseismic slips, and contact stresses on faults in different models are discussed in detail. Results show that the Moho offset might be produced by aseismic slip of deeply buried faults, and the magnitude is influenced by the friction coefficient of faults and the viscosity of the lower crust. The maximum slip occurs near the Moho on the single fault or at the crossing point of two intersecting faults system. Stress concentrates mainly on the Moho, the deep end of faults, or the crossing point. This study will throw light on understanding the mechanism of Moho offset and aseismic slip of deeply buried faults. The results of complex fault system with two faults intersecting are also useful to understand the shallow intersecting faults that may cause earthquakes.

Isolated interrupted aortic arch in an adult:A case report

BACKGROUND Interrupted aortic arch(IAA)is a rare congenital heart disease defined by an interruption of the lumen and anatomical continuity between the ascending and descending major arteries.It is usually found within a few hours or days of birth.Without surgery,the chances of survival are low.If IAA patients have an effective collateral circulation established,they can survive into adulthood.However,IAA in adults is extremely rare,with few reported cases.CASE SUMMARY A 27-year-old woman presented with a 6-year history of progressively worsening shortness of breath and chest tightness on exertion.She had cyanotic lips and clubbing of the fingers.A transthoracic echocardiogram revealed an enlarged heart and dilation of the main pulmonary artery.There was an abnormal 9 mm passage between the descending aorta and pulmonary artery.The ventricular septal outflow tract had a 14 mm defect.Doppler ultrasound suggested a patent ductus arteriosus and computed tomographic angiography showed the absence of the aortic arch.The diagnoses were ventricular septal defect,patent ductus arteriosus,and definite interruption of the aortic arch.Although surgical correction was recommended,the patient declined due to the surgical risks and was treated with medications to reduce pulmonary artery pressure and treat heart failure.Her condition has been stable for 12 mo of follow-up.CONCLUSION Although rare,IAA should be considered in adults with refractory hypertension or unexplained congestive heart failure.