MAPPING THE MOHO UNDERNEATH BROADBAND SEISMOGRAPHIC STATIONS OF THE
LAMONT COOPERATIVE SEISMOGRAPHIC NETWORK IN THE NORTHEASTERN UNITED
STATES

ARMBRUSTER, J., Lamont-Doherty Earth Observatory of Columbia
University, Palisades, NY 10964; CROOKER, B., Fordham University, the
Bronx, NY 10458; BROWN, M., Central Park Conservancy, New York, NY
10022; MILLER, C., William Annin Middle School, Basking Ridge, NJ; V.
CORMIER, V., University of Connecticut, Storrs, CT 06269; MINKEL, D.,
Adirondack Community College, Queensbury, NY 12804; SOL, S., Lehigh
University, Bethlehem, PA 18015; KIM, W.-Y., LDEO, Palisades, NY
10964.

The Lamont Cooperative Seismic Network (LCSN) now consists of 21
broadband seismographic stations in New York, Connecticut, New Jersey,
Pennsylvania, Delaware and Maryland operated by 25 cooperating
partners, with Lamont-Doherty Earth Observatory (LDEO) serving as the
lead institution.  These broadband stations, mostly deployed since the
spring of 2000, now provide sufficient waveform data to carry out
quantitative analysis for education and scientific research. We report
our first collective work on receiver function analysis to determine
the Moho depth underneath each station.  This exercise motivates the
LCSN partners to utilize seismic data collected by the network and
achieve its goal of using the seismic data for evaluating the
earthquake hazards in the region.  Preliminary receiver function
analysis of several stations along New York City to Lehigh Valley in
Pennsylvania suggest that Moho depth is about 34 km beneath the Bronx,
Manhattan, and Palisades, and it gradually increases to about 42 km
beneath Basking Ridge, NJ and Lehigh, Pennsylvania going westward.
This suggests an ~8 km increase of the Moho depth along 130 km distance
from the east to the west (from the Bronx to Lehigh), which corresponds
to ~3.5 degree slope for a flat Moho.  Back-azimuth gathers of receiver
functions at Basking Ridge, NJ suggest that the Moho might locally dip
to the southeast by as much as 20 degrees.  The Ps phase, P to S
converted phase at the Moho, samples very close to the station (~6 to
10 km), and is the most prominent phase sampling the lateral
structure.  Since the LCSN broadband stations cover a region with a
diverse geological environment - Newark basin, Appalachian, Adirondacks
and Avalonian from the south to the north, we expect that the receiver
function analysis will provide very interesting results.