High resolution double-difference relocations of earthquakes in and offshore Puerto Rico and Virgin Islands during the deployment of ocean bottom seismometers from mid-2015 to mid-2016

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Frequently anticipated questions:

What does this data set describe?
Who produced the data set?
Why was the data set created?
How was the data set created?
How reliable are the data; what problems remain in the data set?
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Who wrote the metadata?

What does this data set describe?

Title:

High resolution double-difference relocations of earthquakes in and offshore Puerto Rico and Virgin Islands during the deployment of ocean bottom seismometers from mid-2015 to mid-2016

Abstract:

Puerto Rico is a Caribbean Island with a population of about 3.2 million people who are exposed to natural hazards including earthquakes and submarine landslides that can generate tsunamis. Previous work has shown seismicity offshore Puerto Rico especially between the coastline and the Puerto Rico Trench north of the island. The Puerto Rico Seismic Network maintains the local seismic network to record earthquakes, but these earthquake locations rely on seismic instruments that are all located on land. As part of the assessment of these natural hazards to Puerto Rico and Virgin Islands, six ocean bottom seismometers (OBS) were deployed from mid-2015 to mid-2016 to help understand offshore seismic hazards especially those north of the islands near the Puerto Rico Trench. This data release presents earthquake information recorded during the deployment and attempts to relocate these events by merging the earthquake phase arrival data from the Puerto Rico Seismic Network and the OBS deployment.

Supplemental_Information:

Included are the original P and S phase travel times, list of stations, waveform cross-correlation results, and velocity model used as input for the relocation algorithm/code. A total of six files are included. Time period corresponds to USGS Field Activity 2015-015-FA, https://cmgds.marine.usgs.gov/fan_info.php?fan=2015-015-FA (deployment) and 2016-019-FA, https://cmgds.marine.usgs.gov/fan_info.php?fan=2016-019-FA (recovery).

How might this data set be cited?
Flores, Claudia, 20241022, High resolution double-difference relocations of earthquakes in and offshore Puerto Rico and Virgin Islands during the deployment of ocean bottom seismometers from mid-2015 to mid-2016: data release DOI:10.5066/P13485PX, U.S. Geological Survey, Coastal and Marine Hazards and Resources Program, Woods Hole Coastal and Marine Science Center, Woods Hole, MA.
Online Links:
- https://doi.org/10.5066/P13485PX
- https://www.sciencebase.gov/catalog/item/65a186fcd34e5af967a3f410
Other_Citation_Details:
Suggested citation:Flores, C.H., 2024, High resolution double-difference relocations of earthquakes in and offshore Puerto Rico and Virgin Islands during the deployment of ocean bottom seismometers from mid-2015 to mid-2016: U.S. Geological Survey data release, https://doi.org/10.5066/P13485PX.
What geographic area does the data set cover?
West_Bounding_Coordinate: -69.0000
East_Bounding_Coordinate: -63.0000
North_Bounding_Coordinate: 20.0000
South_Bounding_Coordinate: 17.0000
What does it look like?

https://www.sciencebase.gov/catalog/file/get/65a186fcd34e5af967a3f410?name=PuertoRico_Events_Stations.jpg&allowOpen=true (JPEG)
General map of Puerto Rico and Virgin Islands showing bathymetry (Andrews and others, 2014) and earthquake locations occurring during the ocean bottom seismometer (OBS) deployment from mid-May 2015 to June 2016. Relevant land stations and OBS shown. (Andrews, B.D., ten Brink, U.S., Danforth, W.W., Chaytor, J.D., Granja Bruña, José-Luis, Llanes Estrada, Pilar, and Carbó-Gorosabel, Andrés, 2014, Bathymetric terrain model of the Puerto Rico trench and the northeastern Caribbean region for marine geological investigations: U.S. Geological Survey Open-File Report 2013–1125, 10 p., 1 pl., https://doi.org/10.3133/ofr20131125.)
Does the data set describe conditions during a particular time period?

Beginning_Date: 13-May-2015

Ending_Date: 01-Jun-2016

Currentness_Reference:

The beginning and ending dates represent the time period range of the ocean bottom seismometer deployment.
What is the general form of this data set?
Geospatial_Data_Presentation_Form: tabular digital data
How does the data set represent geographic features?
1. How are geographic features stored in the data set?
  This is a Point data set.
2. What coordinate system is used to represent geographic features?
  Horizontal positions are specified in geographic coordinates, that is, latitude and longitude. Latitudes are given to the nearest 0.0001. Longitudes are given to the nearest 0.0001. Latitude and longitude values are specified in Decimal degrees. The horizontal datum used is World Geodetic System 1984 (WGS 84).
  The ellipsoid used is WGS_1984.
  The semi-major axis of the ellipsoid used is 6378137.0.
  The flattening of the ellipsoid used is 1/298.257223563.
  
  Vertical_Coordinate_System_Definition:
  Altitude_System_Definition:
  Altitude_Datum_Name: North American Vertical Datum of 1988
  Altitude_Resolution: 10.0
  Altitude_Distance_Units: meters
  Altitude_Encoding_Method:
  Explicit elevation coordinate included with horizontal coordinates
  
  Depth_System_Definition:
  Depth_Datum_Name: Mean sea level
  Depth_Resolution: 0.01
  Depth_Distance_Units: kilometers
  Depth_Encoding_Method: Explicit depth coordinate included with horizontal coordinates
How does the data set describe geographic features?

