Earthquake location inverse problem: a review and an application to the aftershocks of the Southern Italy 23 November 1980 earthquake

Summary In the last few years many improvements have been realized on the application of inverse methods to seismology. Increasing attention has been payed to simulataneous inversion methods, allowing us to determine hypocentral parameters and velocity models using data from a set of earthquakes recorded by dense seismic arrays. Since the first studies by Peters and Crosson, Crosson and Aki and Lee, recently Thurber, Pavlis, Spencer-Gubbins developed new techniques which are more efficient and practicable also with moderate-size computers. In the first part of this paper a review of all these recent inversion methods in presented starting with the simple location algorithms, to come to the most sophisticated simultaneous inversion methods. For shortness the discussion is restricted to the so-called ?overdetermined? problem in which the velocity model is parametrized by a finite number of parameters. A brief appendix about the most powerful mathematical inversion techniques is also presented. In the second part, we present a study on the precision and the accuracy of some location algorithms, used to relocate aftershocks by using a temporary seismic array installed soon after the 1980 Southern Italy earthquake. This study remarks the important role of network geometry and the use of accurate algorithms for identifying earthquakes rupture zones.

---

Riassunto Negli ultimi anni è stato dato un forte impulso all'applicazione dei metodi di inversione alla sismologia. Particolare attenzione è stata posta nei metodi di ?inversione simultanea? che permettono di determinare parametri ipocentrali e modelli di velocità usando i dati provenienti da insiemi di terremoti registrati da fitte reti locali. I primi studi in questo campo si denovo a Peters e Crosson, Crosson ed Aki e Lee. Recentemente Spencer e Gubbins, Thurber e Pavlis hanno sviluppato nuove tecniche che sono piú efficienti e praticabili anche con piccoli calcolatori. Nella prima parte di questo articolo presentiamo un'esposizione dei piú recenti metodi d'inversione iniziando dai moderni algoritmi di localizzazione per arrivare ai piú sofisticati metodi di inversione simultanea. Per brevità la nostra discussione sarà ristretta al cosiddetto ?problema sovradeterminato? in cui il modello di velocità è specificato mediante un numero finito di parametri. In appendice è contenuta una breve introduzione sulle piú efficaci tecniche matematiche d'inversione. Nella seconda parte, presentiamo uno studio sulla precisione ed attendibilità degli algoritmi di localizzazione usati per localizzare le repliche del terremoto irpino-lucano del 1980, registrate con una rete sismica locale installata poco tempo dopo l'evento principale. Questo studio sottolinea il ruolo importante che una buona geometria della rete e l'uso di accurati algoritmi d'inversione rivestono nell'identificazione delle zone di rottura associate ad eventi sismici.

---

Резюме В последние несколько лет были реализованы различные улучшения методов решения обратной проблемы сейсмологии. Особое внимание уделяется методам одновременной инверсии, позволяющим определить параметры гипоцентра, и скоростным моделям, использующим данные системы землетрясений, зарегистрированных с помощью плотных сейсмических цепочек. Со времени первых исследований Питерса и Кроссона, Кроссона и Аки и Ли, недавно были предложены =qnовые методики Турбером, Паулисом, Спенсером-Губинсом, которые являются более эффективными, а также используют компьютеры средних размеров. В первой части этой работы предлагается обзор всех методов инверсии, начиная с простых алгоритмов локализации и переходя к наиболее сложным методам одновременной инверсии. Рассмотрение ограничено так называемой ?переопределенной? проблемой, где скоростная модель параметризуется с помощью конечного числа параметров. В приложении приведены наиболее мощные математические методы инверсии. Во второй части проводится анализ точности некоторых алгоритмов локализации, которые применяются для повторной локализации последующих толчков, используя временную сейсмическую систему, установленную вскоре после землетрясения 1980 г. в Южной Италии. Отмечается важная роль геометрии пространственной структуры и использования точных алгоритмов для идентификации землетрясений в зонах разлома.

     

Surface conductance and film concentration potential

Summary A simple method for determining the film concentration potential (FCP) is described.The FCP appears when the film specific conductance (k _f ⁰ ) < 10^–7 ohms^–1.The FCP increases with decreasing values of the (k _f ⁰ ), reaching to a maximum at (k _f ⁰ ) k(k _s ⁰ ).

