Network operation supported by the U.S. Geological Survey (USGS), Department of the Interior, under USGS award number 1434-HQ-98-AG-01943 and award number 1434-HQ-98-AG-01926. The views and conclusions contained in this document are those of the authors and should not be interpreted as necessarily representing the official policies, either expressed or implied, of the U.S. Government.

• Introduction
• Current Network Operation and 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 collaboratively by the Weston Observatory (WES) of Boston College and the Earth Resources Lab (ERL) of the Massachusetts Institute of Technology. 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 of the 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 July - September, 1999. 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 4 earthquakes that occurred within or near the network during this reporting period. Phase information for these earthquakes is included in this report.

Current Network Operation and Status

The New England Seismic Network currently consists of 13 broadband three-component, 4 short-period vertical, and 8 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.

WES operates 12 stations with broadband instruments consisting 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 is continuing to upgrade its recording stations with 2 more broadband instruments scheduled for installation in 2000. WES also maintains 8 SMA-1 strong-motion instruments in New England.

ERL at MIT currently operates 4 short-period stations, all located within 100 km of Boston. The short- period instruments have 1.0 Hz L4C vertical seismometers. Data recorded by these seismometers is transmitted continuously in analog mode to ERL and digitized (12-bit) into a PC at 50 sps. A data acquisition program on the PC triggers on events detected in the short-period data streams and saves them to a disk for manual analysis. Station WFM also has a new three-component, high dynamic range instrument. The instrument has a CMG-40T sensor and transmits 3-channel, 24-bit data at 100 sps continuously to a central processor (Pentium PC) at ERL. Waveform windows of suspected events are extracted from the data stream, analyzed and archived with the short-period data. WES and ERL record some stations in analog format on helicorders to provide additional data for analysis.

Seismicity

There were 4 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.

Data Management

Recent event locations are available via FTP at: SEISMOEAGLE.BC.EDU. Waveform data are saved in Nanometrics, ASCII, and SEED formats and are available via SEISMOEAGLE.BC.EDU or through personal contact. Earthquake lists can be fingered at QUAKE@SEISMOEAGLE.BC.EDU. Weston Observatory maintains two web pages with information about local earthquakes: "http://www.bc.edu:80/bc_org/avp/cas/wesobs/" and "http://seismoeagle.bc.edu/". The latter page is still under contruction. Currently available on the seismoeagle web page is the full catalog of northeastern U.S. earthquake activity to 1992. This will be updated as new Northeastern U.S. Seismic Network Bulletins are produced.

MIT/ERL provides two internet utilities, the MIT/ERL web-site ("www-erl.mit.edu/NESN/homepage.html") and an anonymous FTP directory, to distribute seismic data. SESAME (Seismic Event Server at MIT/ERL) is the web data server that distributes catalogs, reports, earthquake bulletins, and epicenter and station maps (including an archive of recent seismic events). The FTP site, named "sunda.mit.edu", is the current facility available to download waveform data recorded by the MIT NESN. The client machine IP number must be forwarded to us for the client to gain access to the anonymous FTP directory. After logging on, the user changes directories to "pub/seismic". Waveforms of individual events for the period April 1995 through the present are accessed as Unix-compressed SAC files, through the anonymous FTP directory. A "readme" file offers further explanation about the data. Older waveform data in SAC format (1981 - March 1995) will be made available on the FTP site upon request.