EQ_20150513_20160601.csv
List of earthquake events from May 13, 2015 to June 1, 2016 corresponding to the deployment of six ocean bottom seismometers offshore north of Puerto Rico and Virgin Islands obtained from the ISC (see sources) as reported by the PRSN (see sources). Comma Separated Value (CSV) file with 75785 point features. (Source: Producer Defined)

EVID
Earthquake Event Identification Number, a unique number assigned to each earthquake. (Source: Producer Defined)

Range of values

Minimum: 607235477

Maximum: 610834400

Units: none

Resolution: 1

FLAG
Character flag used for input into the double-difference earthquake relocation software. It is included here to make it easier to reformat the file for processing. See Waldhauser (2001) in cross-references. (Source: Producer Defined) #
YEAR
Earthquake event origin time year in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 2015

Maximum: 2016

Units: time in years

Resolution: 1

MONTH
Earthquake event origin time month in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 1

Maximum: 12

Units: Time in months

Resolution: 1

DAY
Earthquake event origin time day in a given month in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 1

Maximum: 31

Units: Time in days

Resolution: 1

HOUR
Earthquake event origin time hour in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 23

Units: Time in hours

Resolution: 1

MIN
Earthquake event origin time minute in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 59

Units: Time in minutes

Resolution: 1

SEC
Earthquake event origin time seconds in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 59.99

Units: time in seconds

Resolution: 0.01

LATITUDE
Earthquake event location latitude (Source: Producer Defined)

Range of values

Minimum: 17.0682

Maximum: 20.2927

Units: decimal degrees

Resolution: 0.0001

LONGITUDE
Earthquake event location longitude (Source: Producer Defined)

Range of values

Minimum: -69.4868

Maximum: -63.0180

Units: decimal degrees

Resolution: 0.0001

DEPTH
Earthquake event location depth relative to local sea level. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 211.33

Units: kilometers

Resolution: 0.01

MAGNITUDE
Earthquake event Local Magnitude, ML, as assigned by the PRSN (see sources) (Source: Producer Defined)

Value Definition

0.0 Magnitude of event unassigned by the seismic network. A value of 0.0 is used for earthquake relocation processing.

Range of values

Minimum: 2.00

Maximum: 4.60

Units: Local Magnitude

Resolution: 0.01

ERRH
Earthquake location error in the horizontal plane as estimated by the PRSN and reported to the ISC (see sources) (Source: Producer Defined)

Value Definition

0.0000 Unknown horizontal error assigned to earthquake event. A value of 0.0000 is used for earthquake relocation processing.

Range of values

Minimum: 0.0003

Maximum: 0.1826

Units: kilometers

Resolution: 0.0001

ERRZ
Earthquake location error in the vertical plane as estimated by the PRSN and reported to the ISC (see sources) (Source: Producer Defined)

Value Definition

0.0000 Unknown horizontal error assigned to event

Range of values

Minimum: 0.0

Maximum: 0.0

Units: kilometers

Resolution: 0.1

RMS
Earthquake event root mean squared in seconds (Source: Producer Defined)

Value Definition

0.000 Unknown root mean square value for event.

Range of values

Minimum: 0.01

Maximum: 1.50

Units: seconds

Resolution: 0.01

STATION
Seismic station abbreviation code recording a seismic phase for the earthquake event. (Source: Producer Defined) FDSN Station ID code
TRAVELTIME
Seismic phase travel-time; the time in seconds after the earthquake event origin time the identified seismic phase is recorded at the identified station. There are some negative travel-times on a few events on OBS stations. This is a result of a discrepancy between the earthquake event time and location generated from the land stations and the phase arrival found in the OBS. (Source: Producer Defined)

Range of values

Minimum: -4.9702

Maximum: 323.1

Units: seconds

Resolution: 0.0001

WEIGHT
An assigned value between 0 and 1 to indicate the confidence of the seismic phase pick at the identified station. See Process 2 for details on how the pick weight was calculated depending on distance between event and seismic station. (Source: Producer Defined)

Range of values

Minimum: 0.1

Maximum: 1

Units: none

Resolution: 0.01

PHASE
Seismic phase recorded for identified earthquake event at identified seismic station (Source: Producer Defined)

Value Definition

P Primary seismic phase - compressional wave

S Secondary seismic phase - shear wave

EQ_CrossCorrelation.csv
File containing the results of waveform cross-correlation for input into the double difference software. The file contains the elements needed for the software as described in Waldhauser, 2001. Comma Separated Value (CSV) file. (Source: Producer Defined)

FLAG
Character flag used in the HypoDD software, see Waldhauser, 2001 for format descriptions. (Source: Producer Defined) # - Flag
EVID_1
Earthquake event identification number for first event in the waveform cross-correlation (Source: Producer Defined)

Range of values

Minimum: 607243260

Maximum: 610636713

Units: none

Resolution: 1

EVID_2
Earthquake event identification number for second event in the waveform cross-correlation (Source: Producer Defined)

Range of values

Minimum: 607248489

Maximum: 610637960

Units: none

Resolution: 1

ORIGIN_TCorr
Earthquake event origin time correction. It is set to 0.0 for the earthquake relocation process. (Source: Producer Defined)

Range of values

Minimum: 0.0

Maximum: 0.0

Units: seconds

Resolution: 0.1

STATION
Station at which the two identified earthquake events that had their seismic waveforms matched. (Source: Producer Defined) Station abbreviations correspond to the station abbreviations in file Stations.csv.
DT_SEC
Shift in seconds of the second earthquake event to maximize the waveform cross-correlation between the two listed events. A positive number is advancement in time shift, a negative number is reduction in time shift. (Source: Producer Defined)

Range of values

Minimum: -7.03

Maximum: 4.40

Units: seconds

Resolution: 0.01

WGHT
A value between 0.6 to 1 to represent the percentage of similarity between two earthquake event waveforms at the identified station. A value of 1.0 is maximum similarity. (Source: Producer Defined)

Range of values

Minimum: 0.60

Maximum: 1.0

Units: none

Resolution: 0.0001

PHASE
Earthquake event seismic phase compared. (Source: Producer Defined)

