How do earth tides affect astronomers?

Earth tides affect astronomical observations of the Earth's rotation in the following two ways: (1) verticals are deflected; and (2) the polar moment of inertia of the Earth is changed causing periodic variations in the rotation rate. The diurnal and semidiurnal tides and nutation were examined in periodic variations. Results indicate little change occured in the polar motions. Nutation observations were disturbed rather seriously by the diurnal tides

Rotation of the earth and polar motion, services

The services providing polar motion and universal time data are described. The precision and accuracy of these data are estimated

The 1909 Taipei earthquake—implication for seismic hazard in Taipei

The 1909 April 14 Taiwan earthquake caused significant damage in Taipei. Most of the information on this earthquake available until now is from the written reports on its macro-seismic effects and from seismic station bulletins. In view of the importance of this event for assessing the shaking hazard in the present-day Taipei, we collected historical seismograms and station bulletins of this event and investigated them in conjunction with other seismological data. We compared the observed seismograms with those from recent earthquakes in similar tectonic environments to characterize the 1909 earthquake. Despite the inevitably large uncertainties associated with old data, we conclude that the 1909 Taipei earthquake is a relatively deep (50–100 km) intraplate earthquake that occurred within the subducting Philippine Sea Plate beneath Taipei with an estimated M_W of 7 ± 0.3. Some intraplate events elsewhere in the world are enriched in high-frequency energy and the resulting ground motions can be very strong. Thus, despite its relatively large depth and a moderately large magnitude, it would be prudent to review the safety of the existing structures in Taipei against large intraplate earthquakes like the 1909 Taipei earthquake

Studies of water storage and other contributions to changes in the rotation of the Earth

The effects were determined of the global redistribution of water mass on various geodetic observables, especially polar motion, and complementary observables such as geodetic satellite positions. The effect of water mass redistribution has been and continues to be less well known and more difficult to observe than effects of air mass distribution, yet the water contribution is potentially significant over a large range of periods. The current understanding is reviewed of the contribution of polar drift, decadal polar motion, Chandler and annual wobbles, and higher frequency polar motion, as determined through the efforts of the funded work within the NASA Crustal Dynamics Project, and in the context of the general literature on the subject. Water mass redistribution is either demonstrably important to the excitation of each of these, or is probably important given a lack of other likely excitation sources

The East-Asian VLBI Network

The East-Asian VLBI Network (EAVN) is the international VLBI facility in East Asia and is conducted in collaboration with China, Japan, and Korea. The EAVN consists of VLBI arrays operated in each East Asian country, containing 21 radio telescopes and three correlators. The EAVN will be mainly operated at 6.7 (C-band), 8 (X-band), 22 (K-band), and 43 GHz (Q-band), although the EAVN has an ability to conduct observations at 1.6 - 129 GHz. We have conducted fringe test observations eight times to date at 8 and 22 GHz and fringes have been successfully detected at both frequencies. We have also conducted science commissioning observations of 6.7 GHz methanol masers in massive star-forming regions. The EAVN will be operational from the second half of 2017, providing complementary results with the FAST on AGNs, massive star-forming regions, and evolved stars with high angular resolution at cm- to mm-wavelengths.Comment: 6 pages, 3 figures, 2 tables. To appear in the proceedings of "Frontiers in Radio Astronomy and FAST Early Sciences Symposium 2015" ed. Lei Qian (ASP Conf. Ser.

Supplement zur Geschichte der Bibliothek des Astronomischen Rechen-Instituts

Als Ergänzung zum Hauptteil der Geschichte der Bibliothek des Astronomischen Rechen-Instituts (Wielen, R., Wielen, U., Hefele, H., Heinrich, I. 2014a) geben wir hier Scans von einigen relevanten Archivalien wieder. Ferner listen wir die Sternwarten-Veröffentlichungen in der Institutsbibliothek auf

Historical seismograms for unravelling a mysterious earthquake: The 1907 Sumatra Earthquake

History of instrumental seismology is short. Seismograms are available only for a little more than 100 years; high-quality seismograms are available only for the last 50 years and the seismological database is very limited in time. To extend the database, seismograms of old events are of vital importance. Many unusual earthquakes are known to have occurred, but their seismological characteristics are poorly known. The 1907 Sumatra earthquake is one of them (1907 January 4, M= 7.6). Gutenberg and Richter located this event in the outer-rise area of the Sunda arc. This earthquake is known to be anomalous because of its extensive tsunami, which is disproportionate of its magnitude. The tsunami affected the coastal areas over 950 km along the Sumatran coast. We investigated this earthquake using the historical seismograms we could collect from several seismological observatories. We examined the P-wave arrival times listed in the Strassburg Bulletin (1912) and other station bulletins. The scatter of the Observed−Computed traveltime residuals ranges from –30 to 30 s, too large to locate the event accurately. The uncertainty of the epicentre estimated from an S-P grid-search relocation study is at least 1° (~110 km). We interpreted the Omori seismograms from Osaka, Mizusawa and Tokyo, and the Wiechert seismograms from Göttingen and Uppsala by comparing them with the seismograms simulated from modern broad-band seismograms of the 2002, 2008 and two 2010 Sumatra earthquakes which occurred near the 1907 earthquake. From the amplitude of Rayleigh waves recorded on the Omori seismograms we conclude that the magnitude of the 1907 earthquake at about 30 to 40 s is about 7.8 (i.e. 7.5 to 8.0). The SH waveforms recorded on the Göttingen and Uppsala seismograms suggest that the 1907 earthquake is a thrust earthquake at a shallow depth around 30 km. The most likely scenario is that the 1907 earthquake initiated on the subduction interface, and slowly ruptured up-dip into the shallow sediments and caused the extensive tsunami. Although their quantity and quality are limited, historical seismograms provide key quantitative information about old events that cannot be obtained otherwise. This underscores the importance of preserving historical seismograms

NASA space geodesy program: Catalogue of site information

This is the first edition of the NASA Space Geodesy Program: Catalogue of Site Information. This catalogue supersedes all previous versions of the Crustal Dynamics Project: Catalogue of Site Information, last published in May 1989. This document is prepared under the direction of the Space Geodesy and Altimetry Projects Office (SGAPO), Code 920.1, Goddard Space Flight Center. SGAPO has assumed the responsibilities of the Crustal Dynamics Project, which officially ended December 31, 1991. The catalog contains information on all NASA supported sites as well as sites from cooperating international partners. This catalog is designed to provde descriptions and occupation histories of high-accuracy geodetic measuring sites employing space-related techniques. The emphasis of the catalog has been in the past, and continues to be with this edition, station information for facilities and remote locations utilizing the Satellite Laser Ranging (SLR), Lunar Laser Ranging (LLR), and Very Long Baseline Interferometry (VLBI) techniques. With the proliferation of high-quality Global Positioning System (GPS) receivers and Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS) transponders, many co-located at established SLR and VLBI observatories, the requirement for accurate station and localized survey information for an ever broadening base of scientists and engineers has been recognized. It is our objective to provide accurate station information to scientific groups interested in these facilities

Analysis of latitude observations for detection of crustal movements

Analysis of latitude observations for detection of earth crust movement