Resolving the location of small intracontinental earthquakes using Open Access seismic and geodetic data: lessons from the 18 January 2017 mb 4.3, Niger, earthquake

A low-magnitude earthquake was recorded on January 18, 2017, in the T\'{e}n\'{e}r\'{e} desert in Niger. This intraplate region is exceptionally sparsely covered with seismic stations and the closest open seismic station, G.TAM in Algeria at a distance of approximately 600 km, was unusually and unfortunately not operational at the time of the event. Body-wave magnitude estimates range from $m_b 4.2$ to $m_b 4.6$ and both seismic location and magnitude constraints are dominated by stations at teleseismic distances. The seismic constraints are strengthened considerably by array stations of the International Monitoring System for verifying compliance with the Comprehensive Nuclear Test-Ban-Treaty. This event, with magnitude relevant to low-yield nuclear tests, provides a valuable validation of the detection and location procedure for small land-based seismic disturbances at significant distances. For seismologists not in the CTBT system, the event is problematic as data from many of the key stations are not openly available. We examine the uncertainty in published routinely-determined epicenters by performing multiple Bayesloc location estimates with published arrival times considering both all published arrival times and those from open stations only. This location exercise confirms lateral uncertainties in seismologically-derived location no smaller than 10 km. Coherence for InSAR in this region is exceptionally high, and allows us to confidently detect a displacement of the order 6 mm in the time-frame containing the earthquake, consistent with the seismic location estimates, and with a lateral length scale consistent with an earthquake of this size, allowing location constraint to within one rupture length ($\leq 5$ km) -- significantly reducing the lateral uncertainty compared with relying on seismological data only. Combining Open Access-only seismological and geodetic data, we precisely constrain the source location, and conclude that this earthquake likely had a shallow source. We then discuss potential ways to continue the integration of geodetic data in the calibration of seismological earthquake location.

Pakistan and the Nuclear Non-Proliferation Regime

The arrival of nuclear weapons was detrimental in changing the nature of warfare; duringWWII, we used nuclear weapons on two Japanese cities. The catastrophic effect of nuclear weapons made the pioneers apprehensive about the spread of nuclear technology across the globe. The Nuclear Non-Proliferation Regime (NNPR) is a set of international rules, norms, initiatives, agreements, arrangements, bilateral and multilateral treaties to curb the spread of nuclear weapons and technology. The Nuclear Non-Proliferation Treaty (NPT) is the backbone of NNPR. This paper discusses the significance of NNPR and will focus on how Pakistan fits into the bigger picture of the NNPR as a nuclear state. This research study will further analyze the prospects and challenges for Pakistan viz a viz the NNPR. It will specifically focus on Pakistan's official position on joining the Nuclear Non-Proliferation Treaty (NPT), Comprehensive Test Ban Treaty (CTBT), Fissile Material Cut-off Treaty (FMCT), and the two relevant Export Control Regimes (Nuclear Suppliers Group and Missile Technology Control Regime). Moreover, the challenges Pakistan faces viz-a-viz these treaties and arrangements will be highlighted. Recommendations will be provided based on the prospects of how Pakistan can overcome these challenges.

Applying Waveform Correlation to Reduce Seismic Analyst Workload Due to Repeating Mining Blasts

ABSTRACT Agencies that monitor for underground nuclear tests are interested in techniques that automatically characterize mining blasts to reduce the human analyst effort required to produce high-quality event bulletins. Waveform correlation is effective in finding similar waveforms from repeating seismic events, including mining blasts. We report the results of an experiment to detect and identify mining blasts for two regions, Wyoming (U.S.A.) and Scandinavia, using waveform templates recorded by multiple International Monitoring System stations of the Preparatory Commission for the Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO PrepCom) for up to 10 yr prior to the time of interest. We discuss approaches for template selection, threshold setting, and event detection that are specialized for characterizing mining blasts using a sparse, global network. We apply the approaches to one week of data for each of the two regions to evaluate the potential for establishing a set of standards for waveform correlation processing of mining blasts that can be generally applied to operational monitoring systems with a sparse network. We compare candidate events detected with our processing methods to the Reviewed Event Bulletin of the International Data Centre to assess potential reduction in analyst workload.

Infrasound Thunder Detections across 15 Years over Ivory Coast: Localization, Propagation, and Link with the Stratospheric Semi-Annual Oscillation

Every day, about one thousand thunderstorms occur around the world, producing about 45 lightning flashes per second. One prominent infrasound station of the International Monitoring System infrasound network of the Comprehensive Nuclear-Test-Ban Treaty Organization for studying lightning activity is in Ivory Coast, where the lightning rate of this region is relatively high. Infrasound defines acoustic waves with frequencies below 20 Hz, the lower limit of human hearing. Statistical results are presented in this paper based on infrasound measurements from 2004 to 2019. One-to-one association between infrasound detections from 0.5 to 5 Hz and lightning flashes detected by the World Wide Lightning Location Network within 500 km from the infrasound station is systematically investigated. Most of the infrasound signals detected at IS17 in this frequency band are due to thunder, even if the thunderstorms are located up to 500 km away from the station. A decay of the thunder amplitude with the flash distance, d, is found to scale as d−0.717 for flashes within 100 km from the station, which holds for direct propagation. Interestingly, the stratospheric detections reflect a pattern in the annual azimuth variation, which is consistent with the equatorial stratospheric semi-annual oscillation.

The Comprehensive Nuclear Test-Ban Treaty, a legal anomaly?