Value Definition

P Primary Seismic phase - compressional wave

S Secondary Seismic phase - shear wave

EQ_Relocations_HypoDD.csv
Results of the double-difference earthquake relocation analysis. Of the original 4007 events only 3719 events were relocated. Details of the column output can be found in Waldhauser (2001). Comma Separated Value (CSV) file of 3719 point features. (Source: Producer Defined)

EVID
Earthquake event identification number (Source: Producer Defined)

Range of values

Minimum: 607235477

Maximum: 610739829

Units: none

Resolution: 1

LATITUDE
Earthquake event location latitude (Source: Producer Defined)

Range of values

Minimum: 17.435948

Maximum: 19.753054

Units: decimal degrees

Resolution: 0.000001

LONGITUDE
Earthquake event location longitude (Source: Producer Defined)

Range of values

Minimum: -69.488127

Maximum: -63.116646

Units: decimal degrees

Resolution: 0.000001

DEPTH
Earthquake event location depth relative to local sea level. (Source: Producer Defined)

Range of values

Minimum: 0.01

Maximum: 517.069

Units: kilometers

Resolution: 0.001

C_X
East-West location relative to cluster centroid (Source: Producer Defined)

Range of values

Minimum: -338256.8

Maximum: 228280.6

Units: meters

Resolution: 0.1

C_Y
North-South location relative to cluster centroid (Source: Producer Defined)

Range of values

Minimum: -129281.1

Maximum: 106963.6

Units: meters

Resolution: 0.1

C_Z
depth location relative to cluster centroid, up is positive. Details in Waldhauser and Ellsworth (2000). (Source: Producer Defined)

Value Definition

-9999 No Data

Range of values

Minimum: -37776

Maximum: 479282

Units: meters

Resolution: 0.1

EX
East-West error as calculated by the double-difference algorithm. See details in Waldhauser and Ellsworth (2000). (Source: Producer Defined)

Range of values

Minimum: 506.3

Maximum: 43744.0

Units: meters

Resolution: 0.1

EY
North-South error as calculated by the double-difference algorithm. See details in Waldhauser and Ellsworth (2000). (Source: Producer Defined)

Range of values

Minimum: 337.7

Maximum: 58852.8

Units: meters

Resolution: 0.1

EZ
depth error as calculated by the double-difference algorithm. See details in Waldhauser and Ellsworth (2000). (Source: Producer Defined)

Range of values

Minimum: 431.6

Maximum: 145485.0

Units: meters

Resolution: 0.1

YEAR
Earthquake event origin time year in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 2015

Maximum: 2016

Units: Years

Resolution: 1

MONTH
Earthquake event origin time month in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 1

Maximum: 12

Units: Months

Resolution: 1

DAY
Earthquake event origin time day of the month in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 1

Maximum: 31

Units: Days

Resolution: 1

HOUR
Earthquake event origin time hour in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 23

Units: Hours

Resolution: 1

MINUTE
Earthquake event origin time minutes in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 59

Units: Minutes

Resolution: 1

SECOND
Earthquake origin time seconds in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 0.01

Maximum: 59.99

Units: Seconds

Resolution: 0.01

MAGNITUDE
Earthquake event magnitude as calculated by the PRSN (see sources). (Source: Producer Defined)

Range of values

Minimum: 0.0

Maximum: 4.6

Units: Local Magnitude

Resolution: 0.01

NCCP
Number of waveform cross-correlated P-wave data used in the double difference software. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 0

Units: none

Resolution: 1

NCCS
Number of waveform cross-correlated S-wave data used in the double difference software. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 0

Units: none

Resolution: 1

NCTP
Number of catalog P-wave travel-times used in the double difference software. (Source: Producer Defined)

Range of values

Minimum: 2

Maximum: 309

Units: none

Resolution: 1

NCTS
Number of catalog S-wave trave-time data as used by the double difference software. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 258

Units: none

Resolution: 1

RCC
RMS residual for cross-correlated data as reported by the double difference software (Source: Producer Defined)

Range of values

Minimum: -9.0

Maximum: -9.0

Units: none

Resolution: 1

RCT
RMS residual for travel-time data as reported by the double difference software. (Source: Producer Defined)

Range of values

Minimum: 0.002

Maximum: 2.48

Units: seconds

Resolution: 0.001

CID
Cluster index, number assigned by the double difference software. (Source: Producer Defined)

Range of values

Minimum: 1

Maximum: 41

Units: none

Resolution: 1

EQ_Reviewed_Phases.csv
Dataset of the reviewed earthquake events that range in dates from May 13, 2015 to August 12, 2015. The file is in similar format as original event file EQ_20150513_20160601.csv. The only difference is an additional column "CHANNEL" to define which channel of the seismic station the seismic wave arrival was identified at. Comma Separated Value (CSV) file with 35123 point features. (Source: Producer Defined)

EVID
Event Identification number to uniquely identify the earthquake event. (Source: Producer Defined)

Range of values

Minimum: 607235477

Maximum: 610636713

Units: none

Resolution: 1

FLAG
Character flag used for input into the double-difference software.See Waldhauser, 2001 for description. (Source: Producer Defined) # - flag
YEAR
Earthquake event origin time year in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 2015

Maximum: 2015

Units: time

Resolution: 1

MONTH
Earthquake event origin time month in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 5

Maximum: 8

Units: month

Resolution: 1

DAY
Earthquake event origin time day of the month in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 1

Maximum: 31

Units: day

Resolution: 1

HOUR
Earthquake event origin time hour in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 23

Units: hour

Resolution: 1

MIN
Earthquake event origin time minute in UTC time zone. (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 59

Units: minutes

Resolution: 1

SEC
Earthquake event origin time seconds in UTC time zone (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 59.9