For more information on matters discussed in this report or general earthquake information (reports, maps, catalogs, etc.) consult our web-sites www-erl.mit.edu/NESN and www.bc.edu:80/bc_org/avp/cas/wesobs/ or contact:

Voice: 617-253-7863 / FAX: 617-253-6385 / Email: doll@erl.mit.edu

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

Explanation of Tables

Table 1: List of personnel operating the NESN

Table 2: List of Seismic and Strong Motion Stations

1. Code = station name
2. Lat = station latitude, degrees north
3. Long = station longitude, degrees west
4. Elev = station elevation in meters
5. Location = geographic location
6. Operator = network operator

Table 3: Earthquake Hypocenter List

1. Date = date event occurred, Yr (year)/Mo (month)/Dy (day)
2. Time = origin time of event, Hr (hour):Mn (minute):Sec (second)
   in UCT (Universal Coordinated Time, same as Greenwich Mean Time)
3. Lat = event location, latitude north in degrees
4. Long = event location, longitude west in degrees
5. Depth = event depth in kilometers
6. Mag = event magnitude
7. Int = event epicentral intensity
8. Location = event geographic location

Table 4: Earthquake detailed hypocenter and phase data list

Table Header: detailed hypocenter data

1. Geographic location
2. DATE = date event occurred, yr/mo/dy (year/month/day)
3. ORIGIN = event origin time (UCT) in hours, minutes, and seconds
4. LAT N = latitude north in degrees and minutes
5. LONG W = longitude west in degrees and minutes
6. DEPTH = event depth in kilometers
7. MN = Nuttli Lg phase magnitude with amplitude divided by period
8. MC = signal duration (coda) magnitude

   WES: 2.23 Log(FMP) + 0.12Log(Dist) - 2.36 (Rosario, 1979)

   MIT: 2.21 Log(FMP) - 1.7 (Chaplin et al., 1980)

9. ML = local magnitude

   WES: calculated from Wood-Anderson seismograms (Ebel, 1982)

   GSC (Geological Survey of Canada): Richter Lg magnitude

10. GAP = largest azimuthal separation, in degrees, between stations
11. RMS = root mean square error of travel time residual in seconds
12. ERH = standard error of epicenter in kilometers
13. ERZ = standard error of event depth in kilometers
14. Q = solution quality of hypocenter

    A = excellent

    B = good

    C = fair

    D = poor

Table Body: earthquake phase data

1. STN = station name
2. DIST = epicentral distance in kilometers
3. AZM = azimuthal angle in degrees measured clockwise between true north and vector pointing from epicenter to station
4. Description of onset of phase arrival

   I = impulsive

   E = emergent

5. R = phase

   P = first P arrival

   S = first S arrival

6. M = first motion direction of phase arrival

   U = up or compression

   D = down or dilatation

7. K = weight of arrival

   0 = full weight (1.0)

   1 = 0.75 weight

   2 = 0.50 weight

   3 = 0.25 weight

   4 = no weight (0.0)

8. HRMN = hour and minute of phase arrival
9. SEC = second of phase arrival
10. TCAL = calculated travel time of phase in seconds
11. RES = travel time residual (error) of phase arrival
12. WT = weight of phase used in hypocentral solution
13. AMX = peak-to-peak ground motion, in millimicrons, of the maximum envelope amplitude of vertical-component signal, corrected for system response
14. PRX = period in seconds of the signal from which amplitude was measured
15. XMAG = Nuttli magnitude recorded at station
16. FMP = signal duration (coda), in seconds, measured from first P arrival
17. FMAG = coda magnitude recorded at station

Table 5: Microearthquakes and other non-locatable events

1. Date = date event occurred, Yr (year)/Mo (month)/Dy (day)
2. Sta = nearest station recording event
3. Arrival Time = phase arrival time, Hr (hour):Mn (minute):Sec (second)

