A STUDY OF NEW ENGLAND SEISMICITY

Quarterly Earthquake Report
April-June, 2004

Weston Observatory

381 Concord Road

Weston, MA 02493

Network operation supported by the U.S. Geological Survey (USGS), Department of the Interior, under USGS award number 04HQAG0020. The views and conclusions contained in this document are those of the authors andshould not be interpreted as necessarily representing the official policies,either expressed or implied, of the U.S. Government.

• Introduction
• Current Network Operationand Status
• Seismicity
• Data Management
• Tables
• Explanation of Tables
• Table 1 Project Personnel
• Table 2 Seismic Stations
• Table 3 Earthquake Hypocenter List
• Table 4 Earthquake Phase Data List
• Table 5 Microearthquakes and Other Non-locatable Events
• Figures
• NESN Station Map
• NESN Strong-Motion Station Map
• NESN Quarterly Seismicity Map
• NESN Cumulative Seismicity Map
• Acknowledgments
• References

Introduction

The New England Seismic Network (NESN) is operated by the Weston Observatory (WES) of Boston College. The mission of the NESN is to operate and maintain a regional seismic network with digital recording of seismic ground motions for the following purposes: 1) to determine the location and magnitude of earthquakes in and adjacent to New England and report felt events to public safety agencies, 2) to define the crust and upper mantle structure ofthe northeastern United States, 3) to derive the source parameters of New England earthquakes, and 4) to estimate the seismic hazard in the area.

This report summarizes the work of the NESN for the period April-June, 2004. It includes a brief summary of the network's equipment and operation, and a short discussion of data management procedures. A list of participating personnel is given in Table 1. There were 2 earthquakes that occurred within or near the network during this reporting period. Phase information for these earthquakes is included in this report.

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Current Network Operation and Status

The New England Seismic Network of Weston Observatory of Boston College currently consists of 11 broadband three-component and 8 analog strong-motion stations. The coordinates of the stations are given in Table 2, and maps of the weak- and strong-motion networks are shown in Figures 1 and 2, respectively. The 11 stations consist of Guralp CMG-40T three-component sensors. Ground motions recorded by these sensors are digitized at 100 sps with 16-bit resolution. Additional gain-ranging provides 126 dB dynamic range. These stations are operated in dialup mode with waveform segments of suspected events transmitted in digital mode to Weston Observatory for analysis and archiving. WES also maintains 8 SMA-1 strong-motion instruments in New England.

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Seismicity

There were 2 earthquakes that occurred in or adjacent to the NESN during this reporting period. A summary of the location data is given in Table 3. Figure 3 shows the locations of these events. Figure 4 shows the locations of all events since the beginning of network operation in October, 1975.

Table 4 gives the station phase data and detailed hypocenter data for each event listed in Table 3. In addition to NESN data, arrival time and magnitude data sometimes are contributed for seismic stations operated by the Geological Survey of Canada (GSC), the Lamont-Doherty Cooperative Seismographic Network, and the US National Seismic Network. Final locations for this section were computed using the program HYPO78. For regional events (those too far from the NESN to obtain accurate locations and magnitudes) phase data are given for NESN stations, but the entry in Table 3 lists the hypocenter and geographic location information adopted from the authoritative network. Accordingly, the epicenter is plotted on the maps using the entry from Table 3.

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Data Management

Recent event locations are available at http://aki.bc.edu/cgi-bin/NESN/recent_events.pl. Waveform data are saved in Nanometrics, ASCII, and SEED formats and are available by contacting, Anastasia Macherides Moulis, via email. Earthquake lists can be found at www.bc.edu/research/westonobservatory/northeast/eqcatalogs/. Currently available on the Weston Observatory web page is the full catalog of northeastern U.S. earthquake activity to the present time. This will be updated as new Northeastern U.S. Seismic Network Quarterly Earthquake Reports are produced.

For more information on matters discussed in this report or general earthquake information (reports, maps, catalogs, etc.) consult our web site www.bc.edu/westonobservatory or contact:

Voice: 617-552-8325 / FAX: 617-552-8388 / Email: anastasia.macherides.1@bc.edu

Voice: 617-552-8335 / FAX: 617-552-8388 / Email: dina.smith.1@bc.edu

Voice: 617-552-8319 / FAX: 617-552-8388 / Email: ebel@bc.edu

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Explanation of Tables

Table 1: List of personnel operating the NESN

Table 2: List of Seismic and Strong Motion Stations

Table 3: Earthquake Hypocenter List

Table 4: Earthquake detailed hypocenter and phase data list

Table Header: detailed hypocenter data

Table Body: earthquake phase data

Table 5: Microearthquakes and other non-locatable events

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TABLE 5

MICROEARTHQUAKES AND OTHER NON-LOCATABLE EVENTS

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NESN Station Map

NESN Strong-Motion Station Map

NESN Quarterly Seismicity Map

NESN Cumulative Seismicity Map

Figure 4: Seismicity for period October, 1975 - June, 2004.