Units: seconds

Resolution: 0.01

LATITUDE
Earthquake event location latitude (Source: Producer Defined)

Range of values

Minimum: 17.0682

Maximum: 19.9335

Units: decimal degrees

Resolution: 0.0001

LONGITUDE
Earthquake event location longitude (Source: Producer Defined)

Range of values

Minimum: -69.0115

Maximum: -63.1800

Units: decimal degrees

Resolution: 0.0001

DEPTH
Earthquake event location depth (Source: Producer Defined)

Range of values

Minimum: 0

Maximum: 183.99

Units: kilometers

Resolution: 0.01

MAGNITUDE
Earthquake event local magnitude, ML, as assigned by the PRSN (see sources) (Source: Producer Defined)

Value Definition

0.0 Unknown earthquake magnitude

Range of values

Minimum: 2.0

Maximum: 4.3

Units: Local Magnitude (logomithmic scale)

Resolution: 0.1

ERRH
Earthquake event error in the horizontal plane. (Source: Producer Defined) The horizontal location error is undefined due to not recalculating the earthquake event error with the additional P and S wave data.
ERRZ
Earthquake event error in the vertical direction (Source: Producer Defined) The vertical location error is undefined due to not recalculating the earthquake event error with the additional P and S wave data.
RMS
Earthquake event root mean squared - RMS in seconds. (Source: Producer Defined) The RMS error is undefined due to not recalculating the earthquake event error with the additional P and S wave data.
STATION
seismic station abbreviation code recording a seismic phase for the earthquake event. See Ringler and Evans (2015) for explanation. (Source: Producer Defined) FNDS Station ID code
TRAVELTIME
Seismic phase travel-time; the time in seconds after the earthquake event origin time the identified seismic phase is recorded at the identified seismic station. (Source: Producer Defined)

Range of values

Minimum: 0.90

Maximum: 4549.12

Units: seconds

Resolution: 0.01

WEIGHT
An assigned value between 0 and 1 to indicate the confidence of the seismic phase identified at the station. For this file it is set at 0.9. (Source: Producer Defined)

Range of values

Minimum: 0.9

Maximum: 0.9

Units: none

Resolution: 0.1

PHASE
Seismic phase recorded for identified earthquake event at identified station (Source: Producer Defined)

Value Definition

P Primary seismic phase - compressional wave

S Secondary seismic phase - shear wave

CHANNEL
Seismometer Channel used to identify the seismic phase. (Source: Producer Defined) A seismic station has three channel components that are orthogonal to each other. A seismometer also records at defined sample rate. The channel code helps identify which component and at what sample rate a seismic wave arrival was detected. For a list of commonly used codes see Ringler and Evans (2015).

Stations.csv
List of seismic stations that contributed seismic phase data to the original location of the earthquakes in the list. This same list is used as input for the double-difference earthquake relocation software. Comma Separated Value (CSV) file with 168 point features. (Source: Producer Defined)

Station
Unique seismic station name as a three to four letter code. See Ringer and Evans (2015) in cross-references for an explanation. (Source: Producer Defined) Three to Four letter station code given the by seismic network and listed under the International Registry of Seismograph Stations.See Ringer and Evans (2015) in cross-references.
Network
Seismic network code for the seismic station (Source: Producer Defined)

Value Definition

n/a Network Code unknown or unassigned

Two letter network abbreviation the station belongs to recognized by the FDSN - the International Federation of Digital Seismograph Networks. https://www.fdsn.org/ See Ringler and Evans (2015) for explanation.
Latitude
Station location latitude (Source: Producer Defined)

Range of values

Minimum: 5.224

Maximum: 32.9075

Units: decimal degrees

Resolution: 0.000001

Longitude
Station location longitude (Source: Producer Defined)

Range of values

Minimum: -84.9525

Maximum: -59.4579

Units: decimal degrees

Resolution: 0.000001

Elevation
Station location elevation or depth. Positive is up. (Source: Producer Defined)

Range of values

Minimum: -5426.3

Maximum: 3697.0

Units: meters

Resolution: 0.1

VelocityModel.csv
Velocity model used for the double-difference earthquake relocation, (Waldhauser, 2001). It combines the shallow, less than 31 km, velocity model from the Mendoza Model with the IASP91 velocity model (see sources) below 31 km. This model extends it to 250 km depth.Comma Separated Value (CSV) file with 20 rows. (Source: Producer Defined)

TOP-KM
Depth to the top of the defined seismic P-wave velocity layer. Positive is down. (Source: Producer Defined)

Range of values

Minimum: -3.0

Maximum: 250.0

Units: Kilometers

Resolution: 0.1

P-Velocity
Seismic P-phase velocity (Source: Producer Defined)

Range of values

Minimum: 6.45

Maximum: 8.45

Units: kilometers/second

Resolution: 0.01

Poisson-Ratio
Poisson ratio, vp/vs, for the defined seismic layer (Source: Producer Defined)

Range of values

Minimum: 1.72

Maximum: 1.84

Units: none

Resolution: 0.01

Entity_and_Attribute_Overview:
This data release contains six CSV files. Event Identification numbers are not necessarily in chronological order. To subsample a selection of events by time, it is suggested to use the event origin time instead of event identification number. EQ_20150513_20160601.csv - Original list of earthquake events (4007 events). EQ_CrossCorrelation.csv - List of paired earthquake events based on their waveform similarity >=60%. EQ_Relocations_HypoDD.csv - List of earthquake events that successfully relocated using the double difference algorithm (Waldhauser, 2001). (3719 events) EQ_Reviewed_Phases.csv - List of events, a subsection of EQ_20150513_20160601 only from May 13, 2015 to August 13, 2015, where existing P and S arrivals were reviewed and new P and S phases are added.(1038 events) Stations.csv - List of stations used for the double-difference algorithm VelocityModel.csv - Seismic velocity model used for the double-difference algorithm processing.
Entity_and_Attribute_Detail_Citation: U.S. Geological Survey