---

Zusammenfassung Eine einfache Methode für die Bestimmung des Filmkonzentrations-Potentials (FCP) wird beschrieben. Das FCP tritt auf, wenn die spezifische Leitfähigkeit des Films kleiner als 10^{–7 –1} wird.Das Filmkonzentrationspotential steigt mit abnehmenden Werten der spezifischen Filmleitfähigkeit und erreicht ein Maximum für die Annäherung an gleichgroße Werte für ihre spezifische Oberflächenleitfähigkeit.

     

Regioselectivity in lateral deprotonation of an isoxazolecarboxamide of (S)-prolinol. Conformational correlation by crystal structure solid state solution 13C NMR

The conformation at the amide functional group in 3,5-dimethylisoxazole-4-(S-2′-hydroxymethyl-N-pyrrolidino) carboxamide (1) has been determined by a single crystal X-ray determination. The ¹³C nmr in both deuteriochloroform solution and solid state show close agreement. The metalation behaviour of the amide is dependent upon the substitution on the 2′-hydroxymethyl moiety. Dianion studies indicate C-5 lateral metalation under both thermodynamic and kinetic conditions. Protection of this substituent as the methyl ether, 2 , gives rise to predominant C-3 lateral metalation under kinetic conditions and C-5 lateral metalation on equilibration. These observations can be explained using the Ireland-Evans model for chelation directed deprotonation.     

Pulselike Exact Solutions for a Model Describing Nerve Fibers

A quasi-linear nonhomogeneous first order hyperbolic system describing nerve pulse transmission is considered. By requiring the compatibility of the governing equations with quasi-linear differential constraints, exact solutions to the model in question are determined. Furthermore classes of material response functions amenable to the mathematical approach are characterized. Initial and/or boundary value problems of interest in nerve pulse propagation are solved. It is proved that the governing model admits solutions which describe a space clamp situation and the propagation of a localized action potential pulse along the nerve.     

High performance liquid chromatography-tandem mass spectrometry of phospholipid molecular species in eggs from hens fed diets enriched in seal blubber oil

The total lipid fraction of eggs from hens fed diets enriched in seal blubber oil (1.25-5.0% SBO) was directly analysed with normal-phase high performance liquid chromatography coupled on-line with electrospray ionization ion-trap tandem mass spectrometry (HPLC-ESI-MS-MS) for the identification of the molecular species of phospholipids (PLs). The species of phosphatidylethanolamine (PE) and phosphatidylinositol (PI) were all detected as the [M-H](-) ions. The phosphatidylcholine (PC), sphingomyelin (Sph) and lysophosphatidylcholine (LPC) classes, were detected as formate adducts [M+HCOO](-). Tandem MS of PE and PI showed the loss of the carboxylate anions, and, for PI, also the loss of water and inositol. Product ion spectrum of PC, LPC and Sph contained only the [M-CH(3)](-) ion fragment. Feeding different levels of SBO for 5 weeks resulted in a significant increase of PE, PC and PI molecular species carrying eicosapentaenoic acid (C(20:5 omega3), EPA), docosapentaenoic acid (C(22:5 omega3), DPA) and docosahexaenoic acid (C(22:6 omega3), DHA), but not Sph nor LPC. The highest increase of the omega3/omega6 ratio occurred for PE and PC. On the contrary, PI was less affected by the increase of SBO in the diet.     

Absolute frequency measurements of the 2(3)S1-->2(3)P 0,1,2 atomic helium transitions around 1083 nm

We measure the frequency of the 2(3)S1-->2(3)P(0,1,2) transitions of helium in a metastable beam using an optical frequency comb synthesizer. The relative uncertainty of these measurements ranging from 5x10(-11) to 7x10(-12) is, to our knowledge, the most precise result for any optical helium transition. Considering existing accurate values of the 2(3)P fine structure, we measure a centroid value of the 2(3)S-2(3)P frequency of 276 736 495 624.6(2.4) kHz, improving the previous interferometric measurement by 30 times. New accurate values of the 2(3)S-2(3)P and 2(3)P Lamb-shift energies are obtained.