psvelo: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/psvelo - from package: GMT

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/lib/gmt/bin/psvelo - from package: GMT

You may install the required package with command apt-get install {package}

Error in other languages:
psvelo: bevel nie gevind nie
psvelo: comandă negăsită
psvelo: comando não encontrado
psvelo: commande introuvable
psvelo: command not found
psvelo: käsku ei ole
psvelo: không tìm thấy lệnh
psvelo: komanda nerasta
psvelo: Kommando nicht gefunden.
psvelo: kommandot finns inte
psvelo: komut yok
psvelo: nie znaleziono polecenia
psvelo: níor aimsíodh an t-ordú
psvelo: no se encontró la orden
psvelo: no s'ha trobat l'ordre
psvelo: opdracht niet gevonden
psvelo: parancs nem található
psvelo: perintah tidak ditemukan
psvelo: príkaz nenájdený
psvelo: příkaz nenalezen
psvelo: команда не найдена
psvelo: командата не е открита
psvelo: 命令找不到
psvelo: コマンドが見つかりません