Range of values
Minimum:	607235477
Maximum:	610834400
Units:	none
Resolution:	1

Range of values
Minimum:	2015
Maximum:	2016
Units:	time in years
Resolution:	1

Range of values
Minimum:	1
Maximum:	12
Units:	Time in months
Resolution:	1

Range of values
Minimum:	1
Maximum:	31
Units:	Time in days
Resolution:	1

Range of values
Minimum:	0
Maximum:	23
Units:	Time in hours
Resolution:	1

Range of values
Minimum:	0
Maximum:	59
Units:	Time in minutes
Resolution:	1

Range of values
Minimum:	0
Maximum:	59.99
Units:	time in seconds
Resolution:	0.01

Range of values
Minimum:	17.0682
Maximum:	20.2927
Units:	decimal degrees
Resolution:	0.0001

Range of values
Minimum:	-69.4868
Maximum:	-63.0180
Units:	decimal degrees
Resolution:	0.0001

Range of values
Minimum:	0
Maximum:	211.33
Units:	kilometers
Resolution:	0.01

Value	Definition
0.0	Magnitude of event unassigned by the seismic network. A value of 0.0 is used for earthquake relocation processing.

Range of values
Minimum:	2.00
Maximum:	4.60
Units:	Local Magnitude
Resolution:	0.01

Value	Definition
0.0000	Unknown horizontal error assigned to earthquake event. A value of 0.0000 is used for earthquake relocation processing.

Range of values
Minimum:	0.0003
Maximum:	0.1826
Units:	kilometers
Resolution:	0.0001

Value	Definition
0.0000	Unknown horizontal error assigned to event

Range of values
Minimum:	0.0
Maximum:	0.0
Units:	kilometers
Resolution:	0.1

Value	Definition
0.000	Unknown root mean square value for event.

Range of values
Minimum:	0.01
Maximum:	1.50
Units:	seconds
Resolution:	0.01

Range of values
Minimum:	-4.9702
Maximum:	323.1
Units:	seconds
Resolution:	0.0001

Range of values
Minimum:	0.1
Maximum:	1
Units:	none
Resolution:	0.01

Value	Definition
P	Primary seismic phase - compressional wave
S	Secondary seismic phase - shear wave

Range of values
Minimum:	607243260
Maximum:	610636713
Units:	none
Resolution:	1

Range of values
Minimum:	607248489
Maximum:	610637960
Units:	none
Resolution:	1

Range of values
Minimum:	0.0
Maximum:	0.0
Units:	seconds
Resolution:	0.1

Range of values
Minimum:	-7.03
Maximum:	4.40
Units:	seconds
Resolution:	0.01

Range of values
Minimum:	0.60
Maximum:	1.0
Units:	none
Resolution:	0.0001

Value	Definition
P	Primary Seismic phase - compressional wave
S	Secondary Seismic phase - shear wave

Range of values
Minimum:	607235477
Maximum:	610739829
Units:	none
Resolution:	1

Range of values
Minimum:	17.435948
Maximum:	19.753054
Units:	decimal degrees
Resolution:	0.000001

Range of values
Minimum:	-69.488127
Maximum:	-63.116646
Units:	decimal degrees
Resolution:	0.000001

Range of values
Minimum:	0.01
Maximum:	517.069
Units:	kilometers
Resolution:	0.001

Range of values
Minimum:	-338256.8
Maximum:	228280.6
Units:	meters
Resolution:	0.1

Range of values
Minimum:	-129281.1
Maximum:	106963.6
Units:	meters
Resolution:	0.1

Value	Definition
-9999	No Data

Range of values
Minimum:	-37776
Maximum:	479282
Units:	meters
Resolution:	0.1

Range of values
Minimum:	506.3
Maximum:	43744.0
Units:	meters
Resolution:	0.1

Range of values
Minimum:	337.7
Maximum:	58852.8
Units:	meters
Resolution:	0.1

Range of values
Minimum:	431.6
Maximum:	145485.0
Units:	meters
Resolution:	0.1

Range of values
Minimum:	2015
Maximum:	2016
Units:	Years
Resolution:	1

Range of values
Minimum:	1
Maximum:	12
Units:	Months
Resolution:	1

Range of values
Minimum:	1
Maximum:	31
Units:	Days
Resolution:	1

Range of values
Minimum:	0
Maximum:	23
Units:	Hours
Resolution:	1

Range of values
Minimum:	0
Maximum:	59
Units:	Minutes
Resolution:	1

Range of values
Minimum:	0.01
Maximum:	59.99
Units:	Seconds
Resolution:	0.01

Range of values
Minimum:	0.0
Maximum:	4.6
Units:	Local Magnitude
Resolution:	0.01

Range of values
Minimum:	0
Maximum:	0
Units:	none
Resolution:	1

Range of values
Minimum:	0
Maximum:	0
Units:	none
Resolution:	1

Range of values
Minimum:	2
Maximum:	309
Units:	none
Resolution:	1

Range of values
Minimum:	0
Maximum:	258
Units:	none
Resolution:	1

Range of values
Minimum:	-9.0
Maximum:	-9.0
Units:	none
Resolution:	1

Who produced the data set?

Who are the originators of the data set? (may include formal authors, digital compilers, and editors)
- Claudia Flores
Who also contributed to the data set?
Uri ten Brink & Nathan Miller. (2015). USGS Puerto Rico Trench [Data set]. International Federation of Digital Seismograph Networks. https://doi.org/10.7914/SN/ZZ_2015
To whom should users address questions about the data?