 NORTHWEST MAINE CRUSTAL STRUCTURE

 99JUL16 NB, BATHURST



  DATE     ORIGIN    LAT N    LONG W   DEPTH   MN  MC  ML GAP   RMS  ERH  ERZ Q

 990716 1455 38.31 47-28.64  65-59.48   9.91  2.8         163  0.39  1.8  3.5 C



  STN  DIST AZM  RMK HRMN   SEC   TOBS   TCAL   RES   WT AMX PRX XMAG FMP FMAG

  GSQ 180.1 332  P 2 1456  7.25  28.94  28.20  0.73 1.19

  LMN 202.2 153  P 3 1456  8.32  30.01  30.92 -0.91 0.56

                 S 0 1456 33.40  55.09  55.05  0.05 2.35

  CNQ 254.9 323  P 0 1456 15.75  37.44  37.43 -0.02 2.00

                 S 3 1456 41.89  63.58  66.63 -3.10 0.00

  A21 279.3 275  P 2 1456 19.19  40.88  40.44  0.44 0.91

  A64 295.3 278  P 0 1456 20.51  42.20  42.42 -0.24 1.72

                 S 4 1456 47.58  69.27  75.51 -6.27 0.00

  A16 302.8 270  P 3 1456 22.78  44.47  43.35  1.13 0.34

                 S 3 1456 55.59  77.28  77.16  0.12 0.42

  A61 309.3 274  P 0 1456 22.27  43.96  44.15 -0.20 1.63

  SMQ 309.7 350  P 0 1456 22.46  44.15  44.20 -0.11 1.63

                 S 2 1456 56.77  78.46  78.68 -0.33 0.81

  A11 318.6 265  P 0 1456 23.23  44.92  45.30 -0.39 1.57

  LMQ 326.8 271  P 1 1456 24.65  46.34  46.31 -0.03 1.13

                 S 3 1456 60.78  82.47  82.42 -0.08 0.38

  A54 333.2 270  P 2 1456 26.02  47.71  47.10  0.56 0.71

  MIM 341.5 223 IPD2 1456 27.16  48.85  48.13  0.71 0.68  34 .18  2.7

                 S 4 1456 76.34  98.03  85.67 12.33 0.00

  MNQ 395.7 329  P 4 1456 30.54  52.23  54.82 -2.59 0.00

                 S 3 1456 75.62  97.31  97.58 -0.27 0.26

  WVL 434.0 221 IPD1 1456 37.48  59.17  59.55 -0.39 0.59  39 .26  2.9

  DPQ 522.7 260  P 1 1456 49.03  70.72  70.50  0.22 0.14





 SOUTHEAST MAINE CRUSTAL MODEL

 99JUL27 ME, 73KM WSW OF PRESQUE ISLE



  DATE     ORIGIN    LAT N    LONG W   DEPTH   MN  MC  ML GAP   RMS  ERH  ERZ Q

 990727 1223  6.69 46-30.66  68-54.71   5.00  2.7          98  0.38  4.0  6.3 C



  STN  DIST AZM  RMK HRMN   SEC   TOBS   TCAL   RES   WT AMX PRX XMAG FMP FMAG

  A11 127.3 310  S 4 1223 39.92  33.23  36.43 -3.21 0.00

  MIM 141.2 184 IPD0 1223 29.32  22.63  22.67 -0.06 2.43 207 .14  2.8

                 S 4 1223 46.05  39.36  40.35 -1.02 0.00

  WVL 228.0 195 IPD3 1223 42.24  35.55  33.91  1.64 0.09  61 .20  2.6

                 S 4 1223 65.31  58.62  60.35 -1.75 0.00

  MOQ 291.6 243  P 1 1223 48.32  41.63  41.77 -0.27 1.14

                 S 4 1223 78.82  72.13  74.34 -2.46 0.00

  DPQ 296.8 274  P 1 1223 48.64  41.95  42.41 -0.45 1.09

                 S 4 1223 80.17  73.48  75.48 -2.00 0.00

  GSQ 299.5  27  P 3 1223 50.74  44.05  42.73  1.31 0.21

                 S 4 1223 81.52  74.83  76.07 -1.25 0.00

  CNQ 316.6  11  P 1 1223 51.98  45.29  44.85  0.41 1.03