It is well-recorded that nuclear attacks happened twice in history, in Hiroshima and Nagasaki, but it is often overlooked that nuclear explosions were more frequent, with over 2,000 tests taking place in more than 60 locations worldwide. These special circumstances prompted the General Assembly to adopt a comprehensive ban treaty (CTBT) in 1996, which has yet to enter into force. Borrowing from Kelman’s social conformity theory, this article explains how and why states chose to conform to a non-binding agreement. It argues that, as interested parties developed an anti-testing narrative that seemed simultaneously hopeful and realistic, they stabilized actor’s reaction and catalyzed a shift in attitudes towards nuclear testing from forbearance to an authoritative global moratorium, which accounts for the complete eradication of the atmospheric experiments. C’est un fait bien établi que l’histoire a connu deux attaques nucléaires, à Hiroshima et Nagasaki. Ce que l’on sait moins, c’est que les explosions nucléaires étaient bien plus fréquentes, avec plus de 2 000 tests effectués sur une soixantaine de sites de par le monde. Ces circonstances particulières ont poussé l’Assemblée générale des Nations unies à adopter, en 1996, un traité d’interdiction complète des essais nucléaires (TICE), qui n’est pas encore entré en vigueur. S’inspirant de la théorie du conformisme social de Kelman, cet article explique comment et pourquoi des États ont choisi de respecter un accord non contraignant. Il avance que, à mesure que les parties intéressées développaient un discours anti-essais nucléaires qui paraissait à la fois réaliste et porteur d’espoir, elles ont stabilisé les réactions des acteurs et déclenché un changement des mentalités à l’égard des essais nucléaires, passant de l’indulgence à un moratoire général faisant autorité, ce qui explique la disparition complète des essais atmosphériques. Het is algemeen bekend dat er in de geschiedenis twee kernaanvallen zijn geweest, in Hiroshima en Nagasaki, maar vaak wordt over het hoofd gezien dat er nog andere kernexplosies hebben plaatsgevonden, met ruim 2000 proeven op meer dan 60 locaties over de hele wereld. Deze bijzondere omstandigheden hebben de Algemene Vergadering ertoe aangezet om in 1996 een alomvattend verbodsverdrag (CTBT) goed te keuren, dat nog steeds niet in werking is getreden. Aan de hand van de sociale-conformiteitstheorie van Kelman wordt in dit artikel uitgelegd hoe en waarom staten ervoor kiezen zich te conformeren aan een niet-bindende overeenkomst. Het betoogt dat, naarmate de betrokken partijen een narratief tegen kernproeven ontwikkelden dat tegelijk hoopvol en realistisch leek, zij de reactie van de actoren stabiliseerden en als katalysator werkten voor de verschuiving in de houding ten opzichte van kernproeven van gedoging naar een wereldwijd officieel moratorium, wat de volledige uitroeiing van de atmosferische experimenten verklaart. Está bien documentado que los ataques nucleares han sucedido dos veces en la historia, en Hiroshima y Nagasaki, pero en ocasiones pasa desapercibido que las explosiones nucleares han sido más frecuentes, con más de 2.000 ensayos llevándose a cabo en más de 60 emplazamientos a escala mundial. Estas circunstancias especiales llevaron a la Asamblea General a adoptar el tratado de prohibición completa (TPCEN) en 1996, el cual aun no ha entrado en vigor. Basándose en la teoría de la conformidad social de Kelman, este artículo explica cómo y porqué los Estados eligieron conformarse con un acuerdo no vinculante. Se argumenta que a medida que las partes interesadas desarrollaron una narrativa anti-ensayo que parecía esperanzadora y realista a la vez, ello mismo llevó a apaciguar la posible reacción de los actores y a catalizar un cambio en relación a los ensayos nucleares que fuera de la tolerancia a una moratoria global fidedigna, lo cual equivale a una completa erradicación de los experimentos atmosféricos. É ben noto che nella storia siano avvenuti due attacchi nucleari, a Hiroshima e Nagasaki, ma è spesso trascurato che le esplosioni nucleari siano state molto più frequenti, con oltre 2000 test che hanno avuto luogo in più di 60 sedi nel mondo. Queste circostanze speciali hanno indotto l'Assemblea generale nel 1996, ad adottare un trattato di messa al bando globale (CTBT), che deve ancora entrare in vigore. Prendendo spunto dalla teoria della conformità sociale di Kelman, questo articolo spiega come e perché gli Stati hanno scelto di conformarsi a un accordo non vincolante. Sostiene che, dato che le parti interessate hanno sviluppato una narrativa anti-test che sembrava allo stesso tempo speranzosa e realistica, esse hanno stabilizzato la reazione degli attori e catalizzato un cambiamento negli atteggiamenti nei confronti dei test nucleari dalla tolleranza a un'autorevole moratoria globale, che spiega la completa eliminazione degli esperimenti atmosferici. Es ist bekannt, dass es in der Geschichte zweimal zu nuklearen Angriffen kam, in Hiroshima und Nagasaki. Es wird aber oft übersehen, dass es häufiger nukleare Explosionen gegeben hat, mit über 2.000 Tests an mehr als 60 Orten weltweit. Diese besonderen Umstände veranlassten die Generalversammlung 1996 zur Verabschiedung eines umfassenden Verbotsvertrags (CTBT), der noch nicht in Kraft getreten ist. In Anlehnung an die soziale Konformitätstheorie von Kelman erklärt dieser Artikel, wie und warum Staaten sich dafür entschieden haben, sich einem unverbindlichen Abkommen zu fügen. Er argumentiert, dass je nachdem die beteiligten Parteien ein Anti-Test-Narrativ entwickelten, das gleichzeitig hoffnungsvoll und realistisch erschien, diese die Reaktion der Akteure stabilisierten und eine Verschiebung in der Haltung gegenüber Atomtests von der Duldung zu einem autoritativen globalen Moratorium herbeiführten, was die vollständige Abschaffung der atmosphärischen Experimente erklärt.