Claudia Flores

U.S. Geological Survey, Northeast Region

Geophysicist

384 Woods Hole Road
Woods Hole, MA

US

508-548-8700 x2391 (voice)

cflores@usgs.gov

Why was the data set created?

A deployment of six ocean bottom seismometers offshore northern Puerto Rico and Virgin Islands collected seismic data from mid-2015 to mid-2016 with the intent of improving earthquake locations offshore Puerto Rico and identifying areas of persistent seismicity, sometimes identified as earthquake swarms. To understand the potential bias of locating earthquakes using only land based seismometers, seismic data from ocean bottom seismometers are merged with the land based seismic data. Earthquake relocated calculations are conducted with the merged seismic data of earthquakes that were recorded contemporaneously. The collection includes the earthquake locations before and after applying the Double-Difference algorithm, velocity model, seismic stations, calculated waveform cross-correlations and finally a selection of reviewed earthquakes.

How was the data set created?

From what previous works were the data drawn?
PRSN (source 1 of 5)
Puerto, University of Rico, 1986, Puerto Rico Seismic Network & Puerto Rico Strong Motion Program: International Federation of Digital Seismograph Networks, n/a.
Online Links:
- https://doi.org/10.7914/SN/PR
Type_of_Source_Media: QuakeML and text, digital
Source_Contribution:
Original contributor of the list of earthquake events with their origin times and locations that were reported to the ISC. Contributor to seismic station waveforms.
ISC (source 2 of 5)
Centre, International Seismological, 2017, ISC: International Seismological Centre (2017), On-line Bulletin.
Online Links:
- https://doi.org/10.31905/D808B830
Other_Citation_Details: On-line Bulletin accessed 2017 to 2018.

Type_of_Source_Media: QuakeML and text, online
Source_Contribution:
List of earthquake events with their origin times and locations. In addition a listing of associated P-wave and S-wave phases at times recorded at individual seismic stations.
IASP91 (source 3 of 5)
B. L. N. Kennett, and Engdahl, E. R., 19910501, Traveltimes for global earthquake location and phase identification: Geophysical Journal International vol. 105, issue 2, Oxford University Press (OUP), n/a.
Online Links:
- https://doi.org/10.1111/j.1365-246X.1991.tb06724.x
Other_Citation_Details: ppg. 429-465

Type_of_Source_Media: Digital
Source_Contribution:
Reference used in predicting seismic phase arrivals and reference seismic velocity model.
PR OBS (source 4 of 5)
Brink, Uri ten, and Miller, Nathan, 2015, USGS Puerto Rico Trench: International Federation of Digital Seismograph Networks, n/a.
Online Links:
- https://doi.org/10.7914/sn/zz_2015
Other_Citation_Details:
Corresponds to USGS Field Activity Numbers 2015-015-FA and 2016-019-FA

Type_of_Source_Media: Digital
Source_Contribution:
Original waveforms from the ocean bottom seismometer deployment.
Mendoza Model (source 5 of 5)
Mendoza, Carlos, and McCann, William R., 2005, Improving the Seismic Hazard Model for Puerto Rico through Seismic Tomography and a Reliable Microearthquake Catalog With Recalculated Magnitudes and Calibrated Hypocentral Error Estimates: Collaborative Research with W. McCann and C. Mendoza: Earthquake Hazards Program External Grants, n/a.
Online Links:
- https://earthquake.usgs.gov/cfusion/external_grants/reports/05HQGR0012.pdf
Other_Citation_Details: Grant Award Number 05HQGR0012

Type_of_Source_Media: Digital
Source_Contribution:
Seismic velocity module for Puerto Rico, the upper 31 kilometers.
How were the data generated, processed, and modified?
Date: 09-Jan-2017 (process 1 of 5)
Process Step 1: The original earthquake event data was downloaded online from the International Seismic Centre - ISC. This was saved as both as text and QuakeML files. The information downloaded is the event origin time and location, depth, magnitude, location errors if any, associated P and S-waves of the event at seismic stations. To obtain the event list information, the following search parameters were submitted: Latitude ranges 16.5 to 20.5 degrees north, Longitude ranges -69.5 to -63.0 degrees, all available depths and earthquake local magnitudes, ML, with start date of 2015-05-13 00:00:00 to end date of 2016-06-01 23:59:59. A total of 4007 earthquake events are in this list. This process step and all subsequent process steps were performed by the same person, Claudia Flores, unless otherwise noted. Person who carried out this activity:

Claudia Flores

U.S. Geological Survey, Northeast Region

Geophysicist

384 Woods Hole Road
Woods Hole, MA

US

508-548-8700 x2391 (voice)