                 S 4 1223 84.55  77.86  79.83 -2.02 0.00

  LMN 325.3 103  P 2 1223 52.33  45.64  45.92 -0.28 0.66

                 S 4 1223 88.65  81.96  81.74  0.22 0.00

 LBNH 345.5 223  P 0 1223 55.54  48.85  48.42  0.37 1.21

                 S 4 1223 92.76  86.07  86.19 -0.23 0.00

  ICQ 356.4  20  P 0 1223 56.32  49.63  49.77 -0.14 1.15

  DNH 408.0 203  S 4 1224 43.90  97.21  99.91 -2.70 0.00

  GLO 453.7 199 ES 4 1224 54.10 107.41 109.95 -2.54 0.00

  WFM 479.4 205 ES 4 1224 60.80 114.11 115.61 -1.51 0.00





 NORTHWEST MAINE CRUSTAL STRUCTURE

 99SEP10 NB, MIRAMICHI



  DATE     ORIGIN    LAT N    LONG W   DEPTH   MN  MC  ML GAP   RMS  ERH  ERZ Q

 990910 1341 45.58 47- 3.83  66- 4.89  14.99  3.0 3.1     232  0.34  3.7  4.4 C



  STN  DIST AZM  RMK HRMN   SEC   TOBS   TCAL   RES   WT AMX PRX XMAG FMP FMAG

  PQI 153.8 254 IPC0 1342 10.03  24.45  24.45 -0.02 2.11

                 S 1 1342 29.57  43.99  43.52  0.42 1.53

  GSQ 219.6 340 EP 3 1342 19.14  33.56  32.57  0.98 0.23

                 S 1 1342 43.35  57.77  57.98 -0.22 1.41

  A21 281.5 285  P 4 1342 23.76  38.18  40.22 -2.03 0.00

                 S 1 1342 56.96  71.38  71.58 -0.20 1.24

  CNQ 289.6 329  P 1 1342 26.56  40.98  41.22 -0.26 1.21

                 S 1 1342 58.86  73.28  73.37 -0.13 1.22

  A64 299.8 286  P 1 1342 28.44  42.86  42.48  0.37 1.16

                 S 1 1342 60.86  75.28  75.61 -0.36 1.17

  A16 300.5 279  P 0 1342 27.99  42.41  42.56 -0.14 1.59

  MIM 305.1 228 EPC3 1342 27.63  42.05  43.13 -1.09 0.14  55 .16  2.9 175  3.1

                 S 4 1342 71.88  86.30  76.77  9.50 0.00

  A11 312.5 274  P 4 1342 30.69  45.11  44.05  1.06 0.00

  LMQ 325.6 280  P 1 1342 31.55  45.97  45.65  0.25 1.12

  SMQ 354.3 353  P 0 1342 34.85  49.27  49.19  0.02 1.40

                 S 1 1342 73.89  88.31  87.56  0.64 0.92

  WVL 396.3 225 EPC2 1342 38.96  53.38  54.38 -1.00 0.31  41 .21  2.9

                 S 4 1342 94.88 109.30  96.79 12.49 0.00

  DAQ 401.6 284  P 1 1342 41.09  55.51  55.03  0.32 0.92

  MNQ 433.1 333  P 2 1342 43.90  58.32  58.93 -0.61 0.51

                 S 1 1342 90.26 104.68 104.90 -0.21 0.84

  DPQ 512.0 265  P 1 1342 54.54  68.96  68.67  0.29 0.63

  NH1 581.7 228 EPC4 1343 10.31  84.73  77.27  7.46 0.00  38 .27  3.2

                 S 4 1343 84.02 158.44 137.54 20.90 0.00

  HNH 612.6 232  S 4 1343 95.85 170.27 144.34 25.88 0.00  58 .46  3.1

  GLO 613.5 217 ES 4 1343 98.00 172.42 144.52 27.90 0.00

  WFM 654.3 221 EP 4 1343 32.10 106.52  86.24 20.28 0.00

  TRQ 656.1 262  P 0 1342 72.03  86.45  86.45  0.00 0.33

                 S 4 1342 77.38  91.80 153.89-62.08 0.00





 NORTHWEST MAINE CRUSTAL STRUCTURE

