Seismological Research Letters Volume 79, Number 1 January/February 2008 119 INTRODUCTION A shallow moderate earthquake of MN (Nuttli magnitude) 4.1 occurred near Sudbury, Ontario, at 07:22:55 UTC (02:22:55 local time) on 29 November 2006. Te event was located 6 km from Lively, Ontario, and was induced by mining activ- ity at Inco’s Creighton mine. Inco’s in-mine monitoring sys- tem, and its subsequent visual inspection, places the event at 46.478 N 81.203 W, at a depth of 2.35 km. Tis event ofers us a rare close-up view of a moderate earthquake, because it was recorded at close distances by fve three-component broad- band POLARIS (Portable Observatories for Lithospheric Analysis and Research Investigating Seismicity; http://www. polarisnet.ca) seismographic stations that are installed above and within the Creighton mine. Two stations are located on the surface, near the epicenter, while three subsurface stations are at depths of 1 to 2 km. Te closest station to the event is within the Sudbury Neutrino Observatory (SNO) lab, which is 2 km beneath the surface and about 300 m above the event. Te event caused no damage to the SNO lab and only minor dam- age to the mine workings; there were no injuries. Te event was widely felt in the Sudbury, Ontario, region, as expected based on instrumental ShakeMaps (http://www.shakemap.carleton. ca) and confrmed by Internet intensity reports (http://www. earthquakescanada.ca). Te mainshock was followed by two signifcant afershocks at 2:36 (MN 2.0) and 2:38 (MN 3.1) local time and by many smaller afershocks. In addition to the near-source records, this event was well-recorded regionally at distances from 20 km to hundreds of kilometers by the seis- mographic stations of the Canadian National Seismographic Network (CNSN) and POLARIS. Figure 1 shows the location of the Lively event in relation to regional seismographic sta- tions; the nearest regional station is SUNO, 22 km away. In this paper we provide a preliminary examination of the recorded ground motions from this event and discuss their implications for our understanding of source and attenuation properties in eastern North America (ENA). TECTONIC SETTING AND EARTHQUAKE SEQUENCE Tectonic Setting One of the world’s deepest underground mines ( > 2 km), the Creighton mine has produced more than 160 metric tons of nickel-copper ore since opening in 1901. Te mine is located along the southern periphery of the Sudbury Structure, inter- preted by most researchers as a relict giant impact (e.g., Riller 2005; Grieve and Terriault 2000). Te structure consists of a diferentiated melt sheet (Sudbury Igneous Complex) overlain by impact breccias and post-impact sedimentary rocks (Pye et al. 1984). Te structure, together with older Precambrian rocks of the Canadian Shield, was deformed by post-impact orogenic processes to produce a large-scale asymmetric syn- form (Milkereit et al. 1992). Like most other ore deposits in the Sudbury region, the Creighton Mine is situated near the base of the impact melt sheet, near its contact with the footwall. Te SNO laboratory, where the closest seismic instruments are located, is situated within a massive igneous unit (norite) within the Sudbury Igneous Complex. The Lively Sequence Te Lively earthquake sequence consisted of the MN 4.1 main- shock and a sequence of afershocks. Accurate characterization of afershock statistics is important for hazard calculations, par- ticularly in a mining environment where they may determine EASTERN SECTION RESEARCH LETTERS A Very Close Look at a Moderate Earthquake near Sudbury, Ontario Gail M. Atkinson, SanLinn I. Kaka, David Eaton, Allison Bent, Veronika Peci, and Stephen Halchuk Gail M. Atkinson, 1 SanLinn I. Kaka, 2 David Eaton, 3 Allison Bent, 4 Veronika Peci, 4 and Stephen Halchuk 4 1. University of Western Ontario, London, Ont. 2. King Fahd University, Saudi Arabia 3. University of Calgary, Alberta 4. Geological Survey of Canada, Ottawa