cflores@usgs.gov

Data sources used in this process:
- ISC
- PRSN
Data sources produced in this process:
- Earthquake Origin Data
Date: 16-Aug-2017 (process 2 of 5)
Process Step 2: Picking Seismic Phases from the known events on the Ocean Bottom Seismometers - OBS. Python version 3.6.7 and ObsPY version 1.1.1 (Beyreuther et al., 2010) are the main tools used to manipulate seismic waveforms and make calculations. Using the known locations of the earthquake events from the PRSN and the IASP91 velocity model, a list of predicted seismic phase arrivals for the OBS are calculated for input into an auto-picker. FBpicker is a module inside the Python software tool PhasePApy (Chen and Holland, 2015) that is used to pick the P-wave arrivals on the OBS. The same code was used for S-wave phases, but problems arose due to the noise from P-wave arrivals conflicting with the predicted S-wave arrival, therefore auto-picking S-wave phases was abandoned. The file EQ_20150513_20160601.csv merges both the known P and S wave arrivals from the ISC, PRSN (see sources) from Step 1, and the auto-picked P-wave arrivals from the OBS stations. An additional piece of information missing from the ISC, PRSN and OBS pick data is the confidence of the seismic wave pick. An assigned picking weight was calculated based on the distance between the seismic station and the earthquake event in degrees. For distances less than 1.0 degrees a pick weight of 1.0 is assigned. For distances between 1.0 to 2.0 degrees, a pick weight is determined by the following function where: pick weight = COS(distance in degrees/0.0238), which results in a range of pick weights between 1 to 0.10. For distances equal or greater than 2.0 degrees a weight of 0.10 is assigned. One decimal degree is approximately 111.19 km. Data sources used in this process:
- IASP91
- PR OBS
Data sources produced in this process:
- OBS P-phase arrivals
Date: 05-May-2018 (process 3 of 5)
Process Step 3: Waveform Cross-Correlation calculations on select PRSN stations and OBS stations. The purpose of waveform cross-correlation is to provide a similarity percentage between earthquake events recorded at a seismic station. The more similar two waveforms recorded at a seismic station, the more likely that the two events originated from the same area. Waveform cross-correlations were calculated by matching waveforms at each station for the events with the restriction that event hypocenters compared cannot be more than 50 km from each other, and a match is considered above 60% similarity between waveforms. All waveforms were filtered using a Butterworth filter with corners between 4 - 16 Hz and cut at 20 seconds starting at 5 seconds before making the event comparisons at each station. PRSN stations used in the cross-correlation are selected based on the noise level observed in the seismic waveform after filtering. Results are in the file EQ_CrossCorrelation.csv. Data sources used in this process:
- Earthquake Origin Data
- OBS P-phase arrivals
- PRSN
- PR OBS
Data sources produced in this process:
- Waveform X-Corr
Date: 30-May-2018 (process 4 of 5)
Process Step 4: Earthquake Relocation using Double-Difference Algorithm. The data from the previous processing steps, the earthquake event information and corresponding waveform cross-correlations, were input for the earthquake relocation code HypoDD version 2.1b. See Waldhauser (2001) for details on how to use the HypoDD software and Waldhauser and Ellsworth (2000) for the double-difference algorithm details. The results depend on a seismic velocity model, and one was developed that combined the velocity model from the Mendoza Model (see sources) for depths to 31 kilometers depth and the IASP91 velocity model for depths 32 to 250 kilometers, included in file VelocityModel.csv. All 4007 events were used as input and the conjugate gradients method for solving the equations to handle the large volume of events. Details on methods for solving the double-difference algorithm are discussed both in Waldhauser and Ellsworth (2000) and Waldhauser (2001). Of the original 4007 events only 3719 events were relocated and are in the file EQ_Relocations_HypoDD.csv. Data sources used in this process:
- Earthquake Origin Data
- OBS P-phase arrivals
- Waveform X-Corr
- Mendoza Model
- IASPI91
Date: 13-Feb-2019 (process 5 of 5)
Process Step 5: Review of seismic phase arrivals on a subsection of the full earthquake event list. Due to time constraints in reviewing each event only a total of 1038 events ranging from May 13, 2015 to August 13, 2015. The purpose of reviewing each event was to add additional P and S phase data that were missed by the auto-picking methods. The auto-picking method generated a P to S pick ratio of 14042:8561. After human review, the P to S pick ratio improved to 18218:16905 for the same number of events. Snuffler, a module inside the seismic processing software Pyrocko version 2019.05.03, is used to import waveforms from various seismic stations sorted by distance to visually inspect each earthquake event and associated seismic wave arrivals (Heimann, et al, 2017). The output from the software is reformatted into a file for purposes of distribution, EQ_Reviewed_Phases.csv. Data sources used in this process:
- PRSN
- OBS P-phase arrivals
- ISC
- PR OBS
What similar or related data should the user be aware of?
Waldhauser, Felix, 2001, hypoDD-A Program to Compute Double-Difference Hypocenter Locations: Open-File Report 2001-113, U.S. Geological Survey, Reston, VA.
Online Links:
- https://doi.org/10.3133/ofr01113
Other_Citation_Details:
HypoDD is a Fortran computer program package for relocating earthquakes with the double-difference algorithm of Waldhauser and Ellsworth (2000). The version used for this dataset is 2.1b.
Chen, Chen, and Holland, Austin A., 20160831, PhasePApy: A Robust Pure Python Package for Automatic Identification of Seismic Phases: Seismological Research Letters Vol. 87, No. 6, Seismological Society of America, n/a.
Online Links:
- https://doi.org/10.1785/0220160019
Other_Citation_Details:
pp. 1384-1396, Software is available at: https://github.com/austinholland/PhasePApy Used the module FBpicker which is part of the software package.
Heimann, Sebastian, Kriegerowski, Marius, Isken, Marius, Cesca, Simone, Daout, Simon, Grigoli, Francesco, Juretzek, Carina, Mergies, Tobias, Nooshiri, Nima, Steinberg, Andreas, Sudhaus, Henriette, Vasyura-Bathke, Hannes, Willey, Timothy, and Dahm, Torsten, 20170629, Pyrocko - An open-source seismology toolbox and library: GFZ Data Services, Potsdam, Germany.
Online Links:
- https://doi.org/10.5880/GFZ.2.1.2017.001
Other_Citation_Details:
Project Website: https://pyrocko.org/ Used the module Snuffler that is part of the software package.
Waldhauser, Felix, and Ellsworth, William L., 20001201, A Double-Difference Earthquake Location Algorithm: Method and Application to the Northern Hayward Fault, California: Bulletin of the Seismological Society of America Vo. 9, No. 6, Seismological Society of America, n/a.
Online Links:
- https://doi.org/10.1785/0120000006
Other_Citation_Details:
pp. 1353-1368, Background information on the algorithm behind the software HypoDD - https://doi.org/10.3133/ofr01113
Willemann, Raymond J., and Storchak, Dmitry A., 20010701, Data Collection at the International Seismological Centre: Seismological Research Letters vol. 72, issue 4, Seismological Society of America (SSA), n/a.
Online Links:
- https://doi.org/10.1785/gssrl.72.4.440
Other_Citation_Details: pp. 440-453, Data collection details
Ringler, Adam T., and Evans, John R., 20150923, A Quick SEED Tutorial: Seismological Research Letters vol. 86, issue 6, Seismological Society of America (SSA), n/a.
Online Links:
- https://doi.org/10.1785/0220150043
Other_Citation_Details: pp. 1717-1725, Table 1 Common Channel-Naming Convetions.
Beyreuther, Moritz, Barsch, Robert, Krischer, Lion, Megies, Tobias, Behr, Yannik, and Wassermann, Joachim, 20100513, ObsPy: A Python Toolbox for Seismology: Seismological Research Letters vol. 81, issue 3, Seismological Society of America (SSA), n/a.
Online Links:
- https://doi.org/10.1785/gssrl.81.3.530
Other_Citation_Details: pp. 530-533