 99SEP28 NB, MIRAMICHI



  DATE     ORIGIN    LAT N    LONG W   DEPTH   MN  MC  ML GAP   RMS  ERH  ERZ Q

 990928 1847 18.40 46-59.27  66-33.82  16.08  2.8 3.0     144  0.35  1.9  2.1 C



  STN  DIST AZM  RMK HRMN   SEC   TOBS   TCAL   RES   WT AMX PRX XMAG FMP FMAG

  PQI 116.4 252 EPC0 1847 37.37  18.97  18.87  0.07 2.16              131  2.7

                 S 4 1847 49.81  31.41  33.58 -2.23 0.00

  LMN 185.0 133  P 0 1847 46.60  28.20  28.18  0.02 1.89

  GSQ 218.0 349  P 1 1847 51.13  32.73  32.27  0.45 1.29

  A21 249.5 289  P 1 1847 54.31  35.91  36.15 -0.24 1.22

  A16 266.5 282  P 1 1847 56.36  37.96  38.26 -0.30 1.15

  A64 267.9 290  P 4 1847 85.79  67.39  38.43 28.94 0.00

  MIM 272.5 225 EPC3 1847 58.50  40.10  38.99  1.09 0.26  71 .18  2.8 222  3.3

                 S 4 1847 93.53  75.13  69.41  5.69 0.00

  A11 277.3 276  P 3 1847 59.01  40.61  39.59  1.01 0.29

  A61 278.1 286  P 2 1847 57.36  38.96  39.68 -0.73 0.67

  CNQ 280.9 336  P 1 1847 58.17  39.77  40.02 -0.28 1.11

                 S 3 1847 91.67  73.27  71.24  1.97 0.00

  ICQ 286.6 349  P 0 1847 59.46  41.06  40.73  0.32 1.46

  LMQ 291.3 282  P 0 1847 60.05  41.65  41.32  0.26 1.45

                 S 1 1847 91.93  73.53  73.55 -0.14 1.09

  A54 296.3 280  P 1 1847 60.15  41.75  41.93 -0.24 1.06

                 S 1 1847 93.45  75.05  74.64  0.31 1.06

  WVL 364.5 221 EPC4 1848 16.34  57.94  50.35  7.58 0.00  24 .17  2.7

                 S 4 1848 59.06 100.66  89.61 11.03 0.00

  DAQ 368.9 287  P 1 1847 69.30  50.90  50.89 -0.15 0.86

  MNQ 426.0 338  P 2 1848 15.81  57.41  57.94 -0.53 0.44

                 S 3 1848 59.87 101.47 103.13 -1.66 0.01

  DPQ 475.6 266  P 1 1848 21.95  63.55  64.07 -0.52 0.51

                 S 4 1848 69.81 111.41 114.04 -2.63 0.00

  NH1 548.3 226 EPC4 1848 57.34  98.94  73.04 25.90 0.00  19 .20  3.0

  HNH 578.4 231                                           25 .36  2.8

Acknowledgments

We would like to thank the Undergraduate Research Opportunities Program (UROP) of MIT for its support to the network. Our map database has been developed in-house using ARCINFO and in part basemap data provided by ESRI, Inc. (Arcdata Online), USGS GTOPO30 Elevation Data, and TIGER/Line '94, '95, and '97 (US Census Bureau) spatial data.

References

Chaplin, M.P., Taylor, S.R., and Toksöz, M.N. (1980), A coda length magnitude scale for New England, Earthquake Notes, 51, 15-22.

Ebel, J.E. (1982), M_L measurements for northeastern United States earthquakes, Bull. Seism. Soc. Am., 72, 1367-1378.

Rosario, M. (1979), A coda duration magnitude scale for the New England Seismic Network, Master's Thesis, Boston College, 82 pp.