How reliable are the data; what problems remain in the data set?

How well have the observations been checked?
How accurate are the geographic locations?
The downloaded data from the catalogs have location errors assigned to them by the seismic networks. The value of the error depends on the following: the number of stations that detected the event, the quality of the seismic phase identified at the station, the velocity model used to locate the earthquake, and the distance and size of the earthquake with respect to each station that detected it. The Puerto Rico Seismic Network estimates a horizontal and vertical location error and earthquake origin time RMS, root mean squared, based on these variables. The relocation data adds another two sets of variables to increase the accuracy of the earthquake locations: the similarity between earthquake waveforms at individual stations and the similar travel-times between a pair of earthquakes to detecting stations. There is also the addition of six ocean bottom seismometers to help refine these earthquake relocations. Errors are included in the files.
How accurate are the heights or depths?
The downloaded data from the catalogs have location errors assigned to them by the seismic networks. The value of the error depends on the following: the number of stations that detected the event, the quality of the seismic phase identified at the station, the velocity model used to locate the earthquake, and the distance and size of the earthquake with respect to each station that detected it. The Puerto Rico Seismic Network estimates a horizontal and vertical location error and earthquake origin time RMS, root mean squared, based on these variables. The relocation data adds another two sets of variables to increase the accuracy of the earthquake locations: the similarity between earthquake waveforms at individual stations and the similar travel-times between a pair of earthquakes to detecting stations. There is also the addition of six ocean bottom seismometers to help refine these earthquake relocations. Errors are included in the files.
Where are the gaps in the data? What is missing?
The earthquake event data is limited to the data range of May 13, 2015 to June 2, 2016 and a location range of Latitudes between 16.5 to 20.5 degrees and Longitudes from -69.5 to -63.0 degrees. All depths and magnitudes are included. Earthquake phase data include both P and S waves. The ISC established methods for determining completeness of the downloaded data was used for acquiring the source dataset (Willemann, and Storchak, 2001).
How consistent are the relationships among the observations, including topology?
In the process step, we refined the earthquake locations; events were plotted spatially and with respect to depth to compare with the original locations. The only check for data duplication and omission was in the reviewed earthquake event data set. Each event was checked to have seismic wave picks at the stations originally listed from the downloaded data, EQ_Reviewed_Phases.csv.

How can someone get a copy of the data set?

Are there legal restrictions on access or use of the data?

Access_Constraints	None. Please see 'Distribution Info' for details.
Use_Constraints	None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations.

Who distributes the data set? (Distributor 1 of 1)

GS ScienceBase

U.S. Geological Survey

Denver Federal Center, Building 810, Mail Stop 302
Denver, CO

United States

1-888-275-8747 (voice)

sciencebase@usgs.gov
What's the catalog number I need to order this data set?
What legal disclaimers am I supposed to read?
Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty.

How can I download or order the data?

Availability in digital form:

Data format:	The dataset contains six CSV files and the accompanying CSDGM metadata. The transfer size refers to the compressed zip format of all the records. Uncompressed individual file sizes vary ranging from 7 MB to less than 0.5 MB. in format CSV (version Text editors such as Notepad in Windows or VIM and TextEdit in MacOS.) Size: 2
Network links:	https://doi.org/10.5066/P13485PX https://www.sciencebase.gov/catalog/item/65a186fcd34e5af967a3f410 https://www.sciencebase.gov/catalog/file/get/65a186fcd34e5af967a3f410

Cost to order the data: None

What hardware or software do I need in order to use the data set?
The user must have software capable of uncompressing the ZIP file and reading the data formats.

Who wrote the metadata?

Dates:

Last modified: 22-Oct-2024

Metadata author:

Claudia Flores

U.S. Geological Survey, Northeast Region

Geophysicist

384 Woods Hole Road

Woods Hole, MA

508-548-8700 x2391 (voice)

508-457-2310 (FAX)

whsc_data_contact@usgs.gov

Contact_Instructions:

The metadata contact email address is a generic address in the event the person is no longer with the USGS.

Metadata standard:

FGDC Content Standards for Digital Geospatial Metadata (FGDC-STD-001-1998)

This page is <https://cmgds.marine.usgs.gov/catalog/whcmsc/SB_data_release/DR_P13485PX/CFlores_DoubleDifference.faq.html>

Range of values
Minimum:	-69.0115
Maximum:	-63.1800
Units:	decimal degrees
Resolution:	0.0001

Range of values
Minimum:	5.224
Maximum:	32.9075
Units:	decimal degrees
Resolution:	0.000001

Range of values
Minimum:	-84.9525
Maximum:	-59.4579
Units:	decimal degrees
Resolution:	0.000001

Range of values
Minimum:	6.45
Maximum:	8.45
Units:	kilometers/second
Resolution